Patent ID: 7266692

Claim:
A computer-implemented authentication method for providing authentication, in each of a plurality of predefined periods of time, as to whether or not elements possess a pre-specified property, each element being operable to acquire the property and/or to lose the property, each element being associated with a distinct integer greater than 1, the method comprising, for each period j of said periods of time, and for a set P 1 j of said elements, obtaining first data A 1 (P 1 j ) evidencing that all the elements of the set P 1 j possess said property in the period j or all the elements of the set P 1 j do not possess said property in the period j, wherein the first data A 1 (P 1 j ) represents a P j -th root u 1/P j (mod n) of an integer u modulo a predefined composite integer n, where P j is the product of the integers associated with the members of the set P 1 j , where u is a constant or is a predefined function of the period of time.