Patent ID: 8837719

Claim:
A cryptographic method by a pseudo-random generator of generating a current value for a state vector of size k corresponding to a current iteration of a pseudo-random data sequence formed by a succession of values for the state vector generated iteratively from an initial value of the state vector, the method comprising: obtaining, with a processing device, a current intermediate value calculated from a preceding value of the state vector generated in a previous iteration; forming, with the processing device, a permutation key by selecting d bits from a first intermediate vector of size k, wherein d is less than or equal to k and the first intermediate vector is formed from the preceding value of the state vector in which a section has been replaced by the current intermediate value; determining, with the processing device, d permutations, each of size k 1 , as a function at least of the value of a respective associated bit of the permutation key; successively applying, with the processing device, each of the permutations to a provisional vector of size k 1 to determine a result vector, wherein k 1 is greater than or equal to k and the provisional vector includes the first intermediate vector; and determining, with the processing device, the current value of the state vector from at least one section of said result vector.