JP2003345243A - Convolution encryption method, convolution encryption system, and convolution encryption program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance cipher intensity while suppressing the amount of information processing relating to a file including not only an image file but a text file as well. <P>SOLUTION: A plurality of partial files are formed by dividing the file to be encrypted to the same length (step S1). Next, one among the other partial files exclusive of the one partial file is used as a cipher code for encrypting the one partial file and in this encryption, the exclusive-OR of the one partial file and the partial file used for the cipher code is calculated, by which the convolution encryption is performed (step S3). <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a convolutional encryption method, a convolutional encryption device and a convolutional encryption program.

[0002]

2. Description of the Related Art In recent years, with the development of high-speed communication technology on the Internet and high compression technology for video data, video,
Content such as music and computer game software has come to be distributed via a communication line. Then, in order to prevent illegal downloading and illegal copying of content distributed via a communication line such as the Internet, the content file is generally encrypted and distributed.

[0003]

By the way, although contents including video are large-capacity files, the conventional encryption system has the following two problems in encrypting large-capacity files. First, in order to encrypt a large-capacity file with a desired encryption strength, a large amount of information processing is required, so even if a high-performance CPU is used, it takes a long time and the CPU is overloaded, resulting in smooth content distribution. It hinders service. This problem is exacerbated when decrypting a large encrypted file. Secondly, if an attempt is made to encrypt a large-capacity file while maintaining a smooth content distribution service, the encryption strength will inevitably weaken, and it will be easy for a person who illegally downloaded or copied the information to decrypt it. In addition, the above two problems are a correlative relationship (trade-off), and if encryption strength is increased, it takes time for encryption / decryption, and if encryption / decryption is attempted in a short time, the encryption strength is Will fall.

As a method of solving the above-mentioned two problems, an image file as a content is divided into a plurality of divided files to make a plurality of divided files, and noise is added to each divided file for encryption to make an encrypted divided file. , The encrypted image files are sent to the legitimate user in an irregular order, the code that joins the encrypted segment files is also sent to the legitimate user, and the legitimate user decrypts and joins the encrypted segment files to create the original image file. A split partial encryption method has been devised, which is to restore to.

However, the divided partial encryption method is an encryption method on the assumption that the content to be distributed is an image file. For example, a text file containing important personal information or the like may be partially included. There is a problem that the encryption strength is insufficient to make it unreadable.

As a method for generally solving the above-mentioned problems including a text file and the like, there is known a Vernam cipher which performs encryption using an encryption code having the same data length as plain text. Has been. In particular, the one-time pad method, which uses the encryption code only once in the Vernam cipher, is known as an undecipherable cipher.

However, the Vernam cryptosystem has a problem that the cryptographic code is too long (the information amount of the cryptographic code is too large) and is not put into practical use except a special exception.

The present invention has been made in view of the above-mentioned circumstances, and is a convolutional encryption method capable of increasing encryption strength while suppressing the amount of information processing for files including text files as well as image files. , A convolutional encryption device and a convolutional encryption program are provided.

[0009]

In order to achieve the above object, in the invention according to claim 1, the encrypted file is divided into the same length to form a plurality of partial files, and one partial file is formed. As the encryption code for encrypting a file, one of the other partial files other than the one partial file is used, and in the encryption, the exclusion of the one partial file and the partial file used for the encryption code It is characterized by calculating logical OR.

Further, the invention according to claim 2 is characterized in that each of the partial files is used as the encryption code a maximum of two times.

Further, the invention according to claim 3 is characterized in that replacement encryption processing is added to at least one of the encrypted file and the partial file before performing the encryption.

Further, in the invention as set forth in claim 4, a file unrelated to the partial file and the encrypted file is used as an encryption code for encrypting one of the plurality of partial files. Characterize.

Further, in the invention according to claim 5, when the encrypted partial file is transmitted from the transmission source to the transmission destination, a decryption code for decrypting the partial file is transmitted from the transmission source. It is characterized in that it is transmitted twice first.

Further, in the invention according to claim 6, in at least one stage before or after encrypting the partial file, the partial file is operated by a hash function to calculate a first hash code, and the encryption is performed. After the encrypted partial file is transmitted from the transmission source to the transmission destination and before or after decrypting the partial file, the second hash code is calculated by a hash function for the partial file. Is calculated and the first hash code and the second hash code are compared with each other.

In order to achieve the above-mentioned object, in the invention according to claim 7, a block forming means for dividing the encrypted file into the same length to create a plurality of partial files, and the partial file. And convolutional Vernam-encryption means for calculating the exclusive OR of the partial files excluding the partial file.

In order to achieve the above-mentioned object, in the invention described in claim 8, the step of dividing the encrypted file into the same length to create a plurality of partial files,
A step of calculating an exclusive logical sum of the partial file and the partial files excluding the partial file.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 is a flow chart showing the outline of a convolutional encryption method according to the first embodiment of the present invention.
In this embodiment, a source file (file to be encrypted) is divided into a plurality of partial files having the same length, and the partial file is used as an encryption code of another partial file.
Partial files are mutually encrypted (Vernam encryption). Further, in the present embodiment, the diagram showing the order of encrypting each partial file with the partial file is similar to a state in which shoelaces are tied, and is therefore called a "shoe string" method. The present embodiment will be specifically described below.

<Blocking> Data is normalized as a preparatory work before the Vernam encryption. The normalization of this data corresponds to steps S1 and S2 in FIG.
To normalize the data, first, the source file is divided into 2M (M is an integer of 1 or more) partial files (partial files) having the same length to form blocks.
16 bytes to 24 bytes for each partial file
A hash code having an arbitrary length of bytes is created and set as a "partial file hash code" (step S1).

The hash code is a hash code obtained by calculating a value indicated by the partial file with a predetermined hash function. The hash function is a function that generates a fixed-length pseudo random number (hash code) from a given original text (here, a partial file). Since the hash function contains an irreversible one-way function, the partial file cannot be reproduced from the hash code.

<Normalization of Each Block> Next, each partial file is normalized by performing replacement encryption (scramble) to obtain a "replacement partial file" (step S).
2). The replacement encryption is an encryption method that replaces each symbol with another symbol according to a predetermined rule with respect to a symbol string made up of numbers or letters forming an encrypted file (partial file). In this encryption method, the rule for replacing symbols is an encryption key (replacement code). Also, the replacement code is different for each partial file. Different codes are those having different code lengths or code tables.

In step S2, the following processing is also performed. That is, in step S2, a hash code is created for the replacement partial file, and is set as "scramble / partial file hash code". Further, step S2
In, the replacement partial file is divided again into a plurality of partial files (fragment files). Then, the fragment files are recombined by the substitution combination table to create 2N (N is an integer of 1 or more) “code files”. Creation of these fragment files and code files is a process for completely removing the order of the data that the source files have. Next, a hash code is created for each code file, and is set as a “code file hash code”.

<Convolutional Vernam Encryption> Next, convolutional Vernam encryption processing is performed (step S3). This convolutional Vernam encryption process will be specifically described with reference to FIGS. 2 to 7. FIG. 2 is a conceptual diagram showing an example of the convolutional Vernam encryption process.

In the convolutional Vernam encryption process, the source file (file to be encrypted) is divided into the same length to form a plurality of partial files, and the partial files other than the partial file are used as encryption codes for encrypting each partial file. It uses partial files. In this embodiment, the code files P _{1 to} P _2M created in the process of step S2 are used as the partial files.

The procedure for convolutional Vernam encryption of the code files P _{1 to} P _n will be described with reference to FIG. In FIG. 2, the code file P ₂ is used as the encryption code when the code file P ₁ is Vernam-encrypted, and the code file P ₃ is used as the encryption code when the code file P ₂ is Vernam-encrypted. using the code file P ₄ to P ₃ as the cipher code when Vernam encryption, sequentially repeating such encryption, a code file P _n code file P _n-1 as the cipher code when Vernam encryption The code file P ₁ is used as an encryption code for the Vernam encryption of the code file P _n .

When the result of the convolutional Vernam encryption is the encrypted file Q, the creation of the encrypted file Q can be expressed by the following mathematical formula. Q _i = P _i ◎ P _{i + 1} Q _n = P _n ◎ P ₁ Here, the symbol ⊚ indicates an exclusive OR, and i is an integer from 1 to n. The truth table of the exclusive OR is as shown in FIG.

In the formation of the convolutional Vernam cipher, when the set of encrypted files is Q and the set of encryption codes is P, the repetitive operations Q ₁ ◎ Q ₂ ◎ ... Q _X are the elements of the set Q. In the case of reducing the repeated operation Q _α ◎ Q _β ◎ ... Q _ω by any of the repeated operations by the elements of the set Q to the decompression (decoding) of the set Q, this state is mathematically determined. Can be said to be closed.

There are infinite number of arithmetic procedures for realizing such a system, but the simplest one is the one-stroke algorithm, and a typical one is the "ring" shown in FIG. And the “shoelace” algorithm shown in FIGS. 3 and 4. The algorithm for using such an encryption code (circular ring algorithm, shoelace algorithm) is called “shoelace method” in convolutional Vernam encryption.

Next, the procedure for convoluting the code files P ₁ -P _2n with the shoelace method for convolutional Vernam encryption will be described with reference to FIGS. 3 and 4. 3 and 4 are conceptual diagrams showing a shoelace algorithm in the shoelace system. Figure 3
4 is different only in the selection method of other code files used when the code file is encrypted.

First, the code files P _{1 to} P _n are Vernam-encrypted using the code files P _{n + 1 to} P _2n to create an encrypted file Q _i . If this is expressed by a mathematical expression, for example, it will be as follows. Q _i = P _i ◎ P _{n + i} Then, the code files P _{n + 1 to} P _2n are Vernam-encrypted using the code files P _{n to} P ₁ and encrypted file Q
Create _{n + i} . If this is expressed by a mathematical expression, for example, it will be as follows. Q _{n + i} = P _{n + i} ◎ P _{n-i + 1}

Next, a concrete example of the procedure of convolutive Burnham encryption using the shoelace method will be described with reference to FIG. In this specific example, a case will be described where the code files P _{1 to} P ₄ are subjected to convolutional Vernam encryption. 6 (a) is a conceptual diagram showing another selection method code files P ₁ to P ₄ to be used to encrypt the code file P ₁ to P _4, FIG. 6 (b) code file P _{1 5} is a conceptual diagram showing encrypted files Q _{1 to} Q ₄ that are the results of encrypting P ₄ to P ₄ .

The encrypted file Q ₁ is the code file P ₁
Since it is obtained by the exclusive OR of (1010) and the code file P ₂ (1110), it becomes Q ₁ (0100).
The encrypted file Q ₂ is the code file P ₂ (1110)
And the code file P ₃ (1011) are obtained by exclusive OR, so that Q ₂ (0101) is obtained. Since the encrypted file Q ₃ is obtained by the exclusive OR of the code file P ₃ (1011) and the code file P ₄ (0001), it becomes Q ₃ (1010). The encrypted file Q ₄ is the code file P ₄ (0001) and the code file P ₁ (1
010) is obtained by exclusive OR, so Q ₄ (10
11).

<Sending of Code> When the source file is encrypted in steps S1 to S3, the encrypted information (encrypted files Q _{1 to} Q _2n ), the decryption code and the hash code for checking are encoded. The decryption information such as is transmitted to the destination via the network or the like (step S4). The transmission source that performs the encryption in steps S1 to S3 corresponds to, for example, a person who delivers contents such as images and sounds to the user via the Internet, or a person who communicates personal information such as bank deposit information.

The decryption information transmitted in step S4 includes
The following are listed. 1) Code file P ₁ -created in step S2
Arbitrary code file P _{k of} P _2M (the same code file P _k is sent twice for each transmission of one piece of decryption information) 2) Each encrypted file Q _{1 to} Q _2n number K 3) Step S2 Code file / hash code 4) created in step S2) Substitution combination table used in conversion from fragment file to code file in step S2 5) Scramble / partial file / hash code 6) step created in step S2 Replacement code group 7 used for replacement encryption in S2) Partial file hash code created in step S1

Destination (user) who received the decryption information
Performs the decoding shown in steps S5 to S7 below.

<Decryption of Convolutional Vernam Cryptography> Decryption
First, it was encrypted with the convolutional Vernam cipher
Encrypted file Q₁~ Q_2nIs decrypted (step S
5). As a pre-process for this decryption, the destination is the decryption code.
Encrypted file P _kCheck the legitimacy of
It That is, the encrypted file P transmitted twice_k
(Encrypted file P_k1, Encrypted file P_k2) To each other
The exclusive OR operation and the operation result is
B). The calculation result is "all
If not "zero", encrypted file Q_k1And encryption file
Il Q_k2Detected that the decoding code is not correct
To be done.

Next, an inverse Vernam operation is performed in order to decrypt the encrypted files Q _{1 to} Q _2n subjected to the convolutional Vernam encryption. The inverse Burnham operation is an inverse operation of the exclusive OR operation between the code files P _{1 to} P _2n performed in step S3. A specific procedure of this inverse Vernam calculation will be described with reference to FIG. FIG. 7 is a conceptual diagram showing a decryption procedure of the encrypted files Q _{1 to} Q ₄ . The specific numerical values shown in FIG. 7 are the same as the numerical values in the specific example of the convolutional Vernam encryption shown in FIG.

First, as shown in FIG. 7A, the code file P which is the code file P _k received by the transmission destination.
The exclusive OR of ₄ (0001) and the encrypted file Q ₄ (1011) is calculated. The result of this calculation is a code file P ₁ (1010) as shown in FIG. Next, as shown in FIG. 7B, the exclusive OR of the decrypted code file P ₁ (1010) and the encrypted file Q ₄ (1011) is calculated. The result of this operation is the code file P ₄ (0001). Then, as shown in FIG. 7C, the exclusive OR of the decrypted code file P ₄ (0001) and the encrypted file Q ₃ (1010) is obtained. The result of this calculation is the code file P ₃ (1011). Then, as shown in FIG. 7D, the decrypted code file P ₃ (1011) and the encrypted file Q ₂ (0
101) and the exclusive OR. The result of this calculation is the code file P ₂ (1110). By these, the encrypted files Q _{1 to} Q ₄ are decrypted and the code file P
_{1 to} P ₄ are restored.

Next, for each of the code files P _{1 to} P _2N restored by the inverse Vernam calculation, a hash code is created by the same function as the hash function used in creating the "partial file hash code" in step S1. , "Partial file hash code".
Then, a partial file hash code generated in step S1, by that Tsukiawasu a partial file hash code created in this step S5, and confirms the validity of the restored code file P ₁ to P _2M . This completes the convolutional Vernam-cipher decryption process (step S5).

<Decryption of Replacement Cipher> Next, step S
The replacement encryption (scramble) performed in 2 is decrypted (step S6). Specifically, first, for each code file P ₁ to P _2N decrypted in step S5, to restore the replaced partial file using displacement binding table a destination is received as one of the decoded information.

Next, for each restored replacement partial file, a hash code is created by the same function as the hash function used in the creation of "scramble / partial file / hash code" in step S2, and "scramble / partial file / hash code" is created. Hash code ”. Then, the scramble / partial file / hash code created in step S2 is compared with the scramble / partial file / hash code created in step 6 to confirm the validity of each restored replacement partial file. To do.

Next, each replacement partial file restored above is decoded using the replacement code group received by the transmission destination as one of the pieces of decoding information, and restored into a partial file. Next, for each restored partial file, a hash code is created using the same function as the hash function used in creating the "partial file hash code" in step S1 to obtain a "partial file hash code". Then, the partial file created in step S1
The validity of each restored partial file is confirmed by matching the hash code with the partial file hash code created in step 6. This allows
The replacement encryption decryption process (step S6) ends.

<Combining Blocks> Next, the restored partial files are combined to restore the source file (step S7).

As a result, according to the present embodiment, the source file is divided into a plurality of partial files having the same length and the partial files are used as encryption codes, so that the encryption strength equal to or higher than that of the conventional Vernam encryption is obtained. While having
The length of the cipher code can be made extremely shorter than that of the conventional Vernam cipher, and the Vernam cipher can be put into practical use.

Further, according to the present embodiment, since the code file (partial file) which is the encryption code in the convolutional Vernam encryption is used at most twice, it is possible to perform encryption with high encryption strength.

Further, according to the present embodiment, since the data is normalized as a pre-processing of the convolutional Vernam encryption (step S2 etc.) and the data is scrambled by the replacement encryption or the like, the source file has a regularity. Even if some data (text data, etc.) is included, its regularity can be entirely eliminated, and encryption with high encryption strength can be performed.

Further, according to the present embodiment, since the code file, which is the decryption code, is transmitted twice and the validity of the hash code is verified at each stage of decryption, the decryption code error is detected. You can also check if there is a communication error, falsification of information, etc.

(Second Embodiment) Next, a convolutional encryption method according to a second embodiment of the present invention will be described with reference to FIGS.
Will be described with reference to. In the first embodiment, it is necessary to transmit a partial file (code file) as a decryption code from the transmission source to the transmission destination. Here, when the encryption strength of the transmitted partial file is low, there is a possibility that the partial file will be eavesdropped and decrypted in the course of communication. Therefore, in the present embodiment, as the decryption code to be transmitted from the transmission source to the transmission destination, the convolutional Vernam encryption of the external key method using the "external code" which is a random file unrelated to the source file is performed. Less than,
This embodiment will be specifically described.

The large flow of encryption at the transmission source and decryption at the transmission destination in this embodiment is the same as in the first embodiment, and FIG. 1 is also a flow chart showing the convolutional encryption method of this embodiment. .

<Blocking><Normalization of Each Block> First, the data is normalized as a preparatory work before the Vernam encryption. The normalization of this data is performed by step S1 (blocking) in FIG.
Although it corresponds to S2 (normalization of each block),
Since the same processing as steps S1 and S2 of the first embodiment is performed, description thereof will be omitted.

<Convolutional Vernam Encryption> Next, convolutional Vernam encryption processing is performed (step S3). This convolutional Vernam encryption process uses the "foreign key method" different from that of the first embodiment, and will be specifically described with reference to FIG. FIG. 8 is a conceptual diagram showing a convolutional encryption algorithm of the external key method according to the second embodiment of the present invention.

In the convolutional Vernam encryption process of the external key system, a source file (file to be encrypted) is divided into the same length to form a plurality of partial files, and each partial file is encrypted as an encryption code. The convolutional Vernam-encryption process of the shoelace method of the first embodiment is common in that a partial file other than the partial file is used, but an encryption code for encrypting one of a plurality of partial files. The difference is that it uses a file (external code) that is unrelated to the source file. In this embodiment, the code files P _{1 to} P _2n created in the process of step S2 are used as the partial files.

First, as shown in FIG. 8, the code files P _{1 to} P _n are Vernam-encrypted using the code files P _{n + 1 to} P _2n to create an encrypted file Q _i . If this is expressed by a mathematical expression, for example, it will be as follows. Q _i = P _i ◎ P _{n + i}

Next, any one of the code files P _{n + 1 to} P _2n is designated, and this is designated as a code file P _k . The code file P _{n + 1} ~P _2n (code file P _k excluding) the code file P _{n + 1} ~P _2n (code file P excluding _k) encrypted files by Vernam encrypted using the Q _{n +} Create _i (except encrypted file Q _k ). If this is expressed by a mathematical expression, for example, it will be as follows. Q _{n + i} = P _{n + i} ◎ P _{n-i + 1} (where i is an integer of 1 or more excluding K)

Next, the code file P _k is Vernam-encrypted using the external code T to create an encrypted file Q _k . If this is expressed by a mathematical expression, for example, it will be as follows. Q _k = P _k ⊚T Here, the external code T is a file unrelated to the source file and is data having the same length as the code files P _{n + 1 to} P _2n . Further, the external code T is preferably composed of random numbers.

<Sending of Code> When the source file is encrypted in steps S1 to S3, the encrypted information (encrypted files Q _{1 to} Q _2n ), the decryption code and the hash code for checking are coded. The decryption information such as is transmitted to the destination via the network or the like (step S4). The decryption information transmitted in step S4 includes the following. 1) External code T (the same external code T is sent twice for each transmission of one piece of decryption information) 2) Master code file number K 3 which is the file number of the above code file P _k ) Created in step S2 Code file / hash code 4) Replacement combination table used for conversion from fragment file to code file in step S2 5) Scramble / partial file / hash code 6) created in step S2 Replacement in step S2 Substitution code group 7 used for encryption 7) Partial file hash code created in step S1

Destination (user) who received the decryption information
Performs the decoding shown in steps S5 to S7 below.

<Decryption of Convolutional Vernam Cipher> For decryption, first, the encrypted files Q _{1 to} Q _2n encrypted by the convolutional Vernam cipher are decrypted (step S).
5). As a preprocess for this decryption, the transmission destination confirms the correctness of the external code T that is the decryption code. That is, the exclusive OR operation is performed on the external codes T (external code T ₁ , external code T ₂ ) transmitted twice, and it is confirmed that the operation result is “all zeros”.

Next, an inverse Vernam operation is performed to decrypt the encrypted files Q _{1 to} Q _2n that have been subjected to the convolutional Vernam encryption. The inverse Burnham operation is an inverse operation of the exclusive OR operation between the code files P _{1 to} P _2n (excluding the code file P _k ) and the external code T performed in step S3.

The process after the inverse Vernam calculation is the same as the process after the inverse Vernam calculation of the first embodiment, and <decryption of permutation cipher> is performed in step S6, and step S6 is performed.
<Concatenation of blocks> is performed at 7.

Thus, according to this embodiment, the first
Since the "external code T", which is a random file unrelated to the source file, is used as the decryption code while performing the convolutional Vernam-encryption similar to the embodiment, the decryption code transmitted / received via the network or the like, for example. The encryption strength of can be increased.

In the above embodiment, step S in FIG.
A program for realizing the function of performing the encryption shown in 1 to S3 or the decryption shown in steps S5 to S7 of FIG. 1 is recorded in a computer-readable recording medium, and the program recorded in this recording medium is stored in a computer. The distribution destination information writing process may be performed by causing the system to read and execute. The "computer system" may include an OS and hardware such as peripheral devices. In addition, if the "computer system" uses a WWW system,
The homepage provision environment (or display environment) is also included. The "computer-readable recording medium" means a flexible disk, a magneto-optical disk, an R
It refers to a portable medium such as OM and CD-ROM, and a storage device such as a hard disk built in a computer system.

Further, the "computer-readable recording medium" means a volatile memory (RAM) inside a computer system which serves as a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. ), Which holds the program for a certain period of time. The program may be transmitted from a computer system that stores the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the "transmission medium" for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. Further, the program may be a program for realizing some of the functions described above. Further, it may be a so-called difference file (difference program) that can realize the above-mentioned functions in combination with a program already recorded in the computer system.

Although the embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes and the like within the scope not departing from the gist of the present invention. included.

[0064]

As is apparent from the above description, according to the present invention, the encrypted file is divided into the same length to form a plurality of partial files, and the partial code is encrypted as an encryption code. Since other partial files are used, the encryption strength can be increased while suppressing the information processing amount.

Further, according to the present invention, by using a file unrelated to the partial file and the encrypted file as one of the encryption codes, the decryption code transmitted / received via the network etc. The encryption strength can be increased.

[Brief description of drawings]

FIG. 1 is a flowchart showing an outline of a convolutional encryption method according to a first embodiment of the present invention.

FIG. 2 is a conceptual diagram showing an example of a convolutional Vernam encryption process (circular algorithm).

FIG. 3 is a conceptual diagram showing an example of a convolutional Vernam encryption process (shoelace algorithm).

FIG. 4 is a conceptual diagram showing an example of a convolutional Vernam encryption process (shoelace algorithm).

FIG. 5 is a diagram showing a truth table of exclusive OR.

FIG. 6 is a conceptual diagram showing a specific example of a procedure for performing convolutional Vernam encryption using a shoelace method.

FIG. 7 is a conceptual diagram showing a specific example of inverse Vernam calculation.

FIG. 8 is a conceptual diagram showing a foreign key type convolutional encryption algorithm according to the second embodiment of the present invention.

[Explanation of symbols]

P ₁ ~P _2n, P _k code file (partial file) Q ₁ to P ₄ encrypted file T external code

Claims (8)

[Claims] 1. An encrypted file is divided into the same length to form a plurality of partial files, and an encryption code for encrypting one partial file is used as an encryption code for other partial files excluding the one partial file. A convolutional encryption method, wherein one of them is used to calculate an exclusive OR of the one partial file and a partial file used for an encryption code in the encryption. 2. The convolutional encryption method according to claim 1, wherein each of the partial files is used as the encryption code a maximum of two times. 3. The convolutional encryption method according to claim 1, wherein replacement encryption processing is applied to at least one of the encrypted file and the partial file before performing the encryption. . 4. The file unrelated to the partial file and the encrypted file is used as an encryption code for encrypting one of the partial files. The convolutional encryption method according to any one of 1. 5. When transmitting the encrypted partial file from a transmission source to a transmission destination, a decryption code for decrypting the partial file is transmitted from the transmission source to the transmission destination twice. The convolutional encryption method according to any one of claims 1 to 4, which is characterized in that. 6. The at least one stage before or after encrypting the partial file calculates a first hash code by operating a hash function on the partial file, and the encrypted partial file is a sender. From the destination to the destination and before or after the partial file is decrypted, at least one stage of the partial file operation is performed with a hash function to calculate a second hash code, and the first hash value is calculated. 6. A process for comparing a code with the second hash code is included.
The convolutional encryption method according to any one of 1. 7. A blocking unit that divides the encrypted file into the same length to create a plurality of partial files, and calculates an exclusive OR of the partial files and the partial files excluding the partial files. A convolutional encryption device, comprising: 8. A step of dividing an encrypted file into the same length to create a plurality of partial files, and a step of calculating an exclusive OR of the partial files and the partial files excluding the partial files And a convolutional encryption program that causes a computer to execute.