Data processing device

Abstract

A certification deviceencrypts a feature vector for registration by using a random number and a public key which is set to correspond to a secret key in a decryption device. The encrypted feature vector for registration is registered in an authentication device. In authentication, the certification device encrypts a feature vector for authentication by using the public key and a random number. With the two encrypted feature vectors being kept encrypted, the authentication device generates encrypted similarity degree information from which the decryption device can derive the similarity degree between the two feature vectors by a decryption process using the secret key. The decryption devicedecrypts the encrypted similarity degree information to derive the similarity degree of the plaintext. The authentication device, if the similarity degree is equal to or larger than a threshold, determines that the user is the correct user. The similarity degree can be derived without using the feature vector of the plaintext. Thus, secure identity authentication with a lower possibility of plaintext theft can be realized.