Encryption processing circuit and decryption processing circuit, methods thereof, and programs thereof

An encryption processing circuit that encrypts plain text in a plurality of steps by using a cryptographic key, the circuit comprising:

• N (N is an integer equal to 2 or greater) sets, each of which including an encryption block and a register, wherein:
• the encryption block of an i-th (i=1 to N−1) set performs encryption in a certain step on plain text stored in the register of the i-th set or intermediate data stored in the register of the i-th set obtained from the plain text and intermediate data obtained by the encryption is stored in the register of an (i+1)-th set, and
• the encryption block of an N-th set performs the encryption in a certain step on plain text stored in the register of the N-th set or intermediate data stored in the register of the N-th set obtained from the plain text and intermediate data obtained by the encryption is stored in the register of a first set.

A decryption processing circuit that decrypts cipher text in a plurality of steps by using a cryptographic key, the circuit comprising:

• N (N is an integer equal to 2 or greater) sets, each of which including a decryption block and a register, wherein:
• the decryption block of an i-th (i=1 to N−1) set performs decryption in a certain step on cipher text stored in the register of the i-th set or intermediate data stored in the register of the i-th set obtained from the cipher text and intermediate data obtained by the decryption is stored in the register of an (i+1)-th set, and
• the decryption block of an N-th set performs the decryption in a certain step on cipher text stored in the register of the N-th set or intermediate data stored in the register of the N-th set obtained from the cipher text and intermediate data obtained by the decryption is stored in the register of a first set.

An encryption processing method of encrypting plain text in a plurality of steps by using a cryptographic key, wherein:

• N (N is an integer equal to 2 or greater) sets, each of which including an encryption block and a register, are used,
• the encryption block of an i-th (i=1 to N−1) set performs encryption in a certain step on plain text stored in the register of the i-th set or intermediate data stored in the register of the i-th set obtained from the plain text and intermediate data obtained by the encryption is stored in the register of an (i+1)-th set, and
• the encryption block of an N-th set performs the encryption in a certain step on plain text stored in the register of the N-th set or intermediate data stored in the register of the N-th set obtained from the plain text and intermediate data obtained by the encryption is stored in the register of a first set.

A decryption processing method of decrypting cipher text in a plurality of steps by using a cryptographic key, wherein:

• N (N is an integer equal to 2 or greater) sets, each of which including a decryption block and a register, are used,
• the decryption block of an i-th (i=1 to N−1) set performs decryption in a certain step on cipher text stored in the register of the i-th set or intermediate data stored in the register of the i-th set obtained from the cipher text and intermediate data obtained by the decryption is stored in the register of an (i+1)-th set, and
• the decryption block of an N-th set performs the decryption in a certain step on cipher text stored in the register of the N-th set or intermediate data stored in the register of the N-th set obtained from the cipher text and intermediate data obtained by the decryption is stored in the register of a first set.

A non-transitory computer readable medium storing an encryption processing program causing a computer to function as an encryption processing circuit that encrypts plain text in a plurality of steps by using a cryptographic key, wherein:

• the encryption processing circuit comprises N (N is an integer equal to 2 or greater) sets, each of which including an encryption block and a register,
• code is contained so that the encryption block of an i-th (i=1 to N−1) set performs encryption in a certain step on plain text stored in the register of the i-th set or intermediate data stored in the register of the i-th set obtained from the plain text and intermediate data obtained by the encryption is stored in the register of an (i+1)-th set in the encryption processing circuit and
• code is contained so that the encryption block of an N-th set performs the encryption in a certain step on plain text stored in the register of the N-th set or intermediate data stored in the register of the N-th set obtained from the plain text and intermediate data obtained by the encryption is stored in the register of a first set in the encryption processing circuit.

A non-transitory computer readable medium storing a decryption processing program causing a computer to function as a decryption processing circuit that decrypts cipher text in a plurality of steps by using a cryptographic key, wherein:

• the decryption processing circuit comprises N (N is an integer equal to 2 or greater) sets, each of which including a decryption block and a register,
• code is contained so that the decryption block of an i-th (i=1 to N−1) set performs decryption in a certain step on cipher text stored in the register of the i-th set or intermediate data stored in the register of the i-th set obtained from the cipher text and intermediate data obtained by the decryption is stored in the register of an (i+1)-th set in the decryption processing circuit, and
• code is contained so that the decryption block of an N-th set performs the decryption in a certain step on cipher text stored in the register of the N-th set or intermediate data stored in the register of the N-th set obtained from the cipher text and intermediate data obtained by the decryption is stored in the register of a first set in the decryption processing circuit.