METHOD FOR ENABLING USER TO CHECK LEGALITY OF ELECTRONIC COMMERCE/INFORMATION SERVICE PROVIDER

摘要

PPROBLEM TO BE SOLVED: To provide a high speed processing non-repudiation signing system. PSOLUTION: When imparting public keys (D, P, k, t) and secret keys (Dl, q), at a verifier side, when a norm N(S) of a signature S is smaller than (k) bits, a message ideal M of a message (m) is calculated, a random number (r) smaller than (t) bits is generated to calculate H=(M/S)SPr/SP, and a random number ideal B whose norm is smaller than (k-1) bits is generated to calculate C=BH, so that a challenge C is generated. At a signer side, the secret keys (Dl, q) are used to map the challenge C to a class group Cl(Dl), the mapped challenge C is pulled back to a class group Cl(D), and the result of mapping and pulling-back is squared to generate a response W. At the verifier side, it is checked whether W=BSP2/SPis established or not and when it is established, the signature S is judged legal. PCOPYRIGHT: (C)2004,JPO&NCIPI