Patent ID: 8995660
Filing Date: 2015-03-31
Classification: H04L

Abstract:
1. A cryptographic system that uses functional encryption, comprising at least: one or a plurality of encryption apparatuses; one or a plurality of key generation apparatuses; and one or a plurality of decryption apparatuses; wherein a private key and a public key corresponding to the private key are determined in advance for each of the one or the plurality of key generation apparatuses; one or a plurality of conversion rule information pairs are determined in advance, each pair of which has attribute conversion rule information prescribing a conversion rule for converting attribute designation information that designates an attribute 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 that designates a logical expression to logic information used in the functional encryption algorithm; policy information that identifies one of the attribute conversion rule information and the logical expression conversion rule information is determined in advance; each of the one or the plurality of encryption apparatuses comprises circuitry configured to: use one kind of conversion rule information of the attribute conversion rule information and the logical expression conversion rule information included in one conversion rule information pair selected from the one or the plurality of conversion rule information pairs, the one kind of conversion rule information being selected together with the policy information according to whether input information input to the encryption apparatus is either attribute designation information or logical expression designation information, to obtain first attribute information or first logic information from the input information; and use the first attribute information or the first logic information, together with the public key of the key generation apparatus, to obtain a common key, and encryption information corresponding to the common key or corresponding to information used to generate the common key, according to the functional encryption algorithm; each of the one or the plurality of key generation apparatuses comprises circuitry configured to: use the conversion rule information paired with the conversion rule information identified by the policy information to obtain second attribute information or second logic information from attribute designation information or logical expression designation information corresponding to a user of the decryption apparatus; and use the second attribute information or the second logic information, together with the private key of the key generation apparatus, to generate a decryption key used to decrypt the encryption information; and each of the one or the plurality of decryption apparatuses comprises circuitry configured to use the decryption key to apply a decryption process to the encryption information according to the functional encryption algorithm.