Patent ID: 7779262
Filing Date: 2010-08-17
Classification: H04L

Abstract:
1. A security method using an electronic signature, comprising: (a) generating a public key and an secret key comprising two pieces of information which are independent of each other, by a certificate authority, in response to a request from a user terminal device, wherein the public key comprises a first public key value and a second public key value, and the secret key comprises a first secret key piece computed based on the first public key value and a second secret key piece computed based on the second public key value, and the first secret key piece is divided into a user's secret key and a mediator's secret key; (b) issuing the two pieces of information the user's secret key to the user terminal device and the mediator's secret key and the second secret key piece to a semi-trusted party, respectively; (c) transmitting a first signature piece generated from-based on the computation key and the second key piece the two issued pieces of information of the secret key, to the user terminal device from the semi-trusted party when a certificate of the user terminal device is still valid; (d) utilizing the first signature piece and a second signature piece, by the user terminal device, to generate a signature value, the second signature piece being generated by a combination of the first signature piece an issued secret key piece and a predetermined value; and (e) confirming whether the signature value is valid.