CRYPTOGRAPHIC SYSTEM ALLOWING ENCRYPTED COMMUNICATION BETWEEN USERS WITH A SECURE MUTUAL CIPHER KEY DETERMINED WITHOUT USER INTERACTION

摘要

A secret key generator for a trusted authority means in a cryptographic system comprising means for receiving a publicly-known user identity IDA for a user A; and further comprising secret key generator means for transforming the publicly-known user identity ID A into secret key s A for the user A with the inverse of the exponentiation function a s A ~ (ID A)2 (mod m), that is solved for s A, where a is a publicly-known base parameter, where m is a publicly-known modulus parameter and m = p1 * P2 ~~~ * Pr, and where p1, P2, ..., pr are secret system prime numbers. The inverse of the exponentiation function is infeasible to compute in order to calculate the secret key s A without knowing the prime numbers p1, p2, ..., Pr. The secret key s A enables user A to communicate securely to a user B having publicly-known user identity ID B with a mutual secure cipher key K AB, defined by the equation: K AB ~ (ID B) 2s A (mod m). The mutual secure cipher key K AB is determined without previous interaction with the user B.