Orange

France Telecom

Ryad Benadjila

Olivier Billet

Stanislas Francfort

Alain Nochimowski

Haythem Gadacha

A method and system for a user to obtain a derived value Kof m bits, in which, given two pseudo-random functions gand gfrom 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 K=g&#x2218; . . . g&#x2218;g(S), where, for i=, . . . , n, g=gif r, and g=gif r, 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 U, where j=, . . . , p, recorded in a table Tand equal to U=g&#x2218; . . . g&#x2218;g(S), where, for i=, . . . , l(j), the indices vare predetermined bits, for a word Uequal to U=g&#x2218; . . . g&#x2218;g(S); said derived value Kis thereafter obtained by calculating K=g&#x2218; . . . g(U). Application to the encryption/decryption of pay-per-use digital contents, and to authentication.

Traceable method and system for broadcasting digital data

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 Vassociated 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 Vcomprises 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 V

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Paris, France

Ryad Benadjila