Abstract: A method and system for a user to obtain a derived value Kr of m bits, in which, given two pseudo-random functions g0 and g1 from m bits to m bits, said user obtains, on the basis of an input parameter consisting of a word r of n bits, a derived value Kr=grn? . . . gr2?gr1 (S), where, for i=1, . . . , n, gri=g0 if ri=0, and gri=g1 if ri=1, and where S is a master value of m bits which is not disclosed to said user. This method comprises the following steps: a search is conducted, from among a set of words of m bits Uj, where j=1, . . . , p, recorded in a table TU and equal to Uj=gvl(j)(j)? . . . gv2(j)?gv1(j) (S), where, for i=1, . . . , l(j), the indices vi(j) are predetermined bits, for a word U? equal to U?=grl(?)? . . . gr2?gr1 (S); said derived value Kr is thereafter obtained by calculating Kr=grn? . . . grl(?)+1 (U?). Application to the encryption/decryption of pay-per-use digital contents, and to authentication.

Abstract: The invention relates to a method of coupling a computer program and/or data to a reference system, implementation of the computer program and/or access to the data being carried out by executing software, a group of parameters being associated with the reference system. The method comprises the protection of a value V0 associated with the reference system and necessary for the execution of said software, in alliance with at least one parameter of said group of parameters. The protection of the value V0 comprises the storage of at least one data pair comprising a function g_i of at least one parameter of said group of parameters and a function h_i of the value V0.

Abstract: A method and system for a user to obtain a derived value Kr of m bits, in which, given two pseudo-random functions g0 and g1 from m bits to m bits, said user obtains, on the basis of an input parameter consisting of a word r of n bits, a derived value Kr=grn? . . . gr2?gr1 (S), where, for i=1, . . . , n, gri=g0 if ri=0, and gri=g1 if ri=1, and where S is a master value of m bits which is not disclosed to said user. This method comprises the following steps: a search is conducted, from among a set of words of m bits Uj, where j=1, . . . , p, recorded in a table TU and equal to Uj=gvl(j)(j)? . . . gv2(j)?gv1(j) (S), where, for i=1, . . . , l(j), the indices vi(j) are predetermined bits, for a word U? equal to U?=grl(?)? . . . gr2?gr1 (S); said derived value Kr is thereafter obtained by calculating Kr=grn? . . . gr1(?)+1 (U?). Application to the encryption/decryption of pay-per-use digital contents, and to authentication.

Abstract: The invention relates to a method of coupling a computer program and/or data to a reference system, implementation of the computer program and/or access to the data being carried out by executing software, a group of parameters being associated with the reference system. The method comprises the protection of a value V0 associated with the reference system and necessary for the execution of said software, in alliance with at least one parameter of said group of parameters. The protection of the value V0 comprises the storage of at least one data pair comprising a function g_i of at least one parameter of said group of parameters and a function h_i of the value V0.