JP7063628B2 - Cryptographic devices, encryption methods and programs - Google Patents

Description

The present invention relates to an encryption device, a decryption device, a line encryption system, an encryption method and a program. In particular, the present invention relates to an encryption device using a block cipher, a decryption device, a line encryption system, an encryption method and a program.

With the development of the information-oriented society, the risk of information leakage and falsification is increasing. Information security technology is important to ensure the security and reliability of information. Encryption technology is one of the elements that make up information security technology. Encryption technology is used in various products regardless of hardware or software.

Encryption technology is roughly divided into two methods, a public key cryptosystem and a common key cryptosystem. In public key cryptography, two types of keys are used: a public key that can be obtained by anyone and a private key that is held only by the receiving side. The public key cryptosystem is characterized by easy key transfer. On the other hand, in the common key cryptosystem, the same key called a common key is used. The common key cryptosystem is characterized by its fast processing due to its simple mechanism.

When the common key cryptosystem is classified by the type of cryptographic algorithm, it can be divided into two types: stream cipher and block cipher. Stream cipher is a cryptographic algorithm that performs processing in small units such as 1 byte. On the other hand, the block cipher is a cryptographic algorithm that divides the unit of encryption processing into a group called a block and performs processing. The block cipher has a structure that performs iterative processing called a round. In the block cipher, the key schedule unit generates a subkey to be used in each round, and the data scramble unit uses each subkey to convert plaintext into ciphertext. Block ciphers are suitable for encrypting large amounts of data.

Patent Document 1 discloses a cryptographic processing apparatus that executes common key block cipher processing. The apparatus of Patent Document 1 has a cryptographic processing unit that performs data conversion processing that repeats a round function for a plurality of rounds, and a key schedule unit that generates a round key to be applied to the execution of the round function. The key schedule unit inputs an intermediate key generator that generates an intermediate key by inputting a private key into an encryption function including a round function used in the encryption processing unit, and an intermediate key generator that generates an intermediate key. It has an intermediate key expansion unit that generates a key.

As one of the block cipher methods, there is a method of limiting the number of times a subkey is generated in order to encrypt a large amount of data at high speed. For example, the processing of the key schedule unit is performed only in the first block, and the subkey generated by the key schedule unit is stored in a storage unit such as a register or a memory. In the second and subsequent encryption blocks, plaintext is encrypted using the subkey stored in the storage unit. When this method is used, not only the common key but also the subkey is managed in order to perform the encryption process safely.

Japanese Unexamined Patent Publication No. 2008-058831

In the block encryption processing of the general common key encryption method, the common key is stored in the storage unit and the key schedule is executed each time the encryption processing is performed. There was a problem that it was hung.

Further, the device of Patent Document 1 can increase the difficulty of key analysis by using a plurality of types of keys such as a private key, an intermediate key, and a round key when encrypting plaintext. However, the device of Patent Document 1 has a problem that key management becomes complicated.

Further, according to the method of limiting the number of times of subkey generation, a large amount of data can be encrypted at high speed. However, in the case of this method, in addition to the common key, the subkey generated by the key schedule is also stored in the storage unit, so that there is a problem that the risk of key leakage or falsification increases.

An object of the present invention is to provide an encryption device capable of securely and high-speed encryption of a large amount of data without affecting the processing performance in order to solve the above-mentioned problems.

In the encryption device of one aspect of the present invention, at least one subkey from the first common key holder holding the first common key and the first common key held in the first common key holder is key-scheduled. A common key that acquires a subkey generator to generate, a subkey holder that holds the subkey generated by the subkey generator, and a subkey held by the subkey holder to decrypt the second common key. The decryption unit, the second common key holder that holds the second common key decrypted by the common key decryption unit, the first common key held by the first common key holder, and the second common key holder. A common key comparison unit that compares the held second common key, an encryption unit that encrypts a plain text block using the sub key held in the sub key holder, and generates an encryption block, and a common key comparison. Whether or not the comparison result between the first common key and the second common key by the unit and the encryption text block generated by the encryption unit are input and the encryption text block is output based on the comparison result by the common key comparison unit. It is provided with an output determination unit for determining whether or not.

The decryption device of one aspect of the present invention generates at least one subkey from the first common key holding unit holding the first common key and the first common key held in the first common key holding unit by a key schedule. Sub-key generation unit, sub-key holding unit that holds the sub-key generated by the sub-key generation unit, and common key decryption that acquires the sub-key held in the sub-key holding unit and decrypts the second common key. A unit, a second common key holding unit that holds the second common key decrypted by the common key decrypting unit, a first common key held in the first common key holding unit, and a second common key holding unit. A common key comparison unit that compares the second common key that has been created, a decryption unit that decrypts a plain text block from a cryptographic text block using the subkey held in the subkey holding unit, and a first common key comparison unit. An output determination unit that inputs the comparison result between the key and the second common key and the plain text block decoded by the decoding unit, and determines whether or not to output the plain text block based on the comparison result by the common key comparison unit. To prepare for.

The line encryption system of one aspect of the present invention generates at least one subkey from the first common key in a key schedule, encrypts a plain text block using the generated subkey, and generates a cryptographic block. An encryption device that decrypts the second common key using the generated subkey and determines whether to output a ciphertext block based on the comparison result between the first common key and the second common key. At least one subkey is generated from the first common key in the key schedule, the plain text block is decrypted from the ciphertext block using the generated subkey, and the second common key is decrypted using the generated subkey. Then, the encryption device is provided with a decryption device that determines whether or not to output the plain text block based on the comparison result between the first common key and the second common key, and the encryption device is an encrypted text block in which the plain text block is encrypted. Is transmitted to the decryption device, and the decryption device decrypts the plain text block from the ciphertext block received from the encryption device.

In the encryption method of one aspect of the present invention, the first common key is held in the first common key holding unit, and at least one subkey from the first common key held in the first common key holding unit is key-scheduled. The generated subkey is held in the subkey holder, the second common key is decrypted using the subkey held in the subkey holder, and the decrypted second common key is used in the second common. The first common key held in the key holding unit and held in the first common key holding unit is compared with the second common key held in the second common key holding unit, and held in the sub key holding unit. The plain text block is encrypted using the sub key to generate the cipher text block, and it is determined whether or not to output the cipher text block based on the comparison result between the first common key and the second common key.

In the program of one aspect of the present invention, the process of holding the first common key in the first common key holder and at least one subkey from the first common key held in the first common key holder are key-scheduled. The process of generating, the process of holding the generated subkey in the subkey holder, the process of decrypting the second common key using the subkey held in the subkey holder, and the process of decrypting the second common The process of holding the key in the second common key holder and the process of comparing the first common key held in the first common key holder with the second common key held in the second common key holder. , The process of encrypting a plain text block using the sub key held in the sub key holder to generate a cryptographic block, and outputting the cipher block based on the comparison result between the first common key and the second common key. A program that causes a computer to execute a process that determines whether or not to do so.

According to the present invention, it is possible to provide an encryption device capable of securely and at high speed encrypting a large amount of data without affecting the processing performance.

It is a block diagram which shows an example of the structure of the encryption apparatus which concerns on 1st Embodiment of this invention. It is a flowchart for demonstrating the operation example of the encryption apparatus which concerns on 1st Embodiment of this invention. It is a block diagram which shows an example of the structure of the encryption apparatus which concerns on 2nd Embodiment of this invention. It is a flowchart for demonstrating the operation example of the encryption apparatus which concerns on 2nd Embodiment of this invention. It is a block diagram which shows an example of the structure of the encryption apparatus which concerns on 3rd Embodiment of this invention. It is a flowchart for demonstrating the operation example of the encryption apparatus which concerns on 3rd Embodiment of this invention. It is a block diagram which shows an example of the structure of the encryption apparatus which concerns on 4th Embodiment of this invention. It is a flowchart for demonstrating the operation example of the encryption apparatus which concerns on 4th Embodiment of this invention. It is a block diagram which shows an example of the structure of the encryption apparatus which concerns on 5th Embodiment of this invention. It is a flowchart for demonstrating the operation example of the encryption apparatus which concerns on 5th Embodiment of this invention. It is a block diagram which shows an example of the structure of the decoding apparatus which concerns on 6th Embodiment of this invention. It is a block diagram which shows an example of the structure of the line encryption system which concerns on 7th Embodiment of this invention. It is a block diagram which shows the hardware configuration example of the encryption apparatus and the decryption apparatus which concerns on each embodiment of this invention.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, although the embodiments described below have technically preferable limitations for carrying out the present invention, the scope of the invention is not limited to the following. Further, in all the drawings used in the following embodiments, the same reference numerals are given to the same parts unless there is a specific reason. Further, in the following embodiments, repeated explanations may be omitted for similar configurations and operations. Further, the direction of the arrow in the drawing shows an example and does not limit the direction of the signal.

(First Embodiment)
First, the encryption device according to the first embodiment of the present invention will be described with reference to the drawings. In the encryption device of the present embodiment, at least one plaintext block constituting the encryption target data (also referred to as target data) and a common key for encrypting the plaintext block are input. The encryption device of the present embodiment generates a ciphertext block by generating a subkey from a common key and encrypting the plaintext block using the generated subkey. The encryption device of the present embodiment may be configured to encrypt a plaintext block into an encryption block using a common key stored in advance.

(Constitution)
FIG. 1 is a block diagram showing an example of the configuration of the encryption device 1 of the present embodiment. As shown in FIG. 1, the encryption device 1 includes a first common key holding unit 11, a key schedule unit 12, a sub key holding unit 13, a common key decryption unit 14, a second common key holding unit 15, and a common key comparison unit 16. , A data scramble unit 17, and an output determination unit 18.

The first common key holding unit 11 (also referred to as a first common key holding means) holds an input common key (hereinafter, also referred to as a first common key). For example, the first common key holding unit 11 is realized by a register or a memory.

The key schedule unit 12 (also referred to as a sub-key generation means) acquires the first common key held by the first common key holding unit 11. The key schedule unit 12 generates a subkey from the acquired first common key. For example, the key schedule unit 12 generates N subkeys used in all rounds from the first common key (N is a natural number). The key schedule unit 12 stores the generated subkey in the subkey holding unit 13.

For example, the key schedule unit 12 performs a key schedule using a block cipher algorithm of a common key method such as AES (Advanced Encryption Standard). The key schedule unit 12 may perform a key schedule using a block encryption algorithm such as DES (Data Encryption Standard) or triple DES. Further, the key schedule unit 12 may perform a key schedule using a block cipher algorithm such as MISTY1 (Mitsubishi Improved Security Technology) or Camelia. However, the key schedule by the key schedule unit 12 is not limited to the method described here.

The sub-key holding unit 13 (also referred to as a sub-key holding means) stores the sub-key generated by the key schedule unit 12. For example, the sub-key holding unit 13 is realized by a register or a memory.

The common key decryption unit 14 (also referred to as a common key decryption means) decodes a common key (hereinafter, also referred to as a second common key) from the subkey stored in the subkey holding unit 13. For example, the common key decryption unit 14 decodes the second common key from the N subkeys stored in the subkey holding unit 13 (N is a natural number). The common key decryption unit 14 causes the second common key holding unit 15 to hold the decrypted second common key.

The second common key holding unit 15 (also referred to as a second common key holding means) holds the second common key decrypted by the common key decoding unit 14. For example, the second common key holding unit 15 is realized by a register or a memory.

The common key comparison unit 16 (also referred to as a common key comparison means) compares the first common key held in the first common key holding unit 11 with the second common key held in the second common key holding unit 15. do. The common key comparison unit 16 outputs the comparison result of the first common key and the second common key to the output determination unit 18.

At least one plaintext block constituting the encryption target data (also referred to as target data) is input to the data scramble unit 17 (also referred to as encryption means), and the sub key is input from the sub key holding unit 13. The data scramble unit 17 generates a ciphertext block by encrypting the input plaintext block using the subkey. The data scramble unit 17 outputs the generated ciphertext block to the output determination unit 18.

A ciphertext block is input from the data scramble unit 17 to the output determination unit 18 (also referred to as an output determination means), and a comparison result between the first common key and the second common key is input from the common key comparison unit 16. The output determination unit 18 determines whether or not to output the ciphertext block based on the comparison result by the common key comparison unit 16. The output determination unit 18 determines that the ciphertext block is output when the first common key and the second common key are the same. On the other hand, when the first common key and the second common key are different, the output determination unit 18 detects an abnormality (also called an error) such as a failure or tampering in the subkey, and discards the ciphertext block without outputting it. ..

The above is the description of the configuration of the encryption device 1. Next, the operation of the encryption device 1 will be described with reference to the drawings.

(motion)
FIG. 2 is a flowchart for explaining an example of the operation of the encryption device 1. That is, FIG. 2 is a flowchart showing the procedure of the encryption process executed by the encryption device 1. In the description according to the flowchart of FIG. 2 below, the encryption device 1 will be described as the main body of operation.

In FIG. 2, first, when a common key is input, the encryption device 1 stores the common key (also referred to as a first common key) in the first common key holding unit 11 (step S101).

Next, the encryption device 1 generates a subkey from the first common key stored in the first common key holding unit 11 by performing a key schedule by a block encryption algorithm of a common key method (step S102).

Next, the encryption device 1 stores the generated subkey in the subkey holding unit 13 (step S103).

The encryption device 1 uses the subkey stored in the subkey holding unit 13 to encrypt the input plaintext block by the block cipher algorithm of the common key method (step S104).

Further, the encryption device 1 executes a common key decryption process using the subkey stored in the subkey holding unit 13 in parallel with the encryption process in step S104, and performs a common key decryption process (also referred to as a second common key). ) Is decoded (step S105).

Next, the encryption device 1 stores the decrypted second common key in the second common key holding unit 15 (step S106).

Next, the encryption device 1 compares the first common key stored in the first common key holding unit 11 with the second common key stored in the second common key holding unit 15 (step S107).

Then, when the first common key and the second common key match (Yes in step S108), the encryption device 1 outputs a ciphertext block (step S109).

On the other hand, when the first common key and the second common key do not match (No in step S108), the encryption device 1 detects an abnormality in the subkey, performs error processing, and discards the ciphertext block. (Step S110).

The above is an explanation of an example of the operation of the encryption device 1 according to the flowchart of FIG.

As described above, the encryption device of the present embodiment has the input common key (first common key) and the common key decrypted from the subkey (second common key) in parallel with the data encryption process. And, and determine whether or not there is an abnormality in the common key or subkey. Further, the encryption device of the present embodiment determines whether or not to output the ciphertext block based on the determination result regarding the presence or absence of an abnormality in the common key or the subkey. The encryption device of the present embodiment does not output an invalid ciphertext block by performing error processing when there is an abnormality in the common key or the subkey.

That is, according to the encryption device of the present embodiment, a large amount of data can be encrypted safely and at high speed without affecting the processing performance.

(Second embodiment)
Next, the encryption device according to the second embodiment of the present invention will be described with reference to the drawings. The encryption device of the present embodiment is different from the first embodiment in that it determines whether or not to generate a subkey based on the presence or absence of a subkey corresponding to the input common key. In the following description, the same reference numerals may be given to the same configurations as those in the first embodiment, and detailed description may be omitted.

FIG. 3 is a block diagram showing an example of the configuration of the encryption device 2 of the present embodiment. As shown in FIG. 3, the encryption device 2 has a configuration in which the sub-key generation determination unit 21 is added to the encryption device 1 of the first embodiment.

A common key is input to the sub-key generation determination unit 21 (also referred to as a sub-key generation determination means). The sub-key generation determination unit 21 determines whether or not the input common key is equal to the first common key held in the first common key holding unit 11. In other words, the sub-key generation determination unit 21 determines whether or not the input common key is different from the current common key.

The sub-key generation determination unit 21 does not allow the key schedule unit 12 to execute the key schedule if the input common key has not changed. On the other hand, when the input common key has changed, the sub-key generation determination unit 21 causes the first common key holding unit 11 to hold the new common key as the first common key, and the key schedule unit 12 holds the key schedule. Let it run.

The key schedule unit 12 executes the key schedule according to the determination result of the sub key generation determination unit 21. That is, if the sub-key generation determination unit 21 determines that the common key has not changed, the key schedule unit 12 does not execute the key schedule. On the other hand, when the sub-key generation determination unit 21 determines that the common key has changed, the key schedule unit 12 executes the key schedule for the new common key held by the first common key holding unit 11.

Since other configurations are the same as those of the encryption device 1 of the first embodiment, detailed description thereof will be omitted.

The above is an explanation of an example of the configuration of the encryption device 2. Next, an example of the operation of the encryption device 2 will be described with reference to the drawings.

(motion)
FIG. 4 is a flowchart for explaining an example of the operation of the encryption device 2. That is, FIG. 4 is a flowchart showing the procedure of the encryption process executed by the encryption device 2. In the description according to the flowchart of FIG. 4 below, the encryption device 2 will be described as the main body of operation.

In FIG. 4, first, when the common key is input, the encryption device 2 determines whether or not the subkey of the common key has been generated (step S201).

If the subkey has already been generated (Yes in step S201), the process proceeds to step S205 and step S206. On the other hand, when the subkey has not been generated (No in step S201), the encryption device 2 stores the input common key as the first common key in the first common key holding unit 11 (step S202).

Next, the encryption device 2 generates a subkey from the first common key stored in the first common key holding unit 11 by performing a key schedule by a block encryption algorithm of a common key method (step S203).

Next, the encryption device 2 stores the generated subkey in the subkey holding unit 13 (step S204).

The encryption device 2 uses the subkey stored in the subkey holding unit 13 to encrypt the input plaintext block by the block cipher algorithm of the common key method (step S205).

Further, the encryption device 2 executes a common key decryption process using the subkey stored in the subkey holding unit 13 in parallel with the encryption process in step S205, and performs a common key decryption process (also referred to as a second common key). ) Is decoded (step S206).

Next, the encryption device 2 stores the second common key in the second common key holding unit 15 (step S207).

Next, the encryption device 2 compares the first common key stored in the first common key holding unit 11 with the second common key stored in the second common key holding unit 15 (step S208).

Then, when the first common key and the second common key match (Yes in step S209), the encryption device 2 outputs a ciphertext block (step S210).

On the other hand, when the first common key and the second common key do not match (No in step S209), the encryption device 2 detects an abnormality in the subkey, performs error processing, and discards the ciphertext block. (Step S211).

The above is an explanation of an example of the operation of the encryption device 2 according to the flowchart of FIG.

As described above, when the subkey has been generated from the input common key, the encryption device of the present embodiment executes the encryption process using the generated subkey. Therefore, according to the encryption device of the present embodiment, the key schedule processing can be omitted as long as the common key does not change.

(Third embodiment)
Next, the encryption device according to the third embodiment of the present invention will be described with reference to the drawings. The encryption device of the present embodiment is different from the first embodiment in that a common key is generated in response to an encryption instruction instead of inputting a common key. In the following description, the same reference numerals may be given to the same configurations as those in the first embodiment, and detailed description may be omitted.

FIG. 5 is a block diagram showing an example of the configuration of the encryption device 3 of the present embodiment. As shown in FIG. 5, the encryption device 3 has a configuration in which a pseudo-random number generation unit 31 and a common key generation unit 32 are added to the encryption device 1 of the first embodiment.

An encryption instruction is input to the pseudo-random number generation unit 31 (also referred to as a pseudo-random number generation means). The pseudo-random number generation unit 31 generates a pseudo-random number according to the encryption instruction. The pseudo-random number generation unit 31 outputs the generated pseudo-random number to the common key generation unit 32. It should be noted that the pseudo-random number generation unit 31 may be configured to generate a pseudo-random number at the timing when the plaintext block is input.

A pseudo-random number generated by the pseudo-random number generation unit 31 is input to the common key generation unit 32 (also referred to as a common key generation means). The common key generation unit 32 generates a common key using the input pseudo-random number. The common key generation unit 32 stores the generated common key as the first common key in the first common key holding unit 11.

Since other configurations are the same as those of the encryption device 1 of the first embodiment, detailed description thereof will be omitted.

The above is an explanation of an example of the configuration of the encryption device 3. Next, an example of the operation of the encryption device 3 will be described with reference to the drawings.

(motion)
FIG. 6 is a flowchart for explaining an example of the operation of the encryption device 3. That is, FIG. 6 is a flowchart showing the procedure of the encryption process executed by the encryption device 3. In the description according to the flowchart of FIG. 6 below, the encryption device 3 will be described as the main body of operation.

In FIG. 6, first, the encryption device 3 generates a pseudo-random number when an encryption instruction is input (step S301).

Next, the encryption device 3 generates a common key using the generated pseudo-random number (step S302).

Next, the encryption device 3 stores the generated common key (also referred to as the first common key) in the first common key holding unit 11 (step S303).

Next, the encryption device 3 generates a subkey from the first common key stored in the first common key holding unit 11 by performing a key schedule by a block encryption algorithm of a common key method (step S304).

Next, the encryption device 3 stores the generated subkey in the subkey holding unit 13 (step S305).

The encryption device 3 uses the subkey stored in the subkey holding unit 13 to encrypt the input plaintext block by the block cipher algorithm of the common key method (step S306).

Further, the encryption device 3 executes a common key decryption process using the subkey stored in the subkey holding unit 13 in parallel with the encryption process in step S306, and performs a common key decryption process (also referred to as a second common key). ) Is decoded (step S307).

Next, the encryption device 3 stores the second common key in the second common key holding unit 15 (step S308).

Next, the encryption device 3 compares the first common key stored in the first common key holding unit 11 with the second common key stored in the second common key holding unit 15 (step S309).

Then, when the first common key and the second common key match (Yes in step S310), the encryption device 3 outputs a ciphertext block (step S311).

On the other hand, when the first common key and the second common key do not match (No in step S310), the encryption device 3 detects an abnormality in the subkey, performs error processing, and discards the ciphertext block. (Step S312).

The above is an explanation of an example of the operation of the encryption device 3 according to the flowchart of FIG.

As described above, the encryption device of the present embodiment generates a common key in response to the encryption instruction. Therefore, according to the encryption device of the present embodiment, since the common key acquired from the outside is not used, the encryption is not performed by using the common key which may be leaked or tampered with, and the security of the ciphertext block is prevented. And reliability is improved.

(Fourth Embodiment)
Next, the encryption device according to the fourth embodiment of the present invention will be described with reference to the drawings. The first embodiment of the encryption device of the present embodiment is that when an abnormality is suspected in the subkey based on the comparison result of the common key, the subkey is recreated from the first common key and re-encrypted. It is different from the form. In the following description, the same reference numerals may be given to the same configurations as those in the first embodiment, and detailed description may be omitted.

FIG. 7 is a block diagram showing an example of the configuration of the encryption device 4 of the present embodiment. As shown in FIG. 7, the encryption device 4 has a configuration in which a retry determination unit 41 is added to the encryption device 1 of the first embodiment.

A comparison result between the first common key and the second common key by the common key comparison unit 16 is input to the retry determination unit 41 (retry determination means). When the retry determination unit 41 suspects that there is an abnormality in the subkey based on the comparison result between the first common key and the second common key, the retry determination unit 41 recycles the subkey from the first common key to the key schedule unit 12. Give instructions to create.

The key schedule unit 12 executes a key schedule using the first common key stored in the first common key holding unit 11 in response to an instruction from the retry determination unit 41, and recreates the subkey. The key schedule unit 12 stores the recreated subkey in the subkey holding unit 13.

Since other configurations are the same as those of the encryption device 1 of the first embodiment, detailed description thereof will be omitted.

The above is an explanation of an example of the configuration of the encryption device 4. Next, an example of the operation of the encryption device 4 will be described with reference to the drawings.

(motion)
FIG. 8 is a flowchart for explaining an example of the operation of the encryption device 4. That is, FIG. 8 is a flowchart showing the procedure of the encryption process executed by the encryption device 4. In the description according to the flowchart of FIG. 8 below, the encryption device 4 will be described as the main body of operation.

In FIG. 8, first, when the common key is input, the encryption device 4 stores the common key (also referred to as the first common key) in the first common key holding unit 11 (step S401).

Next, the encryption device 4 generates a subkey from the first common key stored in the first common key holding unit 11 by performing a key schedule by a block encryption algorithm of a common key method (step S402).

Next, the encryption device 4 stores the generated subkey in the subkey holding unit 13 (step S403).

The encryption device 4 uses the subkey stored in the subkey holding unit 13 to encrypt the input plaintext block by the block cipher algorithm of the common key method (step S404).

Further, the encryption device 4 executes a common key decryption process using the subkey stored in the subkey holding unit 13 in parallel with the encryption process in step S404, and performs a common key decryption process (also referred to as a second common key). ) Is decoded (step S405).

Next, the encryption device 4 stores the decrypted second common key in the second common key holding unit 15 (step S406).

Next, the encryption device 4 compares the first common key stored in the first common key holding unit 11 with the second common key stored in the second common key holding unit 15 (step S407).

Then, when the first common key and the second common key match (Yes in step S408), the encryption device 4 determines that there is no abnormality in the subkey and outputs a ciphertext block (step S409).

On the other hand, when the first common key and the second common key do not match (No in step S408), the encryption device 4 determines that the subkey has an abnormality. At this time, returning to step S402, the encryption device 4 re-executes the key schedule processing to generate a new subkey from the first common key stored in the first common key holding unit 11.

The above is an explanation of an example of the operation of the encryption device 4 according to the flowchart of FIG.

As described above, when the subkey is suspected of being leaked or tampered with, the encryption device of the present embodiment recreates the subkey using the first common key stored in the first common key holding unit. Then, the encryption device of the present embodiment performs encryption using the recreated subkey. Therefore, according to the encryption device of the present embodiment, it is possible to recover the system without stopping the operation of the system.

(Fifth Embodiment)
Next, the encryption device according to the fifth embodiment of the present invention will be described with reference to the drawings. The encryption device of the present embodiment is different from the first embodiment in that the data scramble unit is duplicated and an abnormality in the data is also detected. In the following description, the same reference numerals may be given to the same configurations as those in the first embodiment, and detailed description may be omitted.

(Constitution)
FIG. 9 is a block diagram showing an example of the configuration of the encryption device 5 of the present embodiment. As shown in FIG. 9, in the encryption device 1 of the first embodiment, the encryption device 5 duplicates the data scramble unit 17 into the first data scramble unit 51 and the second data scramble unit 52, and compares the encryption blocks. It has a configuration in which a portion 53 is added.

In the first data scramble unit 51, a subkey is input from the subkey holding unit 13, and a plaintext block constituting the encryption target data is input. The first data scramble unit 51 uses the subkey to encrypt the input plaintext block. The first data scramble unit 51 outputs a ciphertext block (also referred to as a first ciphertext block), which is encrypted data, to the cipherblock comparison unit 53.

In the second data scramble unit 52, a subkey is input from the subkey holding unit 13, and a plaintext block constituting the encryption target data is input. The second data scramble unit 52 generates a ciphertext block by encrypting the input plaintext block using the subkey. The second data scramble unit 52 outputs the generated ciphertext block (also referred to as a second ciphertext block) to the ciphertext block comparison unit 53.

The first ciphertext block is input from the first data scramble unit 51, and the second ciphertext block is input from the second data scramble unit 52 to the cipher block comparison unit 53 (also referred to as a cipher block comparison means). The cipher block comparison unit 53 compares the input first ciphertext block and the second ciphertext block. In addition to the ciphertext block comparison, the cipher block comparison unit 53 may apply an authenticated cipher use mode.

When the first ciphertext block and the second ciphertext block are different from each other, the ciphertext comparison unit 53 determines that at least one of the first ciphertext block and the second ciphertext block is abnormal. That is, when the first ciphertext block and the second ciphertext block are different from each other, the ciphertext comparison unit 53 determines that the ciphertext block or the plaintext block corresponding to the ciphertext block has an abnormality. When the ciphertext comparison unit 53 determines that there is an abnormality in the ciphertext block or the plaintext block, it notifies the output determination unit 18 that there is an abnormality without outputting the ciphertext block.

On the other hand, when the first ciphertext block and the second ciphertext block are the same, the ciphertext comparison unit 53 determines that the first ciphertext block and the second ciphertext block are normal. That is, when the first ciphertext block and the second ciphertext block are the same, the ciphertext comparison unit 53 determines that the ciphertext block is normal. When the ciphertext comparison unit 53 determines that the ciphertext block is normal, it outputs either the first ciphertext block or the second ciphertext block to the output determination unit 18 as a ciphertext block.

When the output determination unit 18 is notified by the cipher block comparison unit 53 that there is an abnormality, the output determination unit 18 stops the output of the ciphertext block. For example, the output determination unit 18 may be configured to issue an instruction to display the notification result on a display device (not shown) or the like when the notification that there is an abnormality is received.

On the other hand, when the output determination unit 18 acquires the ciphertext block from the ciphertext comparison unit 53, the output determination unit 18 outputs the acquired ciphertext block.

Since other configurations are the same as those of the encryption device 1 of the first embodiment, detailed description thereof will be omitted.

The above is an explanation of an example of the configuration of the encryption device 5. Next, an example of the operation of the encryption device 5 will be described with reference to the drawings.

(motion)
FIG. 10 is a flowchart for explaining an example of the operation of the encryption device 5. That is, FIG. 10 is a flowchart showing the procedure of the encryption process executed by the encryption device 5. In the description according to the flowchart of FIG. 10 below, the encryption device 5 will be described as the main body of operation.

In FIG. 10, first, when the common key is input, the encryption device 5 stores the common key (also referred to as the first common key) in the first common key holding unit 11 (step S501).

Next, the encryption device 5 generates a subkey from the first common key stored in the first common key holding unit 11 by performing a key schedule by a block encryption algorithm of a common key method (step S502).

Next, the encryption device 5 stores the generated subkey in the subkey holding unit 13 (step S503).

The encryption device 5 double-encrypts the input plaintext block by the block cipher algorithm of the common key method by using the sub-key stored in the sub-key holding unit 13 (step S504). That is, the encryption device 5 generates two encryption blocks from the same plaintext block.

Next, the encryption device 5 compares two ciphertext blocks generated from the same plaintext block (step S505).

Further, the encryption device 5 executes a common key decryption process using the subkey stored in the subkey holding unit 13 in parallel with the processes of steps S504 and S505, and performs a common key decryption process (also known as a second common key). (Call) is decoded (step S506).

Next, the encryption device 5 stores the decrypted second common key in the second common key holding unit 15 (step S507).

Next, the encryption device 5 compares the first common key stored in the first common key holding unit 11 with the second common key stored in the second common key holding unit 15 (step S508).

Then, when the first common key and the second common key match (Yes in step S509), the encryption device 5 outputs a ciphertext block (step S510).

On the other hand, when the first common key and the second common key do not match (No in step S509), the encryption device 5 detects an abnormality in the subkey, performs error processing, and discards the ciphertext block. (Step S511).

The above is an explanation of an example of the operation of the encryption device 5 according to the flowchart of FIG.

As described above, the encryption device of the present embodiment double-encrypts the plaintext block to generate two encrypted blocks. Then, the encryption device of the present embodiment can detect an abnormality in data by comparing two encryption blocks.

(Sixth Embodiment)
Next, the decoding device according to the sixth embodiment of the present invention will be described with reference to the drawings. The decryption device of the present embodiment decrypts the ciphertext block output from the encryption device of the first embodiment. The decryption device of the present embodiment may be configured to decrypt the ciphertext block output from the encryption device of the second to fifth embodiments.

(Constitution)
FIG. 11 is a block diagram showing an example of the configuration of the decoding device 6 according to the present embodiment. As shown in FIG. 11, the decryption device 6 includes a first common key holding unit 61, a key schedule unit 62, a sub key holding unit 63, a common key decoding unit 64, a second common key holding unit 65, and a common key comparison unit 66. A data desk rumble unit 67 and an output determination unit 68 are provided.

The first common key holding unit 61 (also referred to as a first common key holding means) holds an input common key (hereinafter, also referred to as a first common key). For example, the first common key holding unit 61 is realized by a register or a memory.

The key schedule unit 62 (also referred to as a sub-key generation means) acquires the first common key held by the first common key holding unit 61. The key schedule unit 62 generates a subkey from the acquired first common key. For example, the key schedule unit 62 generates N subkeys used in all rounds from the first common key (N is a natural number). The key schedule unit 62 stores the generated subkey in the subkey holding unit 63.

The sub-key holding unit 63 (also referred to as a sub-key holding means) stores the sub-key generated by the key schedule unit 62. For example, the sub-key holding unit 63 is realized by a register or a memory.

The common key decryption unit 64 (also referred to as a common key decryption means) decodes a common key (hereinafter, also referred to as a second common key) from the subkey stored in the subkey holding unit 63. For example, the common key decryption unit 64 decodes the second common key from the N subkeys stored in the subkey holding unit 63 (N is a natural number). The common key decryption unit 64 causes the second common key holding unit 65 to hold the decrypted second common key.

The second common key holding unit 65 (also referred to as a second common key holding means) holds the second common key decrypted by the common key decoding unit 64. For example, the second common key holding unit 65 is realized by a register or a memory.

The common key comparison unit 66 (also referred to as a common key comparison means) compares the first common key held in the first common key holding unit 61 with the second common key held in the second common key holding unit 65. do. The common key comparison unit 66 outputs the comparison result of the first common key and the second common key to the output determination unit 68.

A subkey is input from the subkey holding unit 63 and an encryption block is input to the data descramble unit 67 (also referred to as a decryption means). The data scramble unit 67 decrypts the input encryption block by using the subkey. The data scramble unit 67 outputs the decoded plaintext block to the output determination unit 68.

A plaintext block is input from the data descramble unit 67 to the output determination unit 68 (also referred to as an output determination means), and a comparison result between the first common key and the second common key is input from the common key comparison unit 66. To. The output determination unit 68 determines whether or not to output the plaintext block based on the comparison result by the common key comparison unit 66. The output determination unit 68 determines that the plaintext block is output when the first common key and the second common key are the same. On the other hand, when the first common key and the second common key are different from each other, the output determination unit 68 detects an abnormality (also referred to as an error) such as a failure or tampering in the subkey, and discards the plaintext block without outputting it.

The above is the description of the configuration of the decoding device 6. As for the operation of the decryption device 6, since the encryption process (step S104) of the encryption device of the first embodiment may be replaced with the decryption process, detailed description thereof will be omitted.

As described above, according to the decoding device of the present embodiment, a large amount of data can be decoded safely and at high speed without affecting the processing performance.

(7th Embodiment)
Next, the line encryption system according to the seventh embodiment of the present invention will be described with reference to the drawings. FIG. 12 is a block diagram showing an example of the configuration of the line encryption system 7 of the present embodiment. As shown in FIG. 12, the line encryption system 7 includes at least one encryption device 71 and at least one decryption device 72.

The encryption device 71 corresponds to any of the encryption devices 1 to 5 of the first to fifth embodiments. For example, the encryption device 71 and the decryption device 72 are connected by at least one of a wired line and a wireless line. The encryption device 71 transmits the encryption block generated by encrypting the input plaintext block to the decryption device 72.

The decoding device 72 corresponds to the decoding device 6 of the sixth embodiment. The decryption device 72 receives the encryption block from the encryption device 71. The decryption device 72 decrypts the plaintext block from the received encrypted block by using the common key.

As described above, according to the line encryption system of the present embodiment, it is possible to construct a communication system capable of transmitting and receiving a large amount of data safely and at high speed without affecting the processing performance.

(hardware)
Here, the hardware configuration for realizing the encryption device or the decryption device according to each embodiment of the present invention will be described by taking the computer 90 of FIG. 13 as an example. The computer 90 in FIG. 13 is a configuration example for realizing the encryption device or the decryption device of each embodiment, and does not limit the scope of the present invention.

As shown in FIG. 13, the computer 90 includes a processor 91, a main storage device 92, an auxiliary storage device 93, an input / output interface 95, and a communication interface 96. In FIG. 13, the interface is abbreviated as I / F (Interface). The processor 91, the main storage device 92, the auxiliary storage device 93, the input / output interface 95, and the communication interface 96 are connected to each other via a bus 99 so as to be capable of data communication. Further, the processor 91, the main storage device 92, the auxiliary storage device 93, and the input / output interface 95 are connected to a network such as the Internet or an intranet via the communication interface 96.

The processor 91 expands the program stored in the auxiliary storage device 93 or the like to the main storage device 92, and executes the expanded program. In the present embodiment, the software program installed in the computer 90 may be used. The processor 91 executes the process by the encryption device or the decryption device according to the present embodiment.

The main storage device 92 has an area in which the program is developed. The main storage device 92 may be a volatile memory such as a DRAM (Dynamic Random Access Memory). Further, a non-volatile memory such as MRAM (Magnetoresistive Random Access Memory) may be configured / added as the main storage device 92.

The auxiliary storage device 93 stores various data. For example, the auxiliary storage device 93 is composed of a local disk such as a hard disk or a flash memory. It is also possible to store various data in the main storage device 92 and omit the auxiliary storage device 93.

The input / output interface 95 is an interface for connecting the computer 90 and peripheral devices. The communication interface 96 is an interface for connecting to an external system or device through a network such as the Internet or an intranet based on a standard or a specification. The input / output interface 95 and the communication interface 96 may be shared as an interface for connecting to an external device.

The computer 90 may be configured to connect an input device such as a keyboard, a mouse, or a touch panel, if necessary. These input devices are used to input information and settings. When the touch panel is used as an input device, the display screen of the display device may also serve as the interface of the input device. Data communication between the processor 91 and the input device may be mediated by the input / output interface 95.

Further, the computer 90 may be equipped with a display device for displaying information. When a display device is provided, it is preferable that the computer 90 is provided with a display control device (not shown) for controlling the display of the display device. The display device may be connected to the computer 90 via the input / output interface 95.

Further, the computer 90 may be equipped with a disk drive, if necessary. The disk drive is connected to bus 99. The disk drive mediates between the processor 91 and a recording medium (program recording medium) (not shown), reading a data program from the recording medium, writing the processing result of the computer 90 to the recording medium, and the like. The recording medium can be realized by, for example, an optical recording medium such as a CD (Compact Disc) or a DVD (Digital Versatile Disc). Further, the recording medium may be realized by a semiconductor recording medium such as a USB (Universal Serial Bus) memory or an SD (Secure Digital) card, a magnetic recording medium such as a flexible disk, or another recording medium.

The above is an example of a hardware configuration for enabling an encryption device or a decryption device according to each embodiment of the present invention. The hardware configuration of FIG. 13 is an example of a hardware configuration for executing arithmetic processing of the encryption device or the decryption device according to each embodiment, and does not limit the scope of the present invention. Further, a program for causing a computer to execute a process related to an encryption device or a decryption device according to each embodiment is also included in the scope of the present invention. Further, a program recording medium on which a program according to each embodiment is recorded is also included in the scope of the present invention.

The components of the encryption device or decryption device of each embodiment can be arbitrarily combined. Further, the components of the encryption device or the decryption device of each embodiment may be realized by software or may be realized by a circuit.

Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above embodiments. Various modifications that can be understood by those skilled in the art can be made to the structure and details of the present invention within the scope of the present invention.
[Additional Notes]
Some or all of the above embodiments may also be described, but not limited to:
(Appendix 1)
The first common key holding means for holding the first common key,
A subkey generation means for generating at least one subkey from the first common key held by the first common key holding means by a key schedule, and a subkey generating means.
A subkey holding means for holding the subkey generated by the subkey generating means, and a subkey holding means.
A common key decryption means for acquiring the subkey held by the subkey holding means and decrypting the second common key,
A second common key holding means for holding the second common key decrypted by the common key decrypting means, and a second common key holding means.
A common key comparison means for comparing the first common key held by the first common key holding means with the second common key held by the second common key holding means.
An encryption means that encrypts a plaintext block using the subkey held by the subkey holding means to generate a ciphertext block, and
The comparison result between the first common key and the second common key by the common key comparison means and the ciphertext block generated by the encryption means are input, and based on the comparison result by the common key comparison means. An encryption device including an output determination means for determining whether or not to output the ciphertext block.
(Appendix 2)
The output determination means is
When the first common key and the second common key are the same, the ciphertext block is output.
The encryption device according to Appendix 1, which discards the ciphertext block when the first common key and the second common key are different.
(Appendix 3)
A subkey determining means for comparing the input common key with the first common key held by the first common key holding means and determining whether or not to generate the subkey is provided.
The sub-key determination means is
When the input common key and the first common key are different, the input common key is held by the first common key holding means as the first common key, and the first common key holding means is newly used. Instructed the sub-key generation means to generate the sub-key from the first common key held in the key.
The encryption device according to Appendix 1 or 2, wherein when the input common key and the first common key are equal, the subkey generation means is not instructed to generate the subkey.
(Appendix 4)
Pseudo-random number generation means that generates pseudo-random numbers according to encryption instructions,
A common key generation means for generating a common key using the pseudo-random number generated by the pseudo-random number generation means and holding the generated common key as the first common key in the first common key holding means is provided. The encryption device according to Appendix 1 or 2.
(Appendix 5)
A retry determination means for determining whether or not an abnormality is suspected in the subkey is provided based on the comparison result between the first common key and the second common key by the common key comparison means.
The retry determination means is
If it is suspected that the subkey is abnormal, the subkey generation means is instructed to regenerate the subkey.
The encryption device according to any one of Supplementary note 1 to 4, wherein when it is not suspected that the subkey has an abnormality, the comparison result by the common key comparison means is output to the output determination means.
(Appendix 6)
The encryption means is duplicated,
A cipherblock comparison means is provided in which at least two ciphertext blocks generated from the same plaintext block by the duplicated cryptographic means are input and the input at least two ciphertext blocks are compared.
The cipher block comparison means is
If at least two input ciphertext blocks are different, it is determined that there is an abnormality, and the ciphertext block is not output to the output determination means.
The encryption device according to any one of Supplementary note 1 to 5, wherein if at least two input ciphertext blocks are equal, it is determined that the ciphertext block is normal, and the ciphertext block is output to the output determination means.
(Appendix 7)
The first common key holding means for holding the first common key,
A subkey generation means for generating at least one subkey from the first common key held by the first common key holding means by a key schedule, and a subkey generating means.
A subkey holding means for holding the subkey generated by the subkey generating means, and a subkey holding means.
A common key decryption means for acquiring the subkey held by the subkey holding means and decrypting the second common key,
A second common key holding means for holding the second common key decrypted by the common key decrypting means, and a second common key holding means.
A common key comparison means for comparing the first common key held by the first common key holding means with the second common key held by the second common key holding means.
A decryption means for decrypting a plaintext block from a ciphertext block using the subkey held in the subkey holding means,
The comparison result between the first common key and the second common key by the common key comparison means and the plaintext block decoded by the decoding means are input, and the plaintext is based on the comparison result by the common key comparison means. A decoding device including an output determination means for determining whether or not to output a block.
(Appendix 8)
At least one subkey is generated from the first common key in a key schedule, the plain text block is encrypted using the generated subkey to generate a ciphertext block, and the generated subkey is used for the first. 2. An encryption device that decrypts the common key and determines whether or not to output the ciphertext block based on the comparison result between the first common key and the second common key.
At least one subkey is generated from the first common key by a key schedule, the plaintext block is decrypted from the ciphertext block using the generated subkey, and the generated subkey is used to decode the plaintext block. It is provided with a decoding device that decodes the second common key and determines whether or not to output the plaintext block based on the comparison result between the first common key and the second common key.
The encryption device is
The ciphertext block obtained by encrypting the plaintext block is transmitted to the decryption device, and the ciphertext block is transmitted to the decryption device.
The decoding device is
A line encryption system that decrypts the plaintext block from the ciphertext block received from the encryption device.
(Appendix 9)
Hold the first common key in the first common key holding means,
At least one subkey is generated from the first common key held by the first common key holding means by a key schedule.
The generated sub-key is held in the sub-key holding means, and the generated sub-key is held in the sub-key holding means.
The second common key is decrypted using the subkey held by the subkey holding means, and the second common key is decrypted.
The decrypted second common key is held in the second common key holding means, and the decrypted second common key is held in the second common key holding means.
The first common key held by the first common key holding means and the second common key held by the second common key holding means are compared.
The plaintext block is encrypted using the subkey held by the subkey holding means to generate a ciphertext block.
An encryption method for determining whether or not to output the ciphertext block based on a comparison result between the first common key and the second common key.
(Appendix 10)
The process of holding the first common key in the first common key holding means,
A process of generating at least one subkey from the first common key held by the first common key holding means by a key schedule, and
The process of holding the generated subkey in the subkey holding means,
The process of decrypting the second common key using the subkey held by the subkey holding means, and
The process of holding the decrypted second common key in the second common key holding means,
A process of comparing the first common key held by the first common key holding means with the second common key held by the second common key holding means.
A process of encrypting a plaintext block using the subkey held by the subkey holding means to generate a ciphertext block, and
A program that causes a computer to execute a process of determining whether or not to output the ciphertext block based on a comparison result between the first common key and the second common key.
(Appendix 11)
Hold the first common key in the first common key holding means,
At least one subkey is generated from the first common key held by the first common key holding means by a key schedule.
The generated sub-key is held in the sub-key holding means, and the generated sub-key is held in the sub-key holding means.
The second common key is decrypted using the subkey held by the subkey holding means, and the second common key is decrypted.
The decrypted second common key is held in the second common key holding means, and the decrypted second common key is held in the second common key holding means.
The first common key held by the first common key holding means and the second common key held by the second common key holding means are compared.
The plaintext data is decrypted from the ciphertext block using the subkey held in the subkey holding means, and the plaintext data is decrypted.
An encryption method for determining whether or not to output the plaintext data based on a comparison result between the first common key and the second common key.
(Appendix 12)
The process of holding the first common key in the first common key holding means,
A process of generating at least one subkey from the first common key held by the first common key holding means by a key schedule, and
The process of holding the generated subkey in the subkey holding means,
The process of decrypting the second common key using the subkey held by the subkey holding means, and
The process of holding the decrypted second common key and
A process of comparing the first common key held by the first common key holding means with the second common key held by the second common key holding means.
A process of decrypting plaintext data from a ciphertext block using the subkey held in the subkey holding means, and
A program that causes a computer to execute a process of determining whether or not to output the plaintext data based on a comparison result between the first common key and the second common key.

1, 2, 3, 4, 5 Encryption device 6 Decryption device 7 Line encryption system 11 1st common key holding unit 12 Key schedule unit 13 Sub key holding unit 14 Common key decryption unit 15 2nd common key holding unit 16 Common key Comparison part 17 Data scramble part 18 Output judgment part 21 Subkey generation judgment part 31 Pseudo-random key generation part 32 Common key generation part 41 Retry judgment part 51 First data scramble part 52 Second data scramble part 53 Cryptographic block comparison part 67 Data Scramble part 71 Encryption device 72 Decryption device

Claims (7)

The first common key holding means for holding the first common key,
A subkey generation means for generating at least one subkey from the first common key held by the first common key holding means by a key schedule, and a subkey generating means.
A subkey holding means for holding the subkey generated by the subkey generating means, and a subkey holding means.
A common key decryption means for acquiring the subkey held by the subkey holding means and decrypting the second common key,
A second common key holding means for holding the second common key decrypted by the common key decrypting means, and a second common key holding means.
A common key comparison means for comparing the first common key held by the first common key holding means with the second common key held by the second common key holding means.
An encryption means for generating a ciphertext block by encrypting a plaintext block using the subkey held by the subkey holding means in parallel with decryption of the second common key .
A retry determination means for determining whether or not an abnormality is suspected in the subkey based on the comparison result between the first common key and the second common key by the common key comparison means.
The comparison result between the first common key and the second common key by the common key comparison means and the ciphertext block generated by the encryption means are input, and based on the comparison result by the common key comparison means. It is provided with an output determination means for determining whether or not to output the ciphertext block.
If it is suspected that the subkey is abnormal, the retry determination means instructs the subkey generation means to regenerate the subkey.
If it is not suspected that the subkey has an abnormality, the output determination means is an encryption device that outputs the ciphertext block . The output determination means is
When the first common key and the second common key are the same, the ciphertext block is output.
The encryption device according to claim 1, wherein when the first common key and the second common key are different, the ciphertext block is destroyed. A subkey determining means for comparing the input common key with the first common key held by the first common key holding means and determining whether or not to generate the subkey is provided.
The sub-key determination means is
When the input common key and the first common key are different, the input common key is held by the first common key holding means as the first common key, and the first common key holding means is newly used. Instructed the sub-key generation means to generate the sub-key from the first common key held in the key.
The encryption device according to claim 1 or 2, wherein when the input common key and the first common key are equal, the subkey generation means is not instructed to generate the subkey. Pseudo-random number generation means that generates pseudo-random numbers according to encryption instructions,
A common key generation means for generating a common key using the pseudo-random number generated by the pseudo-random number generation means and holding the generated common key as the first common key in the first common key holding means is provided. The encryption device according to claim 1 or 2. The encryption means is duplicated,
A cipherblock comparison means is provided in which at least two ciphertext blocks generated from the same plaintext block by the duplicated cryptographic means are input and the input at least two ciphertext blocks are compared.
The cipher block comparison means is
If at least two input ciphertext blocks are different, it is determined that there is an abnormality, and the ciphertext block is not output to the output determination means.
The encryption device according to any one of claims 1 to 4 , wherein when at least two input ciphertext blocks are equal, it is determined that the ciphertext block is normal and the ciphertext block is output to the output determination means. Hold the first common key in the first common key holding means,
At least one subkey is generated from the first common key held by the first common key holding means by a key schedule.
The generated sub-key is held in the sub-key holding means, and the generated sub-key is held in the sub-key holding means.
The second common key is decrypted using the subkey held by the subkey holding means, and the second common key is decrypted.
The decrypted second common key is held in the second common key holding means, and the decrypted second common key is held in the second common key holding means.
The first common key held by the first common key holding means and the second common key held by the second common key holding means are compared.
In parallel with the decryption of the second common key, the plaintext block is encrypted using the subkey held by the subkey holding means to generate a ciphertext block.
Based on the comparison result between the first common key and the second common key, it is determined whether or not the subkey is suspected to be abnormal.
If it is suspected that the subkey is abnormal, the subkey is instructed to be regenerated, and the subkey is instructed to be regenerated.
An encryption method that outputs the ciphertext block when it is not suspected that the subkey has an abnormality . The process of holding the first common key in the first common key holding means,
A process of generating at least one subkey from the first common key held by the first common key holding means by a key schedule, and
The process of holding the generated subkey in the subkey holding means,
The process of decrypting the second common key using the subkey held by the subkey holding means, and
The process of holding the decrypted second common key in the second common key holding means,
A process of comparing the first common key held by the first common key holding means with the second common key held by the second common key holding means.
In parallel with the process of decrypting the second common key, a process of encrypting a plaintext block using the subkey held by the subkey holding means to generate a ciphertext block, and a process of generating a ciphertext block.
Based on the comparison result between the first common key and the second common key , a process of determining whether or not the subkey is suspected to be abnormal, and a process of determining whether or not the subkey is suspected to be abnormal.
If it is suspected that there is an abnormality in the subkey, it is instructed to regenerate the subkey, and if it is not suspected that there is an abnormality in the subkey, the process of outputting the ciphertext block is performed by the computer. Program to be executed by.

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