Patent ID: 8499158

Claim:
An anonymous service method of providing local linkability, the method comprising: a service user joining operation of acquiring, by a service terminal, a group signature secret key of a service user in cooperation with an anonymous authentication server; a service providing server joining operation of acquiring, by a service providing server, a pair of a partial linkage public key and a secret key of a service provider in cooperation with an anonymous ID checking server; a group signature generating operation of receiving, by the service terminal, the public key from the service providing server, and generating a group signature of the service user based on the public key and the group signature secret key; a group signature verifying operation of verifying, by the service providing server, whether or not the group signature is valid; a signer checking operation of calculating, by the anonymous ID checking server, an anonymous ID from the group signature, and checking the service user having the anonymous ID in cooperation with the anonymous authentication server; a local linking operation of checking, by the service providing server, whether or not the group signature is proper through the public key and acquiring a virtual index of the service user from the group signature through the secret key in order to secure a local linkability of the service user; and a group generating operation of generating, by the anonymous authentication server, a group public key and a group member key generation secret key with a group public parameter, and releasing the group public parameter and the group public key, before the service user joining operation.