CRYPTOGRAM SYSTEM, CRYPTOGRAM COMMUNICATION METHOD, ENCRYPTING DEVICE, KEY GENERATING DEVICE, DECRYPTING DEVICE, CONTENT SERVER DEVICE, PROGRAMS, AND STORAGE MEDIUM

摘要

Provided is a cryptogram communication method that relies on predicate cryptogram, which can be implemented flexibly. Prescribed in advance is a conversion-rules information pair, which is a pair of: attribute conversion-rules information, which prescribes conversion rules for converting attribute-specifying information into attribute information to be used in predicate-cryptogram algorithms; and predicate conversion-rules information, which prescribes conversion rules for converting predicate-specifying information into predicate information to be used in the predicate-cryptogram algorithms. First attribute information or first predicate information is obtained from the inputted information, using one of the conversion-rules information included in this conversion-rules information pair. This information will be used for encryption processing. In decryption processing, decryption processing of cryptogram information will be conducted using a decryption key created with second attribute information or second predicate information, obtained from user information using the other conversion-rules information.