ENCIPHERING METHOD, AND DECODING METHOD AND DEVICE

摘要

PROBLEM TO BE SOLVED: To provide an enciphering method and decoding method and device having higher secrecy by setting a cipher use mode. SOLUTION: A key data storing part 105 stores a cryptographic key including the cipher use mode. A cipher use mode selection signal generating part 104 reads the cryptographic key from the part 105 and outputs a selection signal selecting the cipher use mode. A cipher use mode controlling part 102 sets the cipher use mode of a cipher/decode algorithm part 101 by the selection signal. An encipher/decode processing part 103 converts plaintext or cryptography from a data inputting and outputting part 106 into the data of cryptography or plaintext according to the above setting and outputs the data. Secrecy can be improved because a cipher operation mode is set in addition to the cryptographic key of encipher/decoding by including the information of the cipher use mode (chain technique) in the cryptographic key.