Patent ID: 8542822
Filing Date: 2013-09-24
Classification: H04L,H04N

Abstract:
1. A method for renewing code, executable or interpretable by an electronic computer, for a cryptographic algorithm capable of enciphering a piece of data (D) by means of a key (K) to obtain a cryptogram (D*) or decipher a cryptogram (D*) by means of a key (K) to obtain a piece of unencrypted data (D), said code including at least N numerical constants, each numerical constant corresponding to an operand or to a mnemonic of an instruction of the code, a value of said numerical constants being independent of the piece of data (D), the key (K) and the cryptogram (D*), said method comprising: receiving a randomly drawn seed, the size of which, in terms of number of bits, is at least four times smaller than the number of bits needed to encode the N numerical constants of the cryptographic algorithm, expanding the seed deterministically to obtain a sequence of numbers, the sizes of which, in number of bits, are at least equal to the number of bits needed to encode the N numerical constants of the cryptographic algorithm, generating N new numerical constants from the sequence of numbers obtained, and replacing the N numerical constants of the code of the cryptographic algorithm by the N new numerical constants generated to obtain a code of a renewed cryptographic algorithm.