JP2015045674A - Encryption system, encryption method and computer program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve safety for eavesdropping of data.SOLUTION: An encryption device generates block information including a block number for original data, a block length, a shuffle number and key information, and divides the original data by the block length corresponding to the block number in order of the block number, and encrypts each block, and rearranges and couples in order of the shuffle number, and generates encryption data. A decryption device generates the same block information as the encryption device, and divides the encryption data by the block length corresponding to the shuffle number in order of the shuffle number, and decrypts each block, and rearranges and couples in order of the block number, and restores the original data.

Description

  The present invention relates to a technology for data encryption and decryption.

  An encryption communication method is known in which transmission data is divided into a plurality of blocks, each block is encrypted with a different encryption key, and the encrypted block is transmitted (Patent Document 1).

JP-A-10-313306

  In the encrypted communication method of Patent Document 1, if an encrypted block is wiretapped during communication, the eavesdropper can know the data size of the encrypted block. The data size of the encrypted block can be one of hints for decrypting the encrypted block.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an encryption system, an encryption method, and a computer program that can conceal the data size of an encryption block and improve the security against eavesdropping of transmission data.

An encryption system according to an embodiment of the present invention includes an encryption device and a decryption device.
The encryption device
A block including a block number indicating each block when the original data is divided into a plurality of blocks, a block length corresponding to the block number, a shuffle number corresponding to the block number, and key information corresponding to the block number A block information generation unit for generating information;
A first dividing unit that divides the original data in the order of block numbers by a block length corresponding to the block number, and generates a plurality of blocks;
An encryption unit that encrypts each of the plurality of blocks using key information corresponding to the block number and generates a plurality of encrypted blocks;
Each of the plurality of encrypted blocks is rearranged in the order of the shuffle numbers and combined to have a first combining unit that generates encrypted data.
The decryption device
A block information generation unit that generates the same block information as the encryption device;
A second dividing unit that divides the encrypted data generated by the encryption device in the order of the shuffle numbers by a block length corresponding to the shuffle numbers, and generates a plurality of encrypted blocks;
A decryption unit that decrypts each of the plurality of encrypted blocks using key information corresponding to the shuffle number, and generates a plurality of decrypted blocks;
A second combining unit that recombines a plurality of decoded blocks in the order of the block numbers and restores the original data.

  According to the present invention, the data size of the encrypted block can be concealed, and the security against eavesdropping of transmission data can be improved.

2 shows an example of functional configurations of an encryption device and a decryption device included in an encryption system. An example of the information contained in shuffle information is shown. An example of the process in which an encryption apparatus produces | generates encryption data from original data is shown. An example of a process in which a decryption device generates original data from encrypted data is shown. It is a flowchart which shows an example of a process of an encryption apparatus and a decryption apparatus.

  Hereinafter, an embodiment of an encryption system capable of safely exchanging data between an encryption device and a decryption device against wiretapping will be described with reference to the drawings.

  FIG. 1 shows an example of the functional configuration of the encryption device 11 and the decryption device 12 included in the encryption system 1.

  The encryption system 1 includes an encryption device 11 and a decryption device 12. The encryption device 11 and the decryption device 12 transmit and receive data via the communication network 41.

  Each of the encryption device 11 and the decryption device 12 is a computer device including a CPU, a memory, a storage medium, a communication device (all not shown), and the like, and by executing a predetermined computer program on the CPU or the like, FIG. Implements various functions shown in.

  The memory is constituted by, for example, a DRAM (Dynamic Random Access Memory). The storage medium is configured by, for example, an HDD (Hard Disk Drive) or a flash memory. The communication device includes, for example, a device that supports Ethernet (registered trademark), wireless LAN (IEEE 802.11), 3G / LTE (Long Term Evolution), and the like. The communication network includes, for example, a wired / wireless LAN (Local Area Network), a WAN (Wide Area Network), an Internet network, or a combination thereof.

<Encryption device>
The encryption device 11 functions as a transmission / reception unit 28, a secret information management unit 21, a random number generation unit 22, a shuffle information generation unit 23, an encryption key generation unit 24, a first shuffle unit 25, and an encryption. Part 26 and first coupling part 27.

  The secret information management unit 21 holds the user information I and the secret information k, and manages the correspondence between the user information I and the secret information k. The user information I is information that can uniquely identify a user or a device. The secret information k is information for generating shuffle information 100, which will be described later, and an encryption / decryption key. The secret information k has a unique correspondence with the user information I. The secret information k is stored, for example, in a non-volatile memory having tamper resistance and is protected so as not to leak outside. When the user information I is input, the secret information management unit 21 provides the secret information k corresponding to the user information I to the shuffle information generation unit 23 and the encryption key generation unit 24.

  The random number generator 22 generates a random number r. The random number generation unit 22 provides the generated random number r to the shuffle information generation unit 23 and the encryption key generation unit 24. In addition, the random number generation unit 22 transmits the generated random number r to the decryption device 12. The random number generation unit 22 may generate a random number r triggered by receiving a data request from the decryption device 12. Alternatively, the random number generation unit 22 may generate a random number r using a request for a random number from the shuffle information generation unit 23 as a trigger.

  The shuffle information generation unit 23 generates the shuffle information 100. The shuffle information generation unit 23 determines the random number r provided from the random number generation unit 22, the secret information k provided from the secret information management unit 21, and the data length s of the original data to be transmitted to the decryption device 12. Substituting into the function f (r, k, s) in FIG. For example, in the function f, it is easy to calculate f (r, k, s) from r, k, s, but it is extremely difficult to estimate r, k, s from f (r, k, s). It is a one-way function. When the secret information k, the random number r, and the data length s are all the same, the same shuffle information 100 is generated. The shuffle information 100 is also stored in a non-volatile memory having tamper resistance, for example.

  FIG. 2 shows an example of information included in the shuffle information 100. Note that FIG. 2 shows the shuffle information 100 in a table format for convenience of explanation, but does not indicate that the shuffle information 100 is managed in this manner in the encryption apparatus 11.

  The shuffle information 100 includes information indicating the correspondence between the number of blocks, the block number 101, the offset 102, the block length 103, and the shuffle number 104.

  The number of blocks indicates how many blocks the original data is divided into. The number of blocks into which the original data is divided is determined by f (r, k, s). In the shuffle information 100 shown in FIG. 2, the maximum number of block numbers 101 corresponds to the number of blocks.

  The block number 101 is a number assigned in order from the first block when the original data is divided into a plurality of blocks. That is, when the plurality of divided blocks are combined in the order of the block numbers, the original data is restored.

  The offset 102 indicates the start position in the original data of the block indicated by the block number 101. The block length 103 indicates the length (data size) of the block indicated by the block number 101. The offset 102 and the block length 103 are specified in units of bytes, for example. In this embodiment, the block length 103 can be different for each block. However, all blocks may have the same block length 103. The length of each block is also determined by f (r, k, s).

  The shuffle number 104 indicates the order after shuffling of a plurality of blocks. The first combining unit 27 to be described later arranges the blocks in the order of the shuffle numbers 104 and combines them. The shuffle number for each block is also determined by f (r, k, s).

  For example, the row 110 in FIG. 2 is data obtained by extracting “200 bytes (block length)” from the beginning of the original data, starting with “250 bytes (offset)”, for the block having the block number 101 of “3”. This indicates that the order after shuffling is “first (shuffle number)”. Returning to the description of FIG.

  The encryption key generation unit 24 generates an encryption key. The encryption key generation unit 24 generates a different encryption key for each block. The encryption key generation unit 24 includes a random number r provided from the random number generation unit 22, k provided from the secret information management unit 21, and a block number i included in the shuffle information 100 generated in the shuffle information generation unit 23. Are substituted into a predetermined function g (r, k, i) to generate an encryption key. For example, the function g is easy to calculate g (r, k, i) from r, k, i, but it is extremely difficult to estimate r, k, i from g (r, k, i). It is a one-way function. When the random number r, the secret information k, and the block number i are all the same, the same encryption key is generated. The encryption key generation unit 24 provides the encryption key corresponding to the block number i to the encryption unit 26.

  The first shuffle unit 25 divides the original data into a plurality of blocks from the top in the order of the block number 101 included in the shuffle information 100 according to the offset 102 and the block length 103 corresponding to the block number 101. Then, the first shuffle unit 25 rearranges the plurality of blocks in the order of the shuffle numbers 104 included in the shuffle information 100.

  The encryption unit 26 encrypts each of the plurality of blocks divided by the first shuffle unit 25 with an encryption key corresponding to the block. That is, the encryption unit 26 encrypts the block with the block number i using the encryption key g (r, k, i). Hereinafter, the encrypted block is referred to as “encrypted block”.

  The first combining unit 27 combines a plurality of encrypted blocks divided and rearranged by the first shuffle unit 25 and encrypted by the encryption unit 26 in the order of the shuffle numbers 101 included in the shuffle information 100, and Generate data.

  The transmission / reception unit 28 transmits / receives various data to / from the decoding device 12 through the communication network 14. The user information I received by the transmission / reception unit 28 is provided to the secret information management unit 21. The transmission / reception unit 28 transmits the random number r to the decryption device 12. The transmission / reception unit 28 transmits the encrypted data to the decryption device 12.

FIG. 3 shows an example of a process in which the encryption device 11 generates encrypted data from original data.
(1) The first shuffle unit 25 reads original data from a predetermined storage medium.
(2) The first shuffle unit 25 sets the block length 103 in accordance with the offset 102 and the block length 103 corresponding to the block number 101 in the order of the block number 101 of the shuffle information 100 shown in FIG. Divide into different blocks 1, 2, 3, 4
(3) The first shuffle unit 25 rearranges the plurality of blocks 1, 2, 3, and 4 into block numbers 3, 2, 4, and 1 according to the order of the shuffle numbers 104 of the shuffle information 100 illustrated in FIG.
(4) The encryption unit 26 converts the blocks with block numbers 3, 2, 4, 1 into encryption keys g (r, k, 3), g (r, k, 2), g (r, k, 4), respectively. ), G (r, k, 1).
(5) The first combining unit 27 combines the encrypted blocks in the order of block numbers 3, 2, 4, and 1 in accordance with the order of the shuffle numbers 104 of the shuffle information 100 shown in FIG. 2, and generates encrypted data. .

  The above (3) and (4) may be interchanged. That is, (2) after dividing the original data, (3) encrypting blocks 1, 2, 3, and 4 using the encryption key, and (4) encrypting blocks 1, 2, 3, and 4 with the shuffle information 100 The blocks 3, 2, 4, and 1 may be rearranged in accordance with the shuffle number 104, and (5) may be combined. Returning to the description of FIG.

<Decryption device>
The decryption device 12 functions as a transmission / reception unit 38, a secret information management unit 31, a shuffle information generation unit 33, a decryption key generation unit 34, a second shuffle unit 35, a decryption unit 36, and a second And a coupling portion 37.

  The secret information management unit 31 basically has the same function as the secret information management unit 21 of the encryption device 11. The secret information management unit 21 of the encryption device 11 and the secret information management unit 31 of the decryption device 12 hold the same user information I and secret information k, and also correspond to the same user information I and secret information k. Manage.

  The secret information k may be stored in advance in the encryption device 11 and the decryption device 12 (for example, at the manufacturing stage), or may be acquired from a predetermined server via a secure communication path, and the encryption device 11 and It may be stored in the decryption device 12.

  The shuffle information generation unit 33 basically has the same functions and functions f (r, k, s) as the shuffle information generation unit 23 of the encryption device 11. The shuffle information generation unit 33 uses the random number r transmitted from the encryption device 11. The shuffle information generation unit 33 calculates the data length s from the data length of the encrypted data transmitted from the encryption device 11. Thereby, the shuffle information generation unit 33 can generate the same shuffle information 100 as that of the encryption device 11 using the function f (r, k, s).

  The decryption key generation unit 34 generates a decryption key. When the encryption key and the decryption key are common keys, the decryption key generation unit 34 basically has the same function and function g (r, k, i) as the encryption key generation unit 34. The decryption key generation unit 34 uses the random number r transmitted from the encryption device 11. Accordingly, the decryption key generation unit 34 can generate a decryption key for each encrypted block using the function g (r, k, i).

  The second shuffle unit 35 divides the encrypted data into a plurality of encrypted blocks from the top in the order of the shuffle numbers 104 included in the shuffle information 100 according to the offset 101 and the data length 102 corresponding to the shuffle numbers 104. Then, the second shuffle unit 35 rearranges the plurality of encrypted blocks in the order of the block numbers 101 included in the shuffle information 100.

  The decryption unit 36 decrypts each of the plurality of encrypted blocks divided by the second shuffle unit 35 with a decryption key corresponding to the block. That is, the decryption unit 36 decrypts the block with the block number i using the decryption key g (r, k, i).

  The second combining unit 37 is divided by the second shuffle unit 35, rearranged in the order of the block number 101 (original order), and has a plurality of blocks decoded by the decoding unit 36 in the shuffle information 100. The original data is generated by combining them in the order of the block numbers 101.

  The transmission / reception unit 38 transmits / receives various data to / from the encryption device 11 through the communication network 14. The transmission / reception unit 38 transmits the user information I and the data request to the encryption device 11. The encrypted data received by the transmission / reception unit 38 is provided to the second shuffle unit 35.

FIG. 4 shows an example of a process in which the decryption device 12 generates original data from encrypted data.
(1) The second shuffle unit 35 receives the encrypted data through the transmission / reception unit 39.
(2) The second shuffle unit 35, in the order of the shuffle number 101 of the shuffle information 100 shown in FIG. It is divided into a plurality of different encrypted blocks 3, 2, 4, 1.
(3) The second shuffle unit 35 arranges the plurality of encrypted blocks 3, 2, 4, 1 in block numbers 1, 2, 3, 4 according to the order of the block numbers 101 of the shuffle information 100 shown in FIG. Change.
(4) The decryption unit 36 decrypts the encrypted blocks of block numbers 1, 2, 3, and 4 with decryption keys g (r, k, 1), g (r, k, 2), and g (r, k , 3) and g (r, k, 4).
(5) The second combining unit 37 combines the blocks in the order of block numbers 1, 2, 3, and 4 according to the order of the block numbers 101 of the shuffle information 100 shown in FIG.

  The above (3) and (4) may be interchanged. That is, (2) after dividing the encrypted data, (3) decrypting the blocks 3, 2, 4, 1 using the decryption key, and (4) shuffle the blocks 3, 2, 4, 1 into the shuffle information The blocks may be rearranged in the order of blocks 1, 2, 3, and 4 according to the block number (5) and then combined.

  FIG. 5 is a flowchart illustrating an example of processing of the encryption device 11 and the decryption device 12.

  The decryption device 12 transmits a data request and user information I to the encryption device 11 (S10). User information I may be included in the data request.

  The encryption device 11 that has received the data request generates a random number r and transmits the random number r to the decryption device 12 (S11).

  Then, the encryption device 11 uses the generated random number r, the secret information k corresponding to the user information I received from the decryption device 12, and the data length s of the original data to be transmitted to the decryption device 12. Then, the shuffle information f (r, k, s) is generated (S12).

  The encryption device 11 divides the original data in the order of the block number 101 of the generated shuffle information 100 according to the offset 102 and the data length 103 corresponding to the block number 101, and generates a plurality of blocks (S13). .

  The encryption device 11 rearranges the plurality of blocks in the order of the shuffle number 104 of the shuffle information 100 (S14).

The encryption device 11 generates a different encryption key g (r, k, i) for each block number 101 (S15).
The encryption device 11 encrypts the block corresponding to the block number 101 using the encryption key g (r, k, i) corresponding to the block number 101 (S16).

The encryption device 11 combines the plurality of encrypted blocks in the order of the shuffle number 101 of the shuffle information 100 to generate encrypted data (S17).
The encryption device 11 transmits the encrypted data to the decryption device 12 (S18).

  The decryption device 12 that has received the encrypted data receives the random number r received from the encryption device 11, the secret information k corresponding to the user information I transmitted to the encryption device 11, and the encryption received from the encryption device 11. The data length s of the data is substituted into the function f (r, k, s) to generate the shuffle information 100 (S22). The shuffle information 100 is the same as the shuffle information 100 generated by the encryption device 11.

  The decryption device 12 divides the encrypted data in the order of the shuffle number 104 of the generated shuffle information 100 according to the offset 102 and the data length 103 corresponding to the shuffle number 104, and generates a plurality of encrypted blocks. (S23).

  The decryption device 12 rearranges the plurality of encrypted blocks in the order of the block number 101 of the shuffle information 100 (original order) (S24).

  The decryption device 12 generates a different decryption key g (r, k, i) for each block number 101 (S25). When the encryption key and the decryption key are common keys, the decryption key is the same as the encryption key generated by the encryption device 11.

  The decryption device 12 decrypts the block corresponding to the block number 101 using the decryption key g (r, k, i) corresponding to the block number 101 (S26).

  The decryption device 12 combines the plurality of combined blocks in the order of the block number 101 of the shuffle information 100 to generate original data (S27).

  Through the above processing, the encryption device 11 can securely transmit the original data to the decryption device 12. And according to the above-mentioned composition, a possibility that encryption data may be deciphered by a third party (the eavesdropper) can be further reduced. Because encrypted data is composed of encrypted blocks with different block lengths, even if a third party tries to decrypt the encrypted data, the third party can guess the division position of the encrypted data. It is not possible. Furthermore, the block length is different, the order of the blocks is rearranged, and the fact that each block is encrypted with a different encryption key also makes it difficult for a third party to decrypt the encrypted data. In addition, since information regarding the block number is not included in the block, it becomes more difficult to decrypt the encrypted data of a third party.

<Modification>
The embodiment described above may be modified as follows.

(1) In the above description, the encryption device 11 and the decryption device 12 each independently generate shuffle information 100. However, the encryption device 11 may encrypt the generated shuffle information 100 and transmit it to the decryption device 12 together with the encrypted data. Then, the decryption device 12 may convert the encrypted data into the original data using the shuffle information 100 transmitted from the encryption device 11. This eliminates the need for the decoding device 12 to generate the shuffle information 100 by itself. That is, the processing load on the decoding device 12 is reduced.

(2) The encryption device 11 has a function of outputting the encrypted data to an external storage medium (such as a USB memory or an SD card), and the decryption device 12 reads the encrypted data from the external storage medium, It may have a function of generating original data. In this case, for example, the encryption device 11 outputs its own user information I and the generated random number r together with the encrypted data to an external storage medium. Then, the decryption device 12 converts the encrypted data into the original data using the user information I and the random number r stored in the external storage medium.

(3) In the configuration of (2) above, the encryption device 11 may encrypt the generated shuffle information 100 and output it together with the encrypted data to an external storage medium. Then, the decryption device 12 may convert the encrypted data into the original data using the shuffle information 100 read from the external storage medium.

(4) In the configuration of (2) or (3) above, when the encryption device 11 generates a plurality of encrypted data using one random number r, the one random number r and the plurality of encrypted data May be collectively output to an external storage medium. Then, the decryption device 12 may convert a plurality of encrypted data into original data using one random number r read from the external storage medium.

(5) The common key used as the encryption key and the decryption key may be generated using an encryption algorithm such as AES (Advanced Encryption Standard), Triple DES (Data Encryption Standard), or RC4.

(6) The encryption key and the decryption key may not be a common key, but one of them may be a “secret key” and the other a “public key”.

  The above-described embodiments of the present invention are examples for explaining the present invention, and are not intended to limit the scope of the present invention only to those embodiments. Those skilled in the art can implement the present invention in various other modes without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Encryption system 11 ... Encryption apparatus 12 ... Decryption apparatus

Claims (6)

An encryption system comprising an encryption device and a decryption device,
The encryption device
A block number indicating each block when the original data is divided into a plurality of blocks, a block length corresponding to the block number, a shuffle number corresponding to the block number, and key information corresponding to the block number; A block information generation unit that generates block information including:
A first dividing unit that divides the original data in block number order by a block length corresponding to the block number, and generates a plurality of blocks;
An encryption unit that encrypts each of the plurality of blocks using key information corresponding to the block number, and generates a plurality of encrypted blocks;
A plurality of encrypted blocks that are rearranged in the order of shuffle numbers and combined to generate encrypted data;
The decryption device
A block information generation unit that generates the same block information as the encryption device;
A second dividing unit that divides the encrypted data generated by the encryption device in the order of shuffle numbers by a block length corresponding to the shuffle numbers, and generates a plurality of encrypted blocks;
A decryption unit that decrypts each of the plurality of encrypted blocks using key information corresponding to the shuffle number, and generates a plurality of decrypted blocks;
And a second combining unit that combines the plurality of decrypted blocks in the order of block numbers and restores the original data.
The number of divisions of the original data, the block length corresponding to the block number, and the shuffle number corresponding to the block number are predetermined secret information, a random number corresponding to the original data, and the original data The encryption system according to claim 1, wherein the encryption system is uniquely determined based on the data length.
The encryption device transmits a random number corresponding to the original data to the decryption device;
The encryption system according to claim 2, wherein the block information generation unit in the decryption device generates block information corresponding to the original data using a random number corresponding to the original data received from the encryption device. .
The encryption device writes a random number corresponding to the original data and the encrypted data generated in the first combining unit to an external storage medium,
3. The encryption system according to claim 2, wherein the block information generation unit in the decryption device generates block information corresponding to the original data using a random number corresponding to the original data read from the external storage medium. .
A data encryption method,
In the encryption device,
A block number indicating each block when the original data is divided into a plurality of blocks, a block length corresponding to the block number, a shuffle number corresponding to the block number, and key information corresponding to the block number; Generate block information including
The original data is divided in block number order by a block length corresponding to the block number to generate a plurality of blocks,
Each of the plurality of blocks is encrypted using key information corresponding to the block number to generate a plurality of encrypted blocks,
Reordering and combining the plurality of encrypted blocks in the order of shuffle numbers to generate encrypted data;
In the decryption device,
Generate the same block information as the encryption device,
The encrypted data generated by the encryption device is divided in the order of shuffle numbers, with a block length corresponding to the shuffle numbers, to generate a plurality of encrypted blocks,
Each of the plurality of encrypted blocks is decrypted using the key information corresponding to the shuffle number to generate a plurality of decrypted blocks,
A data encryption method in which the plurality of decryption blocks are rearranged and combined in the order of block numbers to restore the original data.
A computer program for data encryption,
When executed on the encryption device:
A block number indicating each block when the original data is divided into a plurality of blocks, a block length corresponding to the block number, a shuffle number corresponding to the block number, and key information corresponding to the block number; Generate block information including
The original data is divided in the order indicated by the block number by the block length corresponding to the block number, to generate a plurality of blocks,
Each of the plurality of blocks is encrypted using key information corresponding to the block number to generate a plurality of encrypted blocks,
Reordering and combining each of the plurality of encrypted blocks in the order of shuffle numbers to generate encrypted data;
When executed in the decryption device,
Generate the same block information as the encryption device,
The encrypted data generated by the encryption device is divided in the order of shuffle numbers, with a block length corresponding to the shuffle numbers, to generate a plurality of encrypted blocks,
Each of the plurality of encrypted blocks is decrypted using the key information corresponding to the shuffle number to generate a plurality of decrypted blocks,
A computer program that restores the original data by rearranging and combining the plurality of decoded blocks in the order of block numbers.

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