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 ID_A 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 functionthat 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, ···, P_r, and where pi, p₂, ..., P_r 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,···, P_r. 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:;The mutual secure cipher key K_AB is determined without previous interaction with the user B.