Anonymous authentication system and anonymous authentication method

An anonymous authentication system comprising a group management device for managing a group of users, an authentication-subjected user device for requesting verification as to whether or not a user who is to be authenticated belongs to the group, in accordance with the user's operation, a verification device for receiving the verification request and for verifying that the user who is to be authenticated and who has requested the authentication belongs to the group, a authentication assistant device for assisting in the authenticating operation, a verification assistant device for assisting in the verifying operation, and an authentication-subjected user identification device for identifying the user who is to be authenticated, wherein:

• said authentication-subjected user device generates an authentication assist request from open information of the group to which the user to be authenticated belongs, open information and secret information which are unique to the user, and an information nonce which is generated at each authentication,
• said authentication assistant device responds to the authentication assist request, extracts information regarding the open information and secret information which are unique to the user from secret information which corresponds to the open information of the group and the authentication assist request, verifies, from a list of user's open information which is managed by the group, that the user who belongs to the group has generated said authentication assist request, and generates authentication assist data from the result of the verification, the open information and secret information of the group,
• said authentication-subjected user device generates unlinkable authentication data including the authentication assist data received from said verification assistant device which has responded to the authentication assist request,
• said verification device verifies, from said unlinkable authentication data and the open information of the group, that the authentication assist data included in said unlinkable authentication data is data which is generated using the open information and secret information of the group to obtain the result of verification as to whether or not the user who is to be authenticated belongs to the group, and
• said authentication-subjected user identification device identifies the user who is to be authenticated and who corresponds to said unlinkable authentication data from said unlinkable authentication data, the secret key of the group and the list of user's open information which is managed by the group,
• wherein said verification device carries out an anonymous authentication of the user who is to be authenticated based on an identification of the user by the verification assistant device.

An anonymous authentication system comprising a group management device for managing a group of users, an authentication-subjected user device for requesting verification as to whether or not a user who is to be authenticated belongs to the group, in accordance with the user's operation, a verification device for receiving the verification request and for verifying that the user who is to be authenticated and who has requested the verification belongs to the group, an authentication assistant device for assisting in the authenticating operation, a verification assistant device for assisting in the verifying operation, and an authentication-subjected user identification device for identifying the user who is to be authenticated, wherein:

• said authentication-subjected user device generates an authentication assist request from open information of the group, open information and secret information which are unique to the user, and an information nonce which is generated at each authentication,
• said authentication assistant device responds to the authentication assist request, extracts information regarding the open information and secret information which are unique to the user from secret information which corresponds to the open information of the group and the authentication assist request, verifies, from a list of user's open information which is managed by the group, that the user who belongs to the group has generated said authentication assist request, and generates authentication assist data from the result of the verification and the open information of the group,
• said verification assistant device extracts information regarding the open information and public information which are unique to the user from unlinkable authentication data using secret information which corresponds to the open information of said group, verifies, from the list of user's open information which is managed by the group, that the user who belongs to the group has generated said unlinkable authentication data, and generates verification assist data from the result of the verification,
• said verification device receives said unlinkable authentication data from said authentication-subjected user device, transmits verification assist request including said unlinkable authentication data to said verification assistant device, receives the verification assist data from said verification assistant device which has responded to the verification assist request, and generates from the verification assist data result of verification as to whether or not the user who is to be authenticated belongs to the group,
• said authentication-subjected user identification device identifies the user who is to be authenticated and who corresponds to said unlinkable authentication data from said unlinkable authentication data, the secret key of the group and the list of user's open information which is managed by the group,
• wherein said verification device carries out an anonymous authentication of the user who is to be authenticated based on an identification of the user by the verification assistant device.