Patent ID: 8041944
Filing Date: 2011-10-18
Classification: H04L

Abstract:
1. A group signature system including an issuing device, a disclosing device, a revocation manager, a user device and a verifying device, being connected to each other via a network, said issuing device including an issuing device storage in which elements of a first cyclic group are stored, and an issuing device controller which, when issuing device public key ipk of a set that includes order N of said first cyclic group and elements a_ said user device including a user device storage in which a set of primes are stored, and a user device controller which, when receiving said disclosed issuing device public key ipk, determines such primes e and e′ that e′ is a prime that is obtained by subtracting a fixed number smaller than said prime e from said prime e, generates user device secret key msk of a set including such numbers x and r that a product between said a_ said verifying device including a verifying device storage for storing said message and said signature statement, and a verifying device controller which, when receiving said message and said signature statement, performs verification by using said message and a signature statement candidate to verify a validity of said signature statement candidate and outputs whether said signature statement candidate is valid or not, and said disclosing device including a disclosing device storage for storing said message and said signature statement, and a disclosing device controller which, when receiving said message and said signature statement to confirm that said signature statement is valid, calculates h by decoding based on said message, said signature statement, generated disclosing device public key opk and disclosing device secret key osk and outputs said h.