JP7389446B2 - Encryption/decryption device, encryption/decryption method, and computer program for executing the method - Google Patents

Description

The present invention relates to digital data encryption and decryption technology, and in particular to a device having a digital data encryption/decryption function, a digital data encryption/decryption method, and a digital data encryption/decryption method that enables a computer to perform digital data encryption/decryption. This invention relates to a program for realizing a decryption function.

Currently, a huge amount of digital data is stored as a resource on various sites on the Internet and is used by people. For example, many websites provide web pages that include digital content (digital data) such as digitized documents, illustrations, photographs, and videos. Furthermore, some websites offer services (so-called internet distribution services) for distributing digital content such as comics and videos to users with specific client systems.

Such digital content generally has a copyright attached to it, and from the perspective of copyright protection, it is necessary to prevent unauthorized use by third parties. In particular, in digital content distribution services, distribution of pirated copies due to unauthorized copying of digital content is a major problem. For this reason, for example, a website can be accessed only by authorized users who have registered as users, and can only be used for streaming, or the digital content itself may be encrypted and a key (access key) must be provided. A method is adopted in which only authorized users can decrypt (decipher) the data. Various methods have been proposed as such encryption and decryption techniques.

For example, Patent Document 1 listed below discloses a method for encrypting graphical objects. Specifically, the encryption device of Patent Document 1 receives a graphical object, generates a secret function set using a secret key K, selects an encryption function from the secret function set, and generates an encrypted graphical object. Encrypting the graphical object using the encryption function to obtain the object and outputting the encrypted graphical object and a representation of the selected encryption function.

JP2014-85674A

With the progress of the information society, the need for encryption/decryption of digital data has increased, and various methods have been proposed. However, when attempting to achieve stronger encryption, there are problems in that the encryption procedure becomes complicated and the computational load increases.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an encryption/decryption technique that can perform robust and high-speed encryption/decryption processing of digital data while keeping the calculation load low.

Another object of the present invention is to provide encryption/decryption processing suitable for performing calculations on a GPU.

Another object of the present invention is to provide a technology that can encrypt digital data without changing the file format of the digital data.

The present invention for solving the above problems is configured to include the following invention specific matters or technical features.

That is, the present invention according to a certain aspect may be a system including an encryption device for encrypting a digital data string to be encrypted. The encryption device includes an acquisition unit that acquires a first data file including the digital data string to be encrypted, and an encryption key that includes at least one unit key consisting of n elements having a permuted relationship. Using the generated encryption key for the element value of the encryption target array corresponding to at least one predetermined area constituting the digital data string that is the encryption target, an encryption processing unit that calculates at least one encrypted sequence by applying a permutation mapping; and a second data file that includes an encrypted digital data string indicated by the calculated at least one encrypted sequence. The output control unit may include an output control unit that performs control for outputting to an output destination. Here, the set of the encryption target array and the permutation mapping may be a group that satisfies the conditions of an associative law, the existence of an identity element, and the existence of an inverse element. Further, the permutation mapping converts the value of the i-th element of the encryption target array, which is indicated by the value Xi (i∈n) of one unit key element in the encryption key, into the i-th element of the encryption array. can be a binary operation that sets the value of the element of .

The encryption processing unit also includes an area dividing unit that divides the digital data string to be encrypted and sets a plurality of predetermined areas, and an encryption target corresponding to each of the plurality of predetermined areas. The computer may further include an arithmetic unit that calculates each of a plurality of encrypted arrays by applying the permutation mapping to the element values of the array using the encryption key.

The encryption processing unit may further include an enlarged area setting unit that sets an enlarged area based on some of the plurality of predetermined areas as a new predetermined area. In addition, the calculation unit applies the permutation mapping to the previously calculated element value of the encrypted array corresponding to the new predetermined area using the encryption key. It is possible to calculate an encrypted sequence.
Further, the encryption processing unit is configured to repeat setting of an enlarged area by the enlarged area setting unit and calculation of an encryption array by the calculation unit in accordance with N-fold encryption.

The encryption device also includes a user key generation unit that generates a user key including at least one unit key made up of n elements having a permutation relationship, and an inverse mapping key of the encryption key and the user key. The apparatus may further include an auxiliary key generation unit that generates an auxiliary key based on the information.

The encryption device outputs a first distribution key based on the user key and a second distribution key based on the auxiliary key to the outside in order to enable decryption of the encrypted digital data string. may be configured.

The first distribution key may be an inverse image of the user key, and the second distribution key may be an inverse mapping of the encryption key.

Further, the present invention according to another aspect further includes a decryption device that decrypts the digital data string encrypted by the encryption device based on the first distribution key and the second distribution key. It can be a system.

The decryption device also includes a decryption key generation unit that generates a decryption key based on the first distribution key and the second distribution key, and a decryption key generation unit that generates the decryption key based on the first distribution key and the second distribution key , and a decryption key generation unit that generates the decryption key based on the first distribution key and the second distribution key. The data processing apparatus may further include a decryption processing unit that decrypts the digital data string by applying permutation mapping using the decryption key.

The encryption device also includes a metadata extraction unit that extracts metadata from the acquired first data file, and a metadata extraction unit that adds the extracted metadata to the encrypted digital data string and adds the extracted metadata to the encrypted digital data string. The apparatus may further include a metadata adding section that generates the second data file.

Furthermore, the present invention according to another aspect may be a decryption device that decrypts a digital data string encrypted using an encryption key including at least one unit key consisting of n elements having a permutation relationship. . a decryption key generation unit that generates a decryption key corresponding to the encryption key; and a decryption key generation unit that generates a decryption key corresponding to the encryption key; a decryption processing unit that calculates at least one decryption array by applying permutation mapping using the decryption key, and a decrypted digital data string indicated by the calculated at least one decryption array; and an output control unit that performs control to output the second data file containing the data to the output destination. Here, the set of the decoding target array and the permutation mapping may be a group that satisfies the conditions of an associative law, the existence of an identity element, and the existence of an inverse element. Further, the permutation mapping converts the value of the i-th element of the decryption target array, which is indicated by the value Xi (i∈n) of the element of one of the unit keys in the decryption key, into the i-th element of the decryption array. It can be a binary operation that takes the value of the element of .

The decryption processing unit includes an area dividing unit that divides the encrypted digital data string to set a plurality of predetermined areas, and an element of a decryption target array corresponding to each of the plurality of predetermined areas. The method may include a calculation unit that calculates each of a plurality of decryption arrays by applying the permutation mapping to the value using the decryption key.

The area dividing unit may further divide each of the plurality of predetermined areas to set a new predetermined area. Further, the calculation unit applies the permutation mapping to the previously calculated element value of the encrypted array corresponding to the new predetermined area using the decryption key. A decoding array can be calculated.

Further, the decryption processing unit is configured to cause the area division unit to set a predetermined area and the calculation unit to calculate a decryption array corresponding to the encrypted digital data string to which N-fold encryption has been applied. may be configured to repeat.

Further, the decryption device includes a first distribution key acquisition unit that acquires a first distribution key based on the encryption key, and a user key that is based on a user key that includes at least one unit key consisting of n elements having a permuted relationship. The apparatus may further include a second distribution key acquisition unit that acquires a second distribution key. Here, the first distribution key may be an inverse mapping of the user key, and the second distribution key may be generated based on the encryption key and the inverse mapping of the user key. The decryption key generation unit may generate the decryption key based on the first distribution key and the second distribution key.

Furthermore, the present invention according to another aspect may be an encryption method for encrypting a digital data string to be encrypted, which is executed in a computer device. The method includes obtaining a first data file including the digital data string to be encrypted, and generating an encryption key including at least one unit key consisting of n elements having a permutation relationship. and applying permutation mapping to the element values of the encryption target array corresponding to at least one predetermined area constituting the digital data string that is the encryption target, using the generated encryption key. control to calculate at least one encrypted sequence and output a second data file containing an encrypted digital data string indicated by the calculated at least one encrypted sequence to an output destination. may include. Here, the set of the encryption target array and the permutation mapping is a group that satisfies the conditions of an associative law, the existence of an identity element, and the existence of an inverse element, and the permutation mapping is a group that satisfies the conditions of an associative law, the existence of an identity element, and the existence of an inverse element, It may be a binary operation that sets the value of the i-th element of the encryption target array, indicated by the element value Xi (iεn) of the unit key, to the value of the i-th element of the encryption array.

Furthermore, the present invention according to another aspect may be an encryption method for encrypting a digital data string to be encrypted, which is executed in a computer device. The method includes obtaining a first data file including the digital data string to be encrypted, and generating an encryption key including at least one unit key consisting of n elements having a permutation relationship. and applying permutation mapping to the element values of the encryption target array corresponding to at least one predetermined area constituting the digital data string that is the encryption target, using the generated encryption key. control to calculate at least one encrypted sequence and output a second data file containing an encrypted digital data string indicated by the calculated at least one encrypted sequence to an output destination. may include. Here, the set of the encryption target array and the permutation mapping is a group that satisfies the conditions of an associative law, the existence of an identity element, and the existence of an inverse element, and the permutation mapping is a group that satisfies the conditions of an associative law, the existence of an identity element, and the existence of an inverse element, It may be a binary operation that sets the value of the i-th element of the encryption target array, indicated by the element value Xi (iεn) of the unit key, to the value of the i-th element of the encryption array.

Furthermore, the present invention according to another aspect provides a method for decrypting a digital data string encrypted using a cryptographic key including at least one unit key consisting of n elements having a permutation relationship, executed in a computer device. It may be a decoding method for The first method includes the steps of: generating a decryption key corresponding to the encryption key; calculating at least one decryption array by applying permutation mapping using the generated decryption key; 2 data files to an output destination. Here, the set of the encryption target array and the permutation mapping is a group that satisfies the conditions of an associative law, the existence of an identity element, and the existence of an inverse element, and the permutation mapping is a group that satisfies the conditions of an associative law, the existence of an identity element, and the existence of an inverse element, It may be a binary operation that sets the value of the i-th element of the encryption target array, indicated by the element value Xi (iεn) of the unit key, to the value of the i-th element of the encryption array.

Furthermore, the present invention according to another aspect may be a computer program that causes a computing device to implement an encryption method for encrypting a digital data string to be encrypted, or a recording medium on which the program is recorded. The encryption method includes obtaining a first data file including the digital data string to be encrypted, and generating an encryption key including at least one unit key consisting of n elements having a permutation relationship. and applying a permutation mapping to the element values of the encryption target array corresponding to at least one predetermined area constituting the digital data string that is the encryption target, using the generated encryption key. control for calculating at least one encrypted sequence and outputting a second data file containing an encrypted digital data string indicated by the calculated at least one encrypted sequence to an output destination. This may include performing. Here, the set of the encryption target array and the permutation mapping is a group that satisfies the conditions of an associative law, the existence of an identity element, and the existence of an inverse element, and the permutation mapping is a group that satisfies the conditions of an associative law, the existence of an identity element, and the existence of an inverse element, It may be a binary operation that sets the value of the i-th element of the encryption target array, indicated by the element value Xi (iεn) of the unit key, to the value of the i-th element of the encryption array.

A computer that realizes a decryption method for decrypting a digital data string encrypted using an encryption key including at least one unit key consisting of n elements having a permuted relationship, which is executed in a computer device. It may be a program or a recording medium on which the program is recorded. The decryption method includes the steps of: generating a decryption key corresponding to the encryption key; and decoding element values of an array to be decrypted corresponding to at least one predetermined area constituting the encrypted digital data string. , calculating at least one decryption array by applying permutation mapping using the generated decryption key, and decrypting a decrypted digital data string indicated by the calculated at least one decryption array. The method may include controlling to output the second data file containing the second data file to the output destination. Here, the set of the encryption target array and the permutation mapping is a group that satisfies the conditions of an associative law, the existence of an identity element, and the existence of an inverse element, and the permutation mapping is a group that satisfies the conditions of an associative law, the existence of an identity element, and the existence of an inverse element, It may be a binary operation that sets the value of the i-th element of the encryption target array, indicated by the element value Xi (iεn) of the unit key, to the value of the i-th element of the encryption array.

Note that in this specification and the like, "means" (or "unit") does not simply mean physical means, but also includes cases in which the functions of the means are realized by software. Further, the function of one means may be realized by two or more physical means, or the functions of two or more means may be realized by one physical means.

According to the present invention, an encryption/decryption technique is provided that can perform robust and high-speed encryption/decryption processing of digital data while keeping the calculation load low.

Further, according to the present invention, encryption/decryption processing suitable for performing calculations on a GPU is provided.

Further, according to the present invention, a technique is provided that can encrypt digital data without changing the file format of the digital data.

Other technical features, objects, and effects or advantages of the present invention will be made clear by the following embodiments described with reference to the accompanying drawings.

1 is a block diagram for explaining an example of a computer system according to an embodiment of the present invention. 1 is a block diagram showing an example of the configuration of a content management device according to an embodiment of the present invention. FIG. 2 is a conceptual diagram for explaining divided areas in which digital data used in a system according to an embodiment of the present invention is divided into predetermined areas. FIG. 2 is a conceptual diagram for explaining encryption processing by a content management device according to an embodiment of the present invention. FIG. 2 is a conceptual diagram for explaining encryption processing by a content management device according to an embodiment of the present invention. FIG. 3 is a conceptual diagram for explaining an enlarged area based on divided areas of digital data used in a system according to an embodiment of the present invention. FIG. 2 is a conceptual diagram for explaining encryption processing by a content management device according to an embodiment of the present invention. 3 is a flowchart illustrating an example of encryption processing in a content management device according to an embodiment of the present invention. 1 is a block diagram showing an example of the configuration of a client in a system according to an embodiment of the present invention. FIG. 2 is a conceptual diagram for explaining an encryption key and a decryption key in a system according to an embodiment of the present invention. FIG. 3 is a conceptual diagram for explaining decryption processing by a client according to an embodiment of the present invention. 3 is a flowchart illustrating an example of decryption processing in a client according to an embodiment of the present invention. FIG. 3 is a diagram illustrating an example of an original image in a predetermined file format. 12A is a diagram showing an example of an encrypted image obtained by applying the encryption technique according to the present invention to the original image shown in FIG. 12A. FIG. 12B is a diagram showing an example of a decrypted image (original image) obtained by applying the decryption technique according to the present invention to the encrypted image shown in FIG. 12B. FIG. FIG. 3 is a diagram showing an example of an encryption key and a user key in the encryption/decryption technology according to the present invention. 1 is a diagram illustrating an example of a configuration of a computing device in a system according to an embodiment of the present invention.

Embodiments of the present invention will be described below with reference to the drawings. However, the embodiments described below are merely examples, and there is no intention to exclude the application of various modifications and techniques not specified below. The present invention can be implemented in various ways (for example, by combining the embodiments) without departing from the spirit thereof. In addition, in the description of the drawings below, the same or similar parts are denoted by the same or similar symbols. The drawings are schematic and do not necessarily correspond to actual dimensions or proportions. The drawings may also include portions that differ in dimensional relationships and ratios.

[First embodiment]
This embodiment discloses a technique for encrypting and decoding a digital data string as digital content, which is composed of a multiple array of finite elements, using the concept of "permutation mapping group." Below, the permutation mapping group will be explained first, and then an example of an encryption/decryption device using the permutation mapping group will be explained.

(group)
When a set of an arbitrary set G and a binary operator μ on the set G satisfies a certain condition, the set (G, μ) is called a group. In other words, (G, μ), where μ: G×G → G, is a group under three conditions: (1) associative law, (2) existence of identity element, and (3) Existence is fulfillment. Note that the set G can also be called a group with respect to the binary operator μ.

(Associative law)
For elements g, h, k of any set G, μ(g, μ(h, k)) = μ(μ(g, h), k):
(∀g, h, k, ∈G) [μ(g, μ(h, k)) = μ(μ(g, h), k)] …Equation 1

(Existence of identity element)
For any element g, there exists an element e∈G that satisfies μ(g, e) = μ(e, g) = g:
(∃e∈G) (∀g∈G) [μ(g,e)=μ(e,g)=g] …Formula 2

(Existence of inverse element)
For any element g∈G, there exists an element x∈G that satisfies μ(g,x) = μ(x,g):
(∀g∈G) (∃x∈G) [μ(g,x)=μ(x,g)=e] …Formula 3

(n-permutation mapping group)
Let n∈N. Here, N is a set of integers greater than or equal to 0 and less than or equal to n. A sequence in which the elements xi of the set N are mutually exclusive is called an n-permutation. Now, for g which is an n-permutation, g=[x0, x1, . ．． ．． , xn]|xi≠xj, xi∈N, and let the set of permutations be g∈G. At this time, the number of permutation sets is |G|=n! becomes. For example, taking the permutation (3-permutation) when n = 3, the set G is the permutation [0, 1, 2], [0, 2, 1], [1, 0, 2], [ 1, 2, 0], [2, 0, 1], and [2, 1, 0], and the order (number of elements in the set) is 6.

Mapping generally refers to making each element of a set correspond to each other element. In this disclosure, let G be a set based on n-permutations, and for arbitrary elements g1 and g2, extract the value (Xi) indicated by the i-th (i∈n) element of g2, and By applying the mapping μ that moves the value of the th element to the value of the i-th element, the element g3 is referred to as an n-permutation mapping group (G, μ). Below, for 4-permutations, the elements g = [1, 2, 0, 3], h = [3, 0, 1, 2], k = [2, 0, 3, 1] of the permutation set G are used as an example. Next, consider three conditions for groups.

From Equation 1 above, μ(g, μ(h, k)) = μ(g, [1,3,2,0]) = [2,3,0,1], while μ(μ(g ,h),k)=μ([3,1,2,0],k)=[2,3,0,1]. Therefore, (G, μ) satisfies the associative law.

From Equation 2 above, for e=[0,1,2,3], μ(g,e)=[1,2,0,3]=g, and μ(e,g)=[1 ,2,0,3]=g. The element e is an identity element because it holds true for any element, not just the element g. Therefore, (G, μ) has an identity element.

From Equation 3 above, x=[2,0,1,3] is μ(g,x)=[0,1,2,3]=e, and μ(x,g)=[0 , 1, 2, 3] = e, so x is the inverse of g. Therefore, (G, μ) has an inverse element.

The n-permutation mapping group is generally non-commutative, ie, μ(g,h)≠μ(h,g). In the above example, μ(g, h) = [3, 1, 2, 0], but μ(h, g) = “0, 1, 3, 2], which is non-commutative. It has become.

(Basic concept of encryption/decryption using n-permutation mapping)
Consider encrypting and decrypting a certain iεN=[0, n] using these permutation mappings. As mentioned above, the n-permutation mapping is a mapping of the operator f(i) using the n-permutation f to return the i-th value of the n-permutation f (below, the n-permutation mapping is simply referred to as (Also called "permutation mapping" or "mapping.") For example, by applying an n-permutation mapping f(x) to a value x to be encrypted, an encrypted value y can be obtained. This is expressed as y=f(x). Furthermore, by applying an inverse mapping f ⁻¹ (y) using the inverse element f ⁻¹ of f to y, it is possible to decode it to the original value x. That is, x=f ⁻¹ (y).

For example, for the element g = [1, 2, 0, 3] of the permutation set G mentioned above, in the case of encryption, the mapping g(2) means returning the value of the second element of the element g. Therefore, g(2)=0, and therefore "2" is encrypted to "0". On the other hand, in the case of decoding, the inverse element of element g, that is, g ⁻¹ = [2,0,1,3] is used. In other words, since the inverse mapping g ⁻¹ (0) means returning the value of the 0th element of g ⁻¹ , g ⁻¹ (0)=2, which means that the decoding is correct.

The above can be extended not only to single numbers but also to sequences of numbers. For example, a numerical sequence to be encrypted is expressed as X={x1, x2, . . . , xm}, x∈N. Then, consider a mapping F(X) where F:X→X, in which mapping f(x) is applied to all elements of the sequence X.

That is, first, F(X)={f(x1), f(x2), . . . , f(xm)} is generated. By using such a mapping F(X), it is possible to encrypt the original number sequence. In this sense, the mapping can be called an encryption mapping or an encryption key.

On the other hand, consider the inverse mapping F ^{-1 (X) in which the inverse mapping f -1 (} x) using the inverse element f ^-1 of the permutation f is applied to all elements of the sequence X. At this time, the inverse mapping F ^-1 (X) becomes F ^-1 = {f ^-1 (x1), f ^-1 (x2), ..., f ^-1 (xm)}.

More specifically, for example, when applying the mapping G(X) of the permutation set G to the sequence X = {3, 3, 2, 0, 1}, G(X) = {g(3), g( 3), g(2), g(0), g(1)}={3,3,0,1,2}=Y. For this result, the inverse mapping G ^-1 (Y) is G ^-1 (Y)={g ^-1 (3), g ^-1 (3), g ^-1 (0), g ^-1 (1 ), g ⁻¹ (2)}={3, 3, 2, 0, 1}, which means that it was decoded correctly.

(Encryption and decryption of multidimensional array)
The above idea is further extended to multiple arrays XεN ⁿ . In the present disclosure, for ease of understanding, encryption using ^a two-dimensional array /decryption will be described, but the encryption/decryption technology according to the present disclosure can be applied to n-dimensional arrays, but is not limited thereto.

Now, assume that the element at the i-th row and the j-th column of the array X is x _ij . At this time, similar to the encryption of the number sequence mentioned above,
y _ij =f(x _ij )...Formula 4
By doing so, the array X can be encrypted.

とする。これに、Ｆ＝［２，０，１］を配列Ｘに作用させた写像Ｆ（Ｘ）は、

となる。 For example, array X is

shall be. The mapping F(X) by applying F=[2,0,1] to the array X is

becomes.

となる。 On the other hand, the inverse mapping F ^-1 (Y) that applies F ^-1 = [1, 2, 0] to the array Y is

becomes.

であり、その要素をｆ_ｉｊ（ｘ_ｉｊ）と定義する。ｆ_ｉｊは、一次元の順列写像であり、したがって、Ｆ（Ｘ）は、３階のテンソルとなる。すなわち、
ｙ_ｉｊ＝ｆ_ｉｊ（ｘ_ｉｊ） …式８
となる。このようにすることで、暗号化及び復号化がより複雑化される。 (Multidimensional mapping)
As mentioned above, by using the n-permutation mapping, it is possible to encrypt a certain array (for example, a digital data string representing a rasterized image) X to obtain the array Y, and by using the inverse mapping, , the encrypted array Y can be decrypted to obtain the original array X. In the present disclosure, in order to make encryption more complex and raise the security level, a multidimensional mapping F(X) is considered that has different mappings for different arrays. here,

, and its element is defined as f _ij (x _ij ). f _ij is a one-dimensional permutation map, and therefore F(X) is a third-order tensor. That is,
y _ij = f _ij (x _ij ) ...Formula 8
becomes. By doing so, encryption and decryption become more complicated.

に対して、

を配列Ｘに適用した写像は、

となる。 For example, consider the case where w=h=2 and n=3.

For,

The mapping that is applied to the array X is

becomes.

を配列Ｙに適用した逆写像は、

となる。 Conversely,

The inverse mapping applied to the array Y is

becomes.

Note that when the mapping is applied to a more generalized multiple array X∈N ⁿ , F∈N ⁿ⁺¹ , F:X→X.

(Reduction of mapping)
The size of a tensor element of a mapping for an image (width w x height h) that is a two-dimensional array is w x h x n. For example, when encrypting an image of 1024×1024 pixels and 8-bit gradation, the size of the uncompressed data reaches 256 MB, and a very large size array is required to handle this. Therefore, in order to reduce the array size, a reduced mapping is introduced. In this disclosure, the reduced mapping is referred to as a "kernel" (distinguished from the OS kernel), and in particular, the kernel in the encryption mapping is referred to as the "encryption mapping kernel K", and the kernel in the decryption mapping is referred to as the "encryption mapping kernel K". shall be referred to as "decoding mapping kernel K ^-1 ".

That is, if the width of the kernel is k _w and the height is k _h , then the size of the tensor element is k _w × _kh ×n. For example, if k _w =k _h =64 and n=256, the array size will be 64 x 64 x 256 = approximately 1 MB.

Therefore, by dividing the image to be encrypted into regions or segments of a predetermined size and applying a kernel of a size corresponding to each of the divided regions, the array size can be reduced and the memory Consumption can be reduced.

(Schematic system configuration)
Next, a system for implementing encryption and decryption using the above-mentioned n-permutation mapping will be described.
FIG. 1 is a block diagram for explaining an example of a computer system according to an embodiment of the present invention. As shown in the figure, the computer system 1 of the present disclosure may be configured to include, for example, a content management device 20 and a client 30 that are communicably connected to each other via a communication network 10.

The communication network 10 includes, for example, an IP-based computer network. In this disclosure, the computer network is used as a broad concept including the Internet constructed by IP networks ("the Internet"), but is not limited to IP networks, and can include any network using any protocol that enables communication between nodes. Applicable. Therefore, the communication network 10 may include a wireless network established by a wireless base station (eg, Wi-Fi (registered trademark)) not shown. Furthermore, the communication network 10 may include a mobile communication network compliant with mobile communication system standards.

The content management device 20 is a server system for appropriately managing data files as digital content, and may include, for example, a database 22 and a server 24. The content management device 20 may be, for example, a web server that configures a website or a cloud server that provides cloud services. Server 24 and database 22 may each be built on separate computing devices, or each may be built on one physically or logically one computing device. The hardware configuration of such a computing device is illustrated in FIG. 14, but since it is known, detailed description thereof will be omitted. Note that in the figure, the processor module may include various processors such as a CPU, a core processor, a coprocessor, and/or a GPU. The content management device 20 can establish a secure communication session with the client 30 and other external devices via the communication network 10, for example, by using a secure communication technology such as SSL.

In the present disclosure, the content management device 20 is an encryption and/or decryption device (hereinafter referred to as "encryption/decryption device", simply "encryption device" and " It can function as a "decoding device". In other words, the processor (processor module) of the content management device 20 has an encryption and/or decryption program (hereinafter referred to as "encryption/decryption program", simply referred to as "encryption program" and "decryption program"). ), the content management device 20 is made to function as an encryption/decryption device.

In this disclosure, an example will be described in which the content management device 20 encrypts digital data related to rasterized images and videos, and decrypts the encrypted digital data. In particular, since the content management device 20 can perform encryption and decryption processing using its pixel shader and compute shader under the control of the GPU, the processing speed is increased.

The database 22 can store various digital contents (digital data) such as documents, comics, illustrations, photographs, moving images, or videos as data files in a predetermined file format. In the present disclosure, the file format of digital content is not particularly limited, and any known file format can be used. The data file of the digital content may be stored in the database 22 in an encrypted state using the encryption technology according to the present disclosure. Further, the database 22 can manage, for example, user information (user accounts and passwords) regarding users who use digital content. Further, the database 22 can manage, for example, a predetermined encryption key and/or decryption key (distribution key) for each user to use each digital content.

Server 24 may provide digital content stored in database 22 and/or predetermined distribution keys in response to requests from authorized users. A legitimate user is typically a user who has been given the right to use predetermined digital content by the operating entity of the content management device 20, and, for example, has undergone a formal user registration procedure, and furthermore, This may be a user who has paid a considerable amount of money.

Client 30 is typically a computing device used by a user. Client 30 can be, for example, a personal computer such as a desktop computer or notebook computer, a tablet computer, a feature phone, a smart phone, a PDA, a handheld computer, and other intelligent devices. In this disclosure, it is assumed that the client 30 is a personal computer.

That is, the client 30 includes hardware such as various processors (e.g., CPU, core processor, coprocessor, and/or GPU, etc.), chipsets and memories, communication modules, user interfaces (e.g., display or touch panel, speakers, and vibrators). It is composed of software resources of a software resource and an operating system (for example, it may include a kernel, various device drivers, standard libraries, etc.; hereinafter referred to as "OS"). The client 30 executes various application programs on the OS under the control of the processor to achieve desired functions. In the present disclosure, the client 30 implements an application program (hereinafter referred to as "decryption program") for decrypting encrypted digital data as one of the application programs. Alternatively or additionally, client 30 may implement a web browser program, for example. The decryption program may be implemented as a plug-in program for a web browser program. In particular, the client 30 can perform the decoding process with its pixel shader under the control of the GPU, thereby speeding up the process.

In the present disclosure, assuming a general usage mode of digital content distribution, the content management device 20 encrypts and decrypts digital content, and the user's client 30 only performs decryption. described, but not limited to. For example, an encryption/decryption program may be implemented in the user's client 30, and the client 30 may also be configured to perform encryption.

(Description of encryption device)
FIG. 2 is a block diagram showing an example of the configuration of a content management device in a system according to an embodiment of the present invention. In the figure, among the various components of the content management device 20 that functions as an encryption device, components related to the present disclosure are shown, but as far as it is obvious to a person skilled in the art, they are not shown. Other components may also be included. That is, as shown in the figure, the content management device 20 includes a digital content acquisition unit 210, a metadata extraction unit 220, a key generation unit 230, an encryption processing unit 240, a metadata addition unit 250, and an output The control unit 260 may be configured to include a control unit 260. As will be obvious to those skilled in the art, such a component may be a hardware component itself or, for example, a processor of the server 24 may cooperate with various hardware resources by executing an encryption program on the OS. It can be realized.

The digital content acquisition unit 210 acquires digital content to be encrypted from the database 22, for example. Alternatively, the digital content acquisition unit 210 may acquire digital content uploaded from the client 30. As an example, the digital content is a data file of a rasterized image (for example, 320 x 280 pixels, 8-bit gradation image), but is not limited to this, and may be any digital data string related to certain information. . For example, the digital content may be a moving image data file or a music data file. Additionally, digital content may be document data. Further, it may be a data file in the DiCOM format used in medical imaging devices and the like. As another example, digital content may be streaming data. In the following, it is assumed that the digital content to be encrypted is rasterized image data of 320×280 pixels and 8-bit gradation. The digital content acquisition unit 210 outputs the acquired digital content to the metadata extraction unit 220. Note that in this disclosure, the expression "output data" does not literally mean outputting data to an output destination on a system or program, but also means, for example, directly assigning data to a predetermined variable or using a pointer. It includes the meaning of handing over something and should not be interpreted in a limited manner.

The metadata extraction unit 220 inspects the acquired digital content, and if the digital content includes predetermined metadata, extracts and separates the metadata from the digital content. The metadata extracting unit 220 outputs the extracted metadata to the metadata adding unit 250, while encrypting the digital content body (hereinafter simply referred to as “digital content” unless there is a need to distinguish). 240. For example, in the case of digital content in the JPEG file format, the metadata extraction unit 220 extracts and separates data written in the Exif format as metadata. As another example, if the metadata extraction unit 220 cannot recognize a predetermined file format for the digital content, the metadata extraction unit 220 outputs the entire digital content to the encryption processing unit 240, and the metadata addition unit 250 includes null data. Output.

The key generation unit 230 generates various keys necessary to implement encryption/decryption processing according to the present disclosure. Roughly speaking, the key generation unit 230 generates an encryption key F and a user key U, respectively, based on a predetermined key generation algorithm (for example, a random number function based on a seed). In this disclosure, the cryptographic key F is formed as a cryptographic mapping kernel K. The user key U is a key assigned to each user who wishes to use digital content to be encrypted. Furthermore, the key generation unit 230 generates an auxiliary key V based on the encryption key F and the user key U. That is, the auxiliary key V is a key associated with the user key U. Further, the user key U and the auxiliary key V are keys to be distributed to users. As an example, the key generation unit 230 generates a first distribution key D1 based on the user key U, and generates a second distribution key D2 based on the auxiliary key V. Details of the key generation unit 230 will be described later.

The encryption processing unit 240 encrypts the digital content based on the encryption mapping kernel K generated by the key generation unit 230. Generally speaking, the encryption processing unit 240 first divides the digital content into regions or segments of a predetermined size, and then applies an encryption mapping kernel to an array indicating the divided regions (hereinafter referred to as "divided regions"). By applying K, an encrypted sequence is calculated. Furthermore, when multiple encryption is applied, the encryption processing unit 240 sets an enlarged area based on a plurality of adjacent divided areas, applies the encryption mapping kernel K to the array indicating the enlarged area, and encrypts the area. Repeat the process of calculating the array. In the present disclosure, the enlarged region is set based on a plurality of adjacent divided regions; however, the enlarged region is not limited to this, and for example, the enlarged region is set based on a predetermined geometric pattern (for example, a checkered pattern). May be set. The encryption processing unit 240 outputs the calculated encryption sequence to the metadata adding unit 250. Details of the encryption processing unit 240 will be described later.

The metadata adding unit 250 restores the original file format by adding the metadata extracted by the metadata extracting unit 220 to the calculated encrypted sequence. The metadata adding unit 250 outputs the data set of the encrypted array of the restored file format to the output control unit 260. When Null data is provided from the metadata extraction unit 220, the metadata addition unit 250 outputs the encrypted array data set received from the encryption processing unit 240 as is to the output control unit 260.

The output control unit 260 outputs the various data sets received to any corresponding output destination. For example, upon receiving the data set of the calculated encrypted sequence, the output control unit 260 controls the data set to be stored in the database 22 as an encrypted digital content data file. Further, for example, the output control unit 260 performs control so that the user key and the auxiliary key are stored in the database 22 in association with the user and the digital content, respectively. Further, for example, the output control unit 260 performs control to transmit the first distribution key and the second distribution key to the client 30.

Here, details of the key generation unit 230 will be explained. As shown in the figure, the key generation section 230 may include, for example, an encryption key generation section 2310, a user key generation section 2320, and an auxiliary key generation section 2330. Further, the key generation section 230 may include a first distribution key generation section 2340 and a second distribution key generation section 2350.

As described above, the encryption key generation unit 2310 generates the encryption key F for encrypting digital content. The encryption key F is a collection of a plurality of unit keys, and each encryption key F is, for example, a numerical sequence in which each of the numbers from 0 to 255 is exclusively arranged (that is, the permutation f=[f0, f1,... , f255]). In other words, it can be said that the element values f0, f1, ..., f255 are in a permutation relationship. The encryption key generation unit 2310 generates such a number sequence using, for example, a random number function based on a predetermined seed. The number of elements in the permutation related to the encryption key F corresponds to the 8-bit tone value of the pixel. Furthermore, the number of encryption keys F corresponds to the number of elements (that is, pixels) within the divided areas of the digital content, as will be described later. For example, when digital content is divided into areas of 64x64 pixels, the number of encryption keys F is 64x64. Such a cryptographic key F is a cryptographic mapping kernel K used for array size reduction. The encryption mapping kernel K can also be regarded as a 3D texture in which a plurality of permutations are arranged. In the present disclosure, for example, only one encryption mapping kernel K is generated for the data file of the digital content to be encrypted, but the invention is not limited to this. For this, one cryptographic mapping kernel K may be assigned. The encryption key generation unit 2310 outputs the generated encryption key F (that is, the encryption mapping kernel K) to the encryption processing unit 240 and the auxiliary key generation unit 2330, respectively.

The user key generation unit 2320 generates a user key U to be assigned to each user who wants to use digital content. The user key generation unit 2320 can generate a user key U for each user, for example, according to user information stored in the database 22. The user key U is also a collection of a plurality of unit keys, and each unit key is, for example, a numerical sequence in which each of the numbers from 0 to 255 is exclusively arranged (i.e., permutation u=[u0, u1,... , u255]). The user key generation unit 2320 generates such a number sequence using, for example, a random number function based on a predetermined seed. The number of elements in the permutation corresponds to the 8-bit tone value of the pixel. Further, the number of unit keys constituting the user key U corresponds to the number of elements within the divided area. The user key U is a key corresponding to the encryption key F, but is a key that is generated independently (irrelevantly). User key generation section 2320 outputs the generated user key U to auxiliary key generation section 2330 and first distributed key generation section 2340, respectively. In the present disclosure, a different user key U is generated for each user. However, the present disclosure is not limited to this, and the user key U may be assigned to each user group consisting of a plurality of users, for example. good.

The first distribution key generation unit 2340 generates a first distribution key D1 based on the generated user key U. Specifically, the first distribution key generation unit 2340 calculates the inverse mapping key U ^-1 of the generated user key U, and sets this as the first distribution key D1. The first distribution key generation section 2340 outputs the generated first distribution key D1 to the auxiliary key generation section 2330 and the output control section 260. Note that although in this example, the first distribution key generation section 2340 is provided in the content management device 20, the first distribution key generation section 2340 may be provided in the client 30. In this case, the user key generation unit 2320 can calculate the inverse mapping key U ⁻¹ of the generated user key U instead of the first distributed key generation unit 2340.

The auxiliary key generation unit 2330 generates an auxiliary key V based on the encryption key F and the user key U (inverse mapping U ⁻¹ ). For example, the encryption key generation unit 2310 generates the auxiliary key V by performing a binary operation on the encryption key F and the inverse mapping key U ^-1 . More specifically, the encryption key generation unit 2310 applies a permutation mapping to the inverse mapping U ⁻¹ using the encryption key F to generate an auxiliary key F (V=U ⁻¹・F). do. Therefore, the auxiliary key V is also a collection of numerical sequences in which each of the numbers from 0 to 255 is exclusively arranged (ie, permutation v=[v0, v1, . . . , v255]).

The second distribution key generation unit 230 generates a second distribution key D2 based on the generated auxiliary key V. Specifically, the second distribution key generation unit 230 calculates the inverse mapping key V ^-1 of the generated auxiliary key V, and sets this as the second distribution key D2. The second distribution key generation unit 230 outputs the generated second distribution key D2 to the output control unit 260. Note that although in this example, the second distribution key generation section 230 is provided in the content management device 20, the second distribution key generation section 230 may be provided in the client 30.

Next, details of the encryption processing section 240 will be explained. As shown in the figure, the encryption processing unit 240 may include, for example, an area dividing unit 2410, a calculation unit 2420, and an enlarged area setting unit 2430.

The area dividing unit 2410 divides the acquired digital content into areas of a predetermined size, for example, an area of width w×height h, as shown in FIG. That is, for example, if the digital content is a 320×280 pixel image, the region dividing unit 2410 divides it into 64×64 pixel regions. This is to reduce the size of the array of the encryption mapping kernel K by reducing the size of the data to be encrypted. For example, the size of an (uncompressed) image with 320 x 280 pixels and 8-bit gradation value is approximately 90 KB (=320 x 280 x 8/8), and if the number of array elements n = 256, then The size of the file is approximately 22.9MB. On the other hand, in the case of an image of a divided area, the number of array elements n=256, and the size of the array is approximately 1 MB (=64×64×256). This difference becomes more noticeable when the image size is large and/or when the image is a color image (RGB 24 bits). Note that, for example, in the case of an image of 320×280 pixels, if the image is divided into 64×64 pixels, a remainder will occur in the height direction. In this case, the number of divisions in the height direction is the smallest integer value larger than the quotient, and pixels in the portion exceeding the original size are assigned "0" by zero padding. The region dividing section 2410 outputs data blocks (array data) for each divided region to the calculating section 2420.

The calculation unit 2420 applies the encryption mapping kernel K to each pixel value (gradation value) in the divided area to calculate an encryption array. That is, as shown in Equation 6, the calculation unit 2420 applies permutation mapping F(X) of permutation f as encryption mapping kernel K to each of all elements (pixels) of array X indicating the divided area. Then, array Y is calculated.

Note that when multiple encryption is applied, the encryption processing unit 240 repeats application of permutation mapping F(X) a predetermined number of times while expanding the area, and applies the finally calculated array Y to multiple encryption. It is output to the metadata adding section 250 as an array Z. In this way, the encryption processing unit 240 repeats application of the permutation mapping F(X) a predetermined number of times while expanding the area, so even if the values of adjacent elements are the same, the feature is erased. Therefore, it becomes difficult for third parties to understand decryption hints.

For ease of understanding, an example in which a 3-permutation mapping is applied to a 2×2 pixel divided area will be described using FIGS. 4A and 4B.

As shown in FIG. 4A(a), it is assumed that there is an array X indicating the value of each pixel in a 2×2 pixel divided area in a certain image and an encrypted mapping kernel K. Further, in the figure, the numbers starting with # of the encryption mapping kernel K indicate the numbers of the elements of the encryption mapping kernel K.

The calculation unit 2420 first focuses on the first element of the array X, that is, "0" at the upper left. The corresponding encryption key at this time is the upper left permutation of the encryption mapping kernel K (indicated by hatching in the figure; the same applies hereinafter). According to the value "0" of this element, the calculation unit 2420 sets the 0th element in the encryption mapping kernel K as the element to be referred to ((i) in the figure), and sets the value "0" of that element to the correspondence of the array Y. ((ii) in the figure).

Subsequently, as shown in FIG. 4A(b), the calculation unit 2420 focuses on the next element of the array X, that is, "2" at the upper right. The corresponding encryption key at this time is the upper right permutation of the encryption mapping kernel K. According to the value "2" of this element, the calculation unit 2420 sets the second element in the encryption key as the element to be referred to ((i) in the figure), and sets the value "2" of the element to the corresponding element of the array Y. Set to the value ((ii) in the figure).

Subsequently, as shown in FIG. 4B(a), the calculation unit 2420 focuses on the next element of the array X, that is, "1" at the lower left. Similarly, according to the value "1" of this element, the calculation unit 2420 sets the value "0" of the first element in the corresponding encryption key as the element to be referred to ((i) in the figure) in the array Y. Set to the value of the corresponding element ((ii) in the figure).

Similarly, as shown in FIG. 4B(b), the calculation unit 2420 selects the 0th element in the corresponding encryption key as the element to be referenced (( i)), the value "2" of that element is set to the value of the corresponding element of array Y ((ii) in the figure).

As described above, the calculation unit 2420 applies the corresponding encryption keys in the encryption mapping kernel K to the array X indicating the value (gradation value) of each pixel in the divided area, and Calculate. When multiple encryption is applied to the calculated array Y, permutation mapping F(X) is repeatedly applied as described later, and thereby the array Y finally becomes a multiple encryption array Y.

Returning to FIG. 2, the enlarged area setting unit 2430 sets an enlarged area (hereinafter referred to as "enlarged area") including adjacent divided areas corresponding to the encrypted array. For example, as shown in FIG. 5, the enlarged area is a 2x2 block area in which one block is an array of divided areas of 64x64 pixels. Similarly, pixels in the remainder of the enlarged area are assigned "0" by zero padding. The enlarged area setting unit 2430 outputs an array (hereinafter referred to as “enlarged array”) corresponding to the set enlarged area to the calculation unit 2420.

When the arithmetic unit 2420 receives the enlarged array from the enlarged area setting unit 2430, it applies the permutation mapping F(Y) to all elements in the array Y of the enlarged area, as shown in Equation 6, and performs superposition in a superimposed manner. Calculate the encrypted array Z.

For ease of understanding, an example in which the encryption mapping kernel K is applied to the array of enlarged regions will be described with reference to FIG. 6, based on the examples shown in FIGS. 4A and 4B .

As shown in FIG. 6, consider four arrays X corresponding to four divided areas of 2×2 pixels in a certain image. As described above, the calculation unit 2420 applies each encryption key F in the encryption mapping kernel K to each of the arrays X, and calculates the four encryption arrays Y.

Next, the expansion area setting unit 2430 creates a 2×2 block expansion area using each of the four encrypted arrays Y as a block. Subsequently, the calculation unit 2420 calculates the encrypted array Z by applying the mapping using the encryption key to all the elements in each block.

More specifically, the calculation unit 2420 first focuses on the upper left element "0" in the upper left array X. Since element "0" is located at the upper left of the upper left array X, the upper left permutation of the kernel is used as the encryption key. The calculation unit 2420 sets the 0th element "0" in the corresponding encryption key to the value of the element at the corresponding position in the array Y according to the value "0" of this element. Similarly, the calculation unit 2420 calculates the second upper right element "2" in the encryption key for the upper right element "2" in the upper left array X, and the lower left element " 1 " in the upper left array X. , the 0th lower left element "0" in the encryption key, and the lower right element " 0 " in the upper left array X , the 0th lower right element "2" in the encryption key, respectively. Set to the value of the element at the corresponding position in Y.

Similarly, regarding the upper right array X , the calculation unit 2420 sets the 0th element "1" in the upper right encryption key to the value of the corresponding element in the array Y for the upper left element "0" . Similarly, the calculation unit 2420 applies mapping using the corresponding encryption keys to the lower left and lower right arrays X.

Similarly, the calculation unit 2420 applies mapping using the encryption key corresponding to the position of the array Y to all elements in each array Y. In this example, the values of the elements in the upper right array Z are all the same because the values of the elements in the upper right array Y are all the same. Then, the calculation unit 2420 performs the above processing on all enlarged areas in the digital content to be encrypted.

FIG. 7 is a flowchart illustrating an example of encryption processing in the content management device according to an embodiment of the present invention. Such processing is realized, for example, by the content management device 20 executing an encryption program under the control of a processor (processor module). Note that such processing may be performed sequentially, or may be performed in parallel or in parallel as long as there is no inconsistency in the results of the processing. In the following, digital content will be explained as image data.

As shown in the figure, the content management device 20 acquires digital content to be encrypted from, for example, the database 22 (S701). Alternatively, the content management device 20 may obtain digital content uploaded from the client 30.

Next, the content management device 20 extracts metadata from the acquired digital content, and extracts the metadata and the digital content itself (S702). Extracted metadata is temporarily retained in memory and/or work files.

Next, the content management device 20 divides the digital content body into regions of a predetermined size, for example, regions of width k _w ×height k _h (S703). As mentioned above, for example, if the original digital content is a 320x280 pixel image, the image is divided into 64x64 pixel regions. Note that if the size of the original image is not an integral multiple of the size of the divided area, the size of the original image is changed so that the size of the original image can be treated as an integral multiple of the size of the divided area. The portion exceeding the limit is zero padded.

Next, the content management device 20 sets a counter COUNT (where COUNT≦N) to “1” in order to perform N-fold encryption (S704). Note that in this example, N=2. Subsequently, the content management device 20 generates an encryption mapping kernel K based on the encryption key for each pixel in the divided area (S705). For example, each cryptographic key consists of an exclusively randomly ordered sequence of numbers from 0 to 255 (i.e., permutation f=[f0, f1,... , f255]).

Next, the content management device 20 applies permutation mapping using the corresponding encryption key to the value of each element (i.e., pixel) in the divided area, as shown in Equation 6, and calculates an encryption array. (S706). The content management device 20 applies permutation mapping using the encryption mapping kernel K to all divided areas.

After applying the permutation mapping by the encryption mapping kernel K, the content management device 20 increments the value of the counter COUNT by one (S707), and determines whether the N-fold encryption is completed (S708). In this example, since the value of the counter COUNT does not exceed N=2 (No in S708), the content management device 20 stores each of the arrays of encrypted divided areas in order to perform the second encryption. The enlarged area made into an element is set (S709), and the process returns to S706.

Then, the content management device 20 calculates an encrypted array by applying permutation mapping using the corresponding encryption key in the encrypted mapping kernel K to the enlarged array corresponding to each enlarged area (S706). Similarly, the content management device 20 increments the value of the counter by one (S707), and determines whether the N-fold encryption is completed (S708). In this case, since the value of the counter COUNT exceeds N=2, the N-fold encryption process ends (Yes in S708). Next, the content management device 20 reads the temporarily stored metadata and adds the metadata to all the calculated data based on the encrypted sequence (S710). The encrypted data is output as encrypted digital content (S711).

As described above, when the content management device 20 acquires digital data as digital content, it can encrypt it using the above-mentioned n-permutation mapping and output the encrypted digital content. The encryption technology according to the present disclosure performs encryption processing on the data body from which metadata has been extracted from digital content, and then adds the extracted metadata to the encrypted data. Even after the conversion process, the file format remains unchanged (maintains as is). Therefore, when the file format of digital content is, for example, PNG (Portable Network Graphics), the encrypted digital content can be interpreted by a PNG-compatible viewer, but the displayed image is This results in a snow noise (so-called sandstorm)-like image in which dots appear, and the original image cannot be recognized (see FIGS. 12A and 12B).

As described above, according to the encryption technology according to the present disclosure, the file format is not changed, so for example, by encrypting an image embedded by a link in an HTML script page, an HTML-based page can be created on the browser. It is now possible to display the image embedded therein, while displaying the embedded image in an unrecognizable state until it is decoded.

The content management device 20 can also function as a decryption device that performs decryption processing corresponding to encryption processing. The decoding process will be described below using the client 30 as an example.

(Description of decoding device)
FIG. 8 is a block diagram showing an example of the configuration of a client in a system according to an embodiment of the present invention. Of the various components of the client 30, those related to the present disclosure are shown in the figure, but other components not shown are also included as far as it is obvious to a person skilled in the art. obtain. That is, as shown in FIG. It may be configured to include a data provision section 360 and an output control section 370. As will be obvious to those skilled in the art, such components can be realized by the hardware components themselves, or by the processor of a server cooperating with various hardware resources, for example by executing an encryption program on the OS. can be done.

The digital content acquisition unit 310 acquires digital content encrypted according to the encryption technology according to the present disclosure from, for example, a file system on a storage device (not shown). Typically, prior to the decryption process, the encrypted digital content is downloaded from the content management device 20 via the communication network 10 and stored in the file system of the client 30. As an example, a user accesses the content management device 20 as a website using a web browser, receives predetermined user authentication, downloads encrypted digital content, and saves it in a file system.

The key acquisition unit 320 acquires a distributed key (hereinafter referred to as "distributed key") for decrypting encrypted digital content from, for example, a file system on a storage device (not shown). In the present disclosure, the distribution key is composed of, for example, a pair of a first distribution key and a second distribution key, and therefore, the key acquisition unit 320 includes a first distribution key acquisition unit 3210 and a second distribution key acquisition unit 3220. It may be configured to include. As described above, the first distribution key D1 is the inverse mapping U ^-1 of the user key U, and the second distribution key D2 is the inverse mapping V ^-1 of the auxiliary key V. Note that in a mode in which the user key U and the auxiliary key V are distributed to users as distribution keys as they are, the first distribution key acquisition unit 3210 and the second distribution key acquisition unit 3220 calculate the inverse origin of the received distribution key. By calculating each, a first distribution key D1 and a second distribution key D2 are obtained. For example, the distribution key acquisition unit 320 may acquire the first distribution key and the second distribution key simultaneously or separately. Typically, prior to the decryption process, the distribution key is downloaded from the content management device 20 via the communication network 10 and stored in the file system of the client 30. For example, a user accesses the content management device 20 as a website via a web browser, receives predetermined user authentication, downloads the distribution key, and saves it in the file system. Alternatively, the user receives an email containing an attached file with an archived decryption key via a mailer, and saves the attached file in the file system. Alternatively, the distribution key may be distributed to users, for example by a USB memory device or dongle.

The metadata extraction unit 330 inspects the acquired digital content, and if the digital content includes predetermined metadata, extracts the metadata from the digital content. The metadata extracting unit 330 outputs the extracted metadata to the metadata adding unit 360, and outputs the digital content itself to the decryption processing unit 350.

The decryption key generation unit 340 generates a decryption key necessary to implement the decryption process according to the present disclosure. That is, the decryption key generation unit 340 generates the decryption key F ^-1 based on the first distribution key D1 and the second distribution key D2. More specifically, the decryption key generation unit 340 generates the first distribution key D1 (that is, the inverse mapping U of the user key U) with respect to the second distribution key D2 (that is, the inverse mapping V ⁻¹ of the auxiliary key V). ^-1 ) and apply permutation mapping to generate a decryption key F ^-1 (ie, F ^-1 =V ^-1 ·U ^-1 ). As is clear from the above description, the decryption key F ^-1 is also a collection of numerical sequences (permutations) in which each of the numbers from 0 to 255 is arranged exclusively. Also, the decryption key F ^-1 is formed as a decryption mapping kernel K ^-1 .

The decryption processing unit 350 decrypts the encrypted digital content based on the decryption mapping kernel generated by the decryption key generation unit 340. Generally speaking, the decryption processing unit 350 first divides encrypted digital content into a plurality of regions of a predetermined size, and then applies a decryption mapping kernel to an array representing each divided region. , calculate the decoding array. Furthermore, when multiple encryption is applied, the decryption processing unit 350 sets divided regions by further dividing each divided region, applies the encryption mapping kernel K to the array indicating the divided regions, and decrypts the divided regions. Repeat the process of calculating the array. The decoding processing unit 350 outputs the calculated decoding array to the metadata adding unit 360. The encryption processing unit 240 may include, for example, a region division unit 3510 and a calculation unit 3520.

The area dividing unit 3510 divides the acquired digital content into areas of a predetermined size, that is, areas of the size of the enlarged area in the encryption process described above. That is, since the decryption process takes the reverse procedure of the encryption process, the divided area becomes an area of the size of the enlarged area during the encryption process. For example, if the divided area during encryption processing is 64 x 64 pixels, and this is taken as one block, and the enlarged area is 2 x 2 blocks vertically and horizontally, then the first divided area during decryption processing is , 128×128 pixels.

For each block of the divided area, the calculation unit 3520 calculates a decryption array by applying the corresponding decryption key in the decryption mapping kernel K ^-1 to the value of each pixel in the array corresponding to the block. do. That is, as shown in Equation 6, the calculation unit 3520 calculates the array Y by applying permutation inverse mapping F ⁻¹ (X) to each of all the elements (pixels) of the array Z indicating the divided area. do.

Note that when multiple encryption is applied, the decryption processing unit 350 repeats application of permutation inverse mapping F ⁻¹ (X) a fixed number of times while dividing the area, and finally calculates the array Y is output to the metadata adding unit 250 as the decoded original array X (decoded digital content).

The metadata adding unit 360 restores the original file format by adding the metadata extracted by the metadata extracting unit 330 to the calculated decoding sequence. The metadata adding unit 360 outputs the data set of the decoding array of the restored file format to the output control unit 260. When Null data is provided from the metadata extracting unit 330, the metadata adding unit 360 outputs the data set of the decrypted array received from the decrypting unit 350 as it is to the output control unit 370.

The output control unit 370 outputs the received data set of the decoded array to an arbitrary output destination. For example, the output control unit 370 controls the received data set of the decoded array to be stored in the file system as a data file. Alternatively, the output control unit 370 outputs the data set of the decoded array to the viewer, so that the viewer of the client 30 can interpret and display the data set as an image.

FIG. 9 is a conceptual diagram for explaining an encryption key and a decryption key in a system according to an embodiment of the present invention.

As ^described above with reference to FIG. Generate an auxiliary key V. Further, the content management device 20 distributes the inverse image U ^-1 of the user key U and the inverse image V ^-1 of the auxiliary key V to the client 30 as a first distribution key D1 and a second distribution key D2, respectively.

On the other hand, the client 30 calculates a decryption key F ⁻¹ (decryption mapping kernel K ⁻¹ ) based on the first distribution key D1 and the second distribution key D2.

Further, as shown in FIG. 2B, the first distribution key D1 and the second distribution key D2 may be generated on the client 30 side (in this example, the first distribution key D1 and the second distribution key D2 Although it is not distributed, it is referred to as a distribution key for convenience.) That is, the content management device 20 distributes the generated user key U and auxiliary key V to the client 30 as they are. The client 30 calculates an inverse image of each of the received user key U and auxiliary key V, and generates a first distribution key D1 and a second distribution key D2, which are equivalent to (a) above.

Next, for ease of understanding, an example of decoding processing will be described using FIG. 10 based on the example shown in FIG. 6. As shown in FIG. 10, the expanded array (that is, the first divided area) is an array whose elements (blocks) are each of the double-encrypted array Z.

The calculation unit 3520 first focuses on the upper left element "0" in the upper left array Z. For the upper left array Z, the upper left decryption key in the decryption mapping kernel K ^-1 is used. The calculation unit 3520 sets the 0th element "0" in the corresponding decryption key to the value of the element at the corresponding position in the array Y according to the value "0" of this element. Similarly, the calculation unit 3520 calculates, for the upper right element "2" in the upper left array Z, the 0th element "2" in the corresponding decryption key, and for the lower left element "0" in the upper left array Z, For the 0th element "0" of the corresponding decryption key, and for the lower right element "2" of the upper left array X, the 2nd element "2" of the corresponding decryption key, respectively, Set to the value of the position element.

Similarly, regarding the upper right array Z, the calculation unit 3520 sets the second element "2" in the upper right decryption key to the value of the corresponding element in the array Y for the upper left element "2". Note that in this example, the values of the elements of the upper right array Y are all the same because the values of the elements of the array Z are all the same.

Similarly, the calculation unit 3520 applies mapping using the corresponding decryption keys as described above to the lower left array Z and the lower right array Z, respectively.

After the divided area is further divided, the calculation unit 3520 performs the above calculation. That is, the calculation unit 3520 further applies mapping by the decoding mapping kernel to each array Y into which the expanded array is divided. More specifically, for the upper left element "0" in the upper left array Y, the calculation unit 3520 sets the 0th element "0" in the upper left decryption key to the value of the element at the corresponding position in the array X. Set. Similarly, for the upper right element "2" in the upper left array Y, the calculation unit 3520 sets the second element "2" in the upper right decryption key to the value of the element at the corresponding position in the array X. It should be noted that in the decryption in this case, decryption keys corresponding to the positions of the elements of the array Y are used. Similarly, the calculation unit 3520 calculates the 0th element "1" in the lower left decryption key for the lower left element "0" in the upper left array Y, and the lower right element "2" in the upper left array X. , the second element "0" in the lower right decryption key is set to the value of the element at the corresponding position in the array X, respectively.

Similarly, for the upper right array Y, the lower left array Y, and the lower right array Y in the expanded array, the calculation unit 3520 applies mapping using the corresponding decryption keys. Then, the calculation unit 3520 performs the decoding on all enlarged areas in the digital content to be decrypted.

FIG. 11 is a flowchart illustrating an example of decryption processing in a client according to an embodiment of the present invention. Such processing is realized, for example, by the client 30 executing a decryption program under the control of a processor (processor module). Such processing may be performed sequentially, or may be performed in parallel or in parallel as long as the results of the processing do not conflict. The decoding process in the client 30 will be described below, but the same applies to the decoding process in the content management device 20.

As shown in the figure, the client 30 acquires digital content to be decrypted, for example, from the content management device 20 (S1101). For example, the client 30 accesses the content management device 20 and downloads desired digital content. The downloaded digital content is digital data encrypted using the encryption technology according to the present disclosure.

Subsequently, the client 30 extracts metadata from the acquired digital content, and extracts the metadata and the digital content itself (S1102). Extracted metadata is temporarily retained in memory and/or work files.

Next, the client 30 determines whether it already holds the decryption key (S1103). If the client 30 determines that it already holds the decryption key F ^-1 (Yes in S1103), it moves to the process in S1106. On the other hand, if the client 30 determines that it does not yet hold the decryption key F ^-1 (No in S1103), it acquires the distribution key from, for example, the content management device 20 (S1104). In this example, the distribution key consists of a first distribution key and a second distribution key. The client 30 generates a decryption key F ⁻¹ (ie, a decryption mapping kernel K ⁻¹ ) based on the obtained distribution key (S1105).

Note that in this example, the client 30 acquires the distribution key after acquiring the digital content, but the invention is not limited to this. It's okay.

The client 30 that has acquired the decryption key F ^-1 then divides the acquired digital content into areas of a predetermined size corresponding to the applied N-fold encryption (N=2 in this example) (S1102). Following the example above, a 320x280 pixel image is divided into regions of 128x128 pixels each. Note that if the size of the original image is not an integral multiple of the size of the area, zero padding is performed on the part of the area that exceeds the size of the original image.

The client 30 then sets a counter COUNT (where COUNT≦N) to “1” in order to perform N-fold decoding (S1107). Subsequently, the client 30 applies mapping by the corresponding decoding mapping kernel K ^-1 to the value of each element of the array corresponding to the divided area, and calculates a decoded array (S1108). The content management device 20 applies permutation mapping using the decoding mapping kernel K ⁻¹ to all divided areas.

After applying the mapping by the decoding mapping kernel K ^-1 , the client 30 increments the value of the counter by one (S1109), and determines whether N-fold decoding is completed (S1110). In this example, since the value of the counter COUNT does not exceed N=2 (No in S1109), the client 30 returns to the process in S1106 and divides the decrypted divided area into smaller areas (S1106). .

Thereafter, the client 30 similarly applies the mapping by the decoding mapping kernel K ^-1 to each divided area to perform decoding. That is, the client 30 calculates a decryption array by applying mapping using the corresponding decryption key in the decryption mapping kernel K ^-1 to the array of each divided area (S1108). Subsequently, the client 30 increments the value of the counter COUNT by one (S1109), and determines whether the N-fold encryption is completed (S1110). In this case, since the value of the counter COUNT exceeds N=2, the N-fold decoding process ends (Yes in S1110). Next, the client 30 reads the temporarily stored metadata, adds the metadata to all the calculated data based on the decryption sequence (S1111), and adds the metadata to the data to which the metadata is added. is output as decrypted digital content (S1112).

As described above, upon acquiring digital data as encrypted digital content, the client 30 can decrypt it using the above-mentioned n-permutation mapping, restore it to the original digital content, and output it.

(Experiment example)
12A to 12C show examples in which the encryption/decryption technology according to the present disclosure is applied to images in a predetermined file format. That is, FIG. 12A shows a 320×280 pixel, 8-bit gray scale image. When the encryption technique according to the present disclosure was applied to this original image, an image as shown in FIG. 12B was obtained. As is clear from the figure, since the file format of the encrypted image is maintained, the user can check it on the viewer, but the image has no meaning to the user. Note that by applying the decoding technique according to the present disclosure to the image shown in FIG. 12B, the original image shown in FIG. 12C was restored. Note that FIG. 13 is an example of the encryption key F or the user key U. In this example, the encryption key F or the user key U is expressed as image data of 4×1024 pixels in a predetermined file format (for example, PNG format).

[Second embodiment]
This embodiment is a modification of the first embodiment, and discloses a technique for concealing the above-described user key U and auxiliary key V by applying an offset value.

To explain using FIG. 2 described above, for example, the user key generation unit 2320 holds the first offset value (p, q), while the auxiliary key generation unit 2330 holds the second offset value (r, s). Here, p and r indicate offset values in the x direction in a two-dimensional plane, and q and s indicate offset values in the y direction, but the present invention is not limited to this, and offset values in a three-dimensional space may be used. It's okay to be beaten. As an example, a first offset value (p, q) and a second offset value (r, s) are secretly embedded in the encryption program.

The user key generation unit 2320 applies the first offset value (p, q) to the generated user key U, and then outputs the offset user key U _OFFSET to the first distribution key generation unit 2340. Similarly, the auxiliary key generation unit 2330 applies the second offset value (r, s) to the generated auxiliary key V, and then sends the offset auxiliary key V _OFFSET to the second distribution key generation unit 230. Output.

As described above, the first distribution key generation unit 2340 and the second distribution key generation unit 230 calculate the inverse images of the offset user key U _OFFSET and the offset auxiliary key V _OFFSET , and use them as the first Output as a distribution key and a second distribution key.

On the other hand, if the client 30 trying to decrypt the encrypted digital content does not know the first offset value (p, q) and the second offset value (r, s), This means that the distribution key and the second distribution key cannot be obtained. Therefore, the first distribution key acquisition unit 3210 and the second distribution key acquisition unit 3220 (see FIG. 8) of the client 30 determine the first offset value (p, q) and the second offset value (r, s) in advance. It is given. As an example, a first offset value (p, q) and a second offset value (r, s) are secretly embedded in the decryption program distributed to the client 30. When the first distribution key acquisition unit 3210 and the second distribution key acquisition unit 3220 acquire the first distribution key and the second distribution key from the outside, the first distribution key acquisition unit 3210 and the second distribution key acquisition unit 3220 acquire the held first offset value (p, q) and second distribution key. The original first distribution key and second distribution key are generated by applying the offset values (r, s), respectively.

Note that the offset value may be set for each user, for example. Therefore, the decryption program can also be distributed to the client 30 with a different offset value hidden for each user embedded therein.

As described above, according to this embodiment, the user key and the auxiliary key are offset by different offset values for each user, and these are distributed as the distributed key, so even if the distributed key is unintentionally leaked, , a third party other than the authorized user cannot decrypt it unless he or she knows the offset value.

As described above, according to the present disclosure, by applying n-permutation mapping to arbitrary digital data of a multidimensional array (N-dimensional array) consisting of finite elements, without changing the external framework, That is, it becomes possible to perform encryption and decryption while maintaining the file format. This means that the implementation and operation of encryption/decryption processing can be realized on an existing system with minimal man-hours and operational load.

In particular, the encryption/decryption technology according to the present disclosure is applicable to devices that are compatible with such file formats (e.g., video/still image cameras, audio/audio equipment, etc.) in fields where general-purpose file formats are widely used. This makes it possible to protect digital data that requires a high level of confidentiality.

Further, a device implementing the encryption/decryption technology according to the present disclosure can perform encryption and decryption processing on each array element in one order. Furthermore, when the encryption/decryption device uses a GPU, its pixel shader can further speed up the processing.

Furthermore, in a device implementing the encryption/decryption technology according to the present disclosure, the user key and auxiliary key are concealed by using an offset value and then distributed as a distribution key, so even if the distribution key is Even if a third party other than the authorized user does not know the offset value, it will not be possible to properly encrypt/decrypt it even if it is leaked without the offset value being used. This enables stronger encryption/decryption of digital content. be done.

Each of the embodiments described above is an illustration for explaining the present invention, and the present invention is not intended to be limited only to these embodiments. The present invention can be implemented in various forms without departing from the gist thereof.

For example, steps, acts, or functions in the methods disclosed herein may be performed in parallel or in a different order unless the results are inconsistent. The steps, acts, and functions described are provided by way of example only, and some of the steps, acts, and functions may be omitted or combined with each other without departing from the spirit of the invention. It is also possible to add other steps, actions, or functions.

Further, although various embodiments are disclosed in this specification, specific features (technical matters) in one embodiment may be added to other embodiments while improving them as appropriate, or Certain features in the embodiments may be replaced and such forms are within the scope of the invention.

1...Computer system 10...Communication network 20...Content management device 22...Database 24...Server 210...Digital content acquisition section 220...Metadata extraction section 230...Key generation section 2310...Encryption key generation section 2320...User key generation section 2330... Auxiliary key generation section 2340...First distribution key generation section 2350...Second distribution key generation section 240...Encryption processing section 2410...Area division section 2420...Arithmetic section 2430...Expansion area setting section 250...Metadata extraction section 260...Output Control unit 30...Client 310...Digital content acquisition unit 320...Metadata extraction unit 320...Key acquisition unit 3210...First distribution key acquisition unit 3220...Second distribution key acquisition unit 340...Decryption key generation unit 350...Decryption processing unit 3510...Region dividing section 3520...Calculating section 360...Metadata extraction section 370...Output control section

Claims (20)

A system comprising an encryption device for encrypting a digital data string to be encrypted,
The encryption device includes:
an acquisition unit that acquires a first data file including the digital data string to be encrypted;
an encryption key generation unit that generates an encryption key including at least one unit key consisting of n elements having a permutation relationship;
By applying permutation mapping to the element values of the encryption target array corresponding to at least one predetermined area constituting the digital data string that is the encryption target, using the generated encryption key, an encryption processing unit that calculates at least one encryption sequence;
an output control unit that performs control to output a second data file including an encrypted digital data string indicated by the calculated at least one encryption sequence to an output destination ;
The set of the encryption target array and the permutation mapping is a group that satisfies the conditions of an associative law, the existence of an identity element, and the existence of an inverse element,
The permutation mapping converts the value of the i-th element of the encryption target array, which is indicated by the value Xi (i∈n) of one unit key element in the encryption key, to the i-th element of the encryption array. is a binary operation that sets the value of
The encryption processing unit includes:
an area dividing unit that divides the digital data string to be encrypted to set a plurality of the predetermined areas;
an arithmetic unit that calculates each of the plurality of encrypted arrays by applying the permutation mapping using the encryption key to element values of the encrypted array corresponding to each of the plurality of predetermined regions; and,
an enlarged area setting unit that sets an enlarged area based on some of the plurality of predetermined areas as a new predetermined area;
The calculation unit generates a new encryption by applying the permutation mapping to the element value of the previously calculated encryption array corresponding to the new predetermined area using the encryption key. calculate the array,
system. The encryption processing unit is configured to repeat setting of an expansion area by the expansion area setting unit and calculation of an encryption array by the calculation unit in accordance with N-fold encryption.
The system of claim 1 . The encryption device includes:
a user key generation unit that generates a user key including at least one unit key consisting of n elements having a permutation relationship;
an auxiliary key generation unit that generates an auxiliary key based on the encryption key and the inverse mapping key of the user key;
The system according to claim 1 or 2 , further comprising: A system comprising an encryption device for encrypting a digital data string to be encrypted,
The encryption device includes:
an acquisition unit that acquires a first data file including the digital data string to be encrypted;
an encryption key generation unit that generates an encryption key including at least one unit key consisting of n elements having a permutation relationship;
By applying permutation mapping to the element values of the encryption target array corresponding to at least one predetermined area constituting the digital data string that is the encryption target, using the generated encryption key, an encryption processing unit that calculates at least one encryption sequence;
an output control unit that performs control to output a second data file including an encrypted digital data string indicated by the calculated at least one encryption sequence to an output destination;
a user key generation unit that generates a user key including at least one unit key consisting of n elements having a permutation relationship;
an auxiliary key generation unit that generates an auxiliary key based on the encryption key and the inverse mapping key of the user key;
Equipped with
The set of the encryption target array and the permutation mapping is a group that satisfies the conditions of an associative law, the existence of an identity element, and the existence of an inverse element,
The permutation mapping converts the value of the i-th element of the encryption target array, which is indicated by the value Xi (i∈n) of one unit key element in the encryption key, to the i-th element of the encryption array. is a binary operation that sets the value of
system. The encryption device outputs a first distribution key based on the user key and a second distribution key based on the auxiliary key to the outside in order to enable decryption of the encrypted digital data string. composed of
The system according to claim 3 or 4 . 6. The system of claim 5 , wherein the first distribution key is an inverse image of the user key, and the second distribution key is an inverse mapping of the cryptographic key. A system further comprising a decryption device that decrypts the digital data string encrypted by the encryption device according to claim 5 or 6 , based on the first distribution key and the second distribution key. The decoding device includes:
a decryption key generation unit that generates a decryption key based on the first distribution key and the second distribution key;
a decryption processing unit that decrypts the digital data string by applying a permutation mapping to the encrypted digital data string using the generated decryption key;
8. The system of claim 7 , further comprising: The encryption device includes:
a metadata extraction unit that extracts metadata from the acquired first data file;
further comprising: a metadata adding unit that adds the extracted metadata to the encrypted digital data string to generate the second data file;
A system according to any one of claims 1 to 8 . A decryption device that decrypts a digital data string encrypted using an encryption key including at least one unit key consisting of n elements having a permutation relationship,
a decryption key generation unit that generates a decryption key corresponding to the encryption key;
By applying permutation mapping to the element values of the decryption target array corresponding to at least one predetermined region constituting the encrypted digital data string using the generated decryption key, at least a decoding processing unit that calculates one decoding array;
an output control unit that performs control to output a second data file containing a decoded digital data string indicated by the calculated at least one decoding array to an output destination ,
The set of the decoding target array and the permutation mapping is a group that satisfies the conditions of an associative law, the existence of an identity element, and the existence of an inverse element,
The permutation mapping converts the value of the i-th element of the decryption target array, which is indicated by the value Xi (i∈n) of one unit key element in the decryption key, to the i-th element of the decryption array. It is a binary operation with the value of
The decoding processing unit includes:
an area dividing unit that divides the encrypted digital data string to set a plurality of the predetermined areas;
an arithmetic unit that calculates each of the plurality of decryption arrays by applying the permutation mapping using the decryption key to element values of the decryption target array corresponding to each of the plurality of predetermined regions; and,
The area dividing unit further divides each of the plurality of predetermined areas to set a new predetermined area,
The calculation unit performs new decryption by applying the permutation mapping to the previously calculated element value of the encrypted array corresponding to the new predetermined area using the decryption key. calculate the array,
decoding device. The decryption processing unit repeats setting of a predetermined area by the area division unit and calculation of a decryption array by the calculation unit in response to the encrypted digital data string to which N-fold encryption has been applied. configured as,
The decoding device according to claim 10 . A decryption device that decrypts a digital data string encrypted using an encryption key including at least one unit key consisting of n elements having a permutation relationship,
a decryption key generation unit that generates a decryption key corresponding to the encryption key;
By applying permutation mapping to the element values of the decryption target array corresponding to at least one predetermined region constituting the encrypted digital data string using the generated decryption key, at least a decoding processing unit that calculates one decoding array;
an output control unit that performs control to output a second data file including a decoded digital data string indicated by the calculated at least one decoding array to an output destination;
a first distribution key acquisition unit that acquires a first distribution key based on the encryption key;
a second distribution key acquisition unit that acquires a second distribution key based on a user key including at least one unit key consisting of n elements having a permutation relationship ;
The set of the decoding target array and the permutation mapping is a group that satisfies the conditions of an associative law, the existence of an identity element, and the existence of an inverse element,
The permutation mapping converts the value of the i-th element of the decryption target array, which is indicated by the value Xi (i∈n) of one unit key element in the decryption key, to the i-th element of the decryption array. It is a binary operation with the value of
the first distribution key is an inverse mapping of the user key;
The second distribution key is generated based on the encryption key and the inverse mapping of the user key,
The decryption key generation unit generates the decryption key based on the first distribution key and the second distribution key.
decoding device. An encryption method executed in a computer device for encrypting a digital data string to be encrypted, the method comprising:
obtaining a first data file containing the digital data string to be encrypted;
Generating an encryption key including at least one unit key consisting of n elements having a permutation relationship;
By applying permutation mapping to the element values of the encryption target array corresponding to at least one predetermined area constituting the digital data string that is the encryption target, using the generated encryption key, calculating at least one encrypted sequence;
Controlling for outputting a second data file containing an encrypted digital data string indicated by the calculated at least one encrypted sequence to an output destination ,
The set of the encryption target array and the permutation mapping is a group that satisfies the conditions of an associative law, the existence of an identity element, and the existence of an inverse element,
The permutation mapping converts the value of the i-th element of the encryption target array, which is indicated by the value Xi (i∈n) of one unit key element in the encryption key, to the i-th element of the encryption array. It is a binary operation with the value of
Calculating the encrypted sequence includes:
dividing the digital data string to be encrypted to set a plurality of predetermined areas;
calculating each of the plurality of encrypted arrays by applying the permutation mapping using the encryption key to element values of the encrypted array corresponding to each of the plurality of predetermined regions; ,
setting an enlarged area based on some of the plurality of predetermined areas as a new predetermined area;
Calculating each of the plurality of encrypted arrays includes performing the permutation mapping on the element values of the previously calculated encrypted array corresponding to the new predetermined area using the encryption key. calculating a new cryptographic sequence by applying
Encryption method. An encryption method executed in a computer device for encrypting a digital data string to be encrypted, the method comprising:
obtaining a first data file containing the digital data string to be encrypted;
Generating an encryption key including at least one unit key consisting of n elements having a permutation relationship;
By applying permutation mapping to the element values of the encryption target array corresponding to at least one predetermined area constituting the digital data string that is the encryption target, using the generated encryption key, calculating at least one encrypted sequence;
Controlling for outputting a second data file containing an encrypted digital data string indicated by the calculated at least one encrypted sequence to an output destination ;
Generating a user key including at least one unit key consisting of n elements having a permutation relationship;
generating an auxiliary key based on the encryption key and the inverse mapping key of the user key,
The set of the encryption target array and the permutation mapping is a group that satisfies the conditions of an associative law, the existence of an identity element, and the existence of an inverse element,
The permutation mapping converts the value of the i-th element of the encryption target array, which is indicated by the value Xi (i∈n) of one unit key element in the encryption key, to the i-th element of the encryption array. is a binary operation with the value of
Encryption method. A decryption method for decrypting a digital data string encrypted using an encryption key including at least one unit key consisting of n elements having a permuted relationship, the method being executed in a computer device, the method comprising:
generating a decryption key corresponding to the encryption key;
By applying permutation mapping to the element values of the decryption target array corresponding to at least one predetermined region constituting the encrypted digital data string using the generated decryption key, at least calculating one decoding array;
Controlling for outputting a second data file containing a decoded digital data string indicated by the calculated at least one decoding array to an output destination,
The set of the decoding target array and the permutation mapping is a group that satisfies the conditions of an associative law, the existence of an identity element, and the existence of an inverse element,
The permutation mapping converts the value of the i-th element of the decryption target array, which is indicated by the value Xi (i∈n) of one unit key element in the decryption key, to the i-th element of the decryption array. It is a binary operation with the value of
Calculating the decoding array includes:
dividing the encrypted digital data string to set a plurality of the predetermined areas;
calculating each of the plurality of decryption arrays by applying the permutation mapping using the decryption key to element values of the decryption target array corresponding to each of the plurality of predetermined regions; , including;
Setting the plurality of predetermined regions includes further dividing each of the plurality of predetermined regions to set a new predetermined region,
Calculating each of the plurality of decryption arrays includes applying the permutation mapping to the element values of the previously calculated encrypted array corresponding to the new predetermined area using the decryption key. calculating a new decoding array by applying
Decryption method. A decryption method for decrypting a digital data string encrypted using an encryption key including at least one unit key consisting of n elements having a permuted relationship, the method being executed in a computer device, the method comprising:
generating a decryption key corresponding to the encryption key;
By applying permutation mapping to the element values of the decryption target array corresponding to at least one predetermined region constituting the encrypted digital data string using the generated decryption key, at least calculating one decoding array;
Controlling for outputting a second data file containing a decoded digital data string indicated by the calculated at least one decoding array to an output destination;
obtaining a first distribution key based on the encryption key;
obtaining a second distribution key based on a user key including at least one unit key consisting of n elements having a permutation relationship;
The set of the decoding target array and the permutation mapping is a group that satisfies the conditions of an associative law, the existence of an identity element, and the existence of an inverse element,
The permutation mapping converts the value of the i-th element of the decryption target array, which is indicated by the value Xi (i∈n) of one unit key element in the decryption key, to the i-th element of the decryption array. It is a binary operation with the value of
the first distribution key is an inverse mapping of the user key;
The second distribution key is generated based on the encryption key and the inverse mapping of the user key,
Generating the decryption key includes generating the decryption key based on the first distribution key and the second distribution key,
Decryption method. A computer program that causes a computing device to implement an encryption method for encrypting a digital data string to be encrypted, the computer program comprising:
The encryption method includes:
obtaining a first data file containing the digital data string to be encrypted;
Generating an encryption key including at least one unit key consisting of n elements having a permutation relationship;
By applying permutation mapping to the element values of the encryption target array corresponding to at least one predetermined area constituting the digital data string that is the encryption target, using the generated encryption key, calculating at least one encrypted sequence;
Controlling for outputting a second data file containing an encrypted digital data string indicated by the calculated at least one encrypted sequence to an output destination ,
The set of the encryption target array and the permutation mapping is a group that satisfies the conditions of an associative law, the existence of an identity element, and the existence of an inverse element,
The permutation mapping converts the value of the i-th element of the encryption target array, which is indicated by the value Xi (i∈n) of one unit key element in the encryption key, to the i-th element of the encryption array. It is a binary operation with the value of
Calculating the encrypted sequence includes:
dividing the digital data string to be encrypted to set a plurality of predetermined areas;
calculating each of the plurality of encrypted arrays by applying the permutation mapping using the encryption key to element values of the encrypted array corresponding to each of the plurality of predetermined regions; ,
including setting an enlarged area based on some of the plurality of predetermined areas as a new predetermined area,
Calculating each of the plurality of encrypted arrays includes performing the permutation mapping on the element values of the previously calculated encrypted array corresponding to the new predetermined area using the encryption key. calculating a new encryption sequence by applying
computer program. A computer program that causes a computing device to implement an encryption method for encrypting a digital data string to be encrypted, the computer program comprising:
The encryption method includes:
obtaining a first data file containing the digital data string to be encrypted;
Generating an encryption key including at least one unit key consisting of n elements having a permutation relationship;
By applying permutation mapping to the element values of the encryption target array corresponding to at least one predetermined area constituting the digital data string that is the encryption target, using the generated encryption key, calculating at least one encrypted sequence;
Controlling for outputting a second data file containing an encrypted digital data string indicated by the calculated at least one encrypted sequence to an output destination;
Generating a user key including at least one unit key consisting of n elements having a permutation relationship;
generating an auxiliary key based on the encryption key and the inverse mapping key of the user key,
The set of the encryption target array and the permutation mapping is a group that satisfies the conditions of an associative law, the existence of an identity element, and the existence of an inverse element,
The permutation mapping converts the value of the i-th element of the encryption target array, which is indicated by the value Xi (i∈n) of one unit key element in the encryption key, to the i-th element of the encryption array. is a binary operation with the value of
computer program. A computer that realizes a decryption method for decrypting a digital data string encrypted using an encryption key including at least one unit key consisting of n elements having a permuted relationship, which is executed in a computer device. A program,
The decoding method includes:
generating a decryption key corresponding to the encryption key;
By applying permutation mapping to the element values of the decryption target array corresponding to at least one predetermined region constituting the encrypted digital data string using the generated decryption key, at least calculating one decoding array;
Controlling for outputting a second data file containing a decoded digital data string indicated by the calculated at least one decoding array to an output destination,
The set of the decoding target array and the permutation mapping is a group that satisfies the conditions of an associative law, the existence of an identity element, and the existence of an inverse element,
The permutation mapping converts the value of the i-th element of the decryption target array, which is indicated by the value Xi (i∈n) of the element of one of the unit keys in the decryption key, to the i-th element of the decryption array. It is a binary operation with the value of
Calculating the decoding array includes:
dividing the encrypted digital data string to set a plurality of the predetermined areas;
calculating each of the plurality of decryption arrays by applying the permutation mapping using the decryption key to element values of the decryption target array corresponding to each of the plurality of predetermined regions; , including;
Setting the plurality of predetermined regions includes further dividing each of the plurality of predetermined regions to set a new predetermined region,
Calculating each of the plurality of decryption arrays includes applying the permutation mapping to the element values of the previously calculated encryption array corresponding to the new predetermined area using the decryption key. calculating a new decoding array by applying
computer program. A computer that realizes a decryption method for decrypting a digital data string encrypted using an encryption key including at least one unit key consisting of n elements having a permuted relationship, which is executed in a computer device. A program,
The decoding method includes:
generating a decryption key corresponding to the encryption key;
By applying permutation mapping to the element values of the decryption target array corresponding to at least one predetermined region constituting the encrypted digital data string using the generated decryption key, at least calculating one decoding array;
Controlling for outputting a second data file containing a decoded digital data string indicated by the calculated at least one decoding array to an output destination;
obtaining a first distribution key based on the encryption key;
obtaining a second distribution key based on a user key including at least one unit key consisting of n elements having a permutation relationship;
The set of the decoding target array and the permutation mapping is a group that satisfies the conditions of an associative law, the existence of an identity element, and the existence of an inverse element,
The permutation mapping converts the value of the i-th element of the decryption target array, which is indicated by the value Xi (i∈n) of one unit key element in the decryption key, to the i-th element of the decryption array. It is a binary operation with the value of
the first distribution key is an inverse mapping of the user key;
The second distribution key is generated based on the encryption key and the inverse mapping of the user key,
Generating the decryption key includes generating the decryption key based on the first distribution key and the second distribution key,
computer program.

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