Encryption method , decoding method , the encryption apparatus , decryption apparatus and encryption / decryption system .

摘要

PROBLEM TO BE SOLVED: To prevent a first ciphertext block from becoming a step to decryption when encrypting plaintext in an encryption block chain mode, and to make a length of ciphertext equal to that of plaintext.;SOLUTION: When encrypting plaintext (M1...Mn) in an encryption block chain mode, an encryption apparatus 10 encrypts plaintext (P, M1...Mn) in which a preblock (P) generated by a preblock generator 12 is added to the head, and defines a result of removing ciphertext block (Cp) corresponding to the preblock (P) from ciphertext (Cp, C1...Cn) obtained by encrypting the plaintext (P, M1...Mn) as ciphertext (C1...Cn) of the plaintext (M1...Mn).;COPYRIGHT: (C)2012,JPO&INPIT