A signature unit, in which a user device generates/transmits digital signature data to an authentication device, includes: a first function, which receives as input a plurality of subsets in which a plurality of characteristics of the users are classified; a second function, which generates a first encrypted text acquired by encrypting a user device public key with an identification device public key; a third function, which generates a second encrypted text, acquired by encrypting characteristic values belonging to a specific subset among the subsets with a characteristic value disclosure device public key; and a fourth function, which employs portions of a group public key and a member certificate to generates a signature of knowledge that denotes that data, of multiplication of a portion of the user device public key and all of the numerical values of a characteristic value certificate corresponding to each of the characteristics, satisfies the specific conditions.
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