To provide a personal authentication device of structure capable of authenticating a user using an existing portable authentication medium or the like issued by a third institution.

This personal authentication device stores the combination of cipher data acquired from the portable authentication medium C, and personal data acquired for each user when registering the user, and retrieves the personal data combined with the cipher data acquired from the portable authentication medium C when authenticating the user. The user is authenticated thereby without decoding the cipher data of the portable authentication medium C by confirming whether the user carries the same portable authentication medium C in the registration and the authentication or not.

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