1. A system for authentication, encryption and/or signing, comprising: an input device designed by means of a given algorithm to extract predetermined characteristic values from a value input by a user, said value is specific to the user, wherein the predetermined characteristic values supplied exhibit a natural variation, said algorithm is designed to remove the natural variations in the predetermined characteristic values in order to yield an identical set of characteristic values on input of the corresponding predetermined characteristic values; and a device designed to generate at least one user specific encryption key comprising said characteristic values, wherein removing said natural variations comprises using a correction vector, said correction vector determined such that a value of a cutting vector corrected by said correction vector is disposed in the middle of a nearest interval.