GENERATOR AND METHOD OF GENERATING A SECRET-KEY PSEUDO-RANDOM FUNCTION

摘要

The invention relates to a generator of a pseudo-random function with secret key K from an input block of m bits to an output block of n bits using a determined number a of cryptographic schemes F1(m1, n1),..., Fi(mi, ni),..., Fa(ma,na) nested in layers according to a recursive structure, each current cryptographic scheme Fi(mi, ni) associating ni output bits with mi input bits in a number of rounds ri, each round using an internal elementary function f(i) constructed on the basis of ti cryptographic schemes Fi+1(mi+1,ni+1) from ni+1 bits, to mi+1 bits, with ni+1 ni,mi+1 mi and ti = 1, each cryptographic scheme Fi(mi, ni) defining a minimum number of operations comp(mi, ni, ri ), dependent on said number of rounds ri, required in order to distinguish it from a random function associating mi input bits ni output bits, the generator comprising calculation means (7) for calculating, for each cryptographic scheme Fi(mi, ni), said number of rounds ri so that said number of operations comp(mi, ni, ri ) associated therewith is greater than or equal to a predetermined number 2c, c being an integer.