CRYPTOSYSTEM, CRYPTOGRAPHIC COMMUNICATION METHOD, ENCRYPTION DEVICE, KEY-GENERATING DEVICE, DECRYPTION DEVICE, CONTENT SERVER DEVICE, PROGRAM, AND RECORDING MEDIUM

摘要

A cryptographic communication technology that is based on functional encryption and that can operate flexibly is provided. A conversion rule information pair is determined in advance, which has attribute conversion rule information prescribing a conversion rule for converting attribute designation information to attribute information used in a functional encryption algorithm and logical expression conversion rule information prescribing a conversion rule for converting logical expression designation information to logic information used in the functional encryption algorithm. One kind of conversion rule information included in the conversion rule information pair is used to obtain first attribute information or first logic information from input information. The first attribute information or the first logic information is used for encryption. Encryption information is decrypted with a decryption key generated by using second attribute information or second logic information obtained from user information by using the other kind of conversion rule information.