An encryption apparatus (10 - Figure 5) for use for a cryptographic system (1- Figure 1) that uses functional encryption and includes, at least, one or a plurality of encryption apparatuses (10 - Figure 5), one or a plurality of key generation apparatuses (20 - Figure 1), and one or a plurality of decryption apparatuses (30 - Figure 1), 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 (20 - Figure 1); 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; and policy information that identifies one of the attribute conversion rule information and the logical expression conversion rule information is determined in advance; the encryption apparatus (10 - Figure 5) comprising: a first propositional logic information acquisition unit (12 - Figure 5) adapted 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 (10 - Figure 5) is either attribute designation information or logical expression designation information, to obtain attribute information that is hereafter called first attribute information or logic information that is hereafter called first logic information from the input information; and an encryption unit (13 - Figure 5) adapted to use the first attribute information or the first logic information, together with the public key of the key generation apparatus (20 - Figure 1), 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. a first propositional logic information acquisition unit (12 - Figure 5) adapted 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 (10 - Figure 5) is either attribute designation information or logical expression designation information, to obtain attribute information that is hereafter called first attribute information or logic information that is hereafter called first logic information from the input information; and an encryption unit (13 - Figure 5) adapted to use the first attribute information or the first logic information, together with the public key of the key generation apparatus (20 - Figure 1), 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.