Method for improving a random generator to make it resistant against attacks by measurement of current

The invention concerns a modification of two methods for random number generation to make them more resistant to attacks by current measuring. It is particularly designed to be implemented in electronic devices such as smart cards, PCMCIA, badges, contactless cards or any other portable device. It consists in: encrypting with the DES algorithm using the key K a value D representing a date information and introducing the result in an integer variable I; 2) for j ranging from 1 to m: 2a) substituting s with s x or I; 2b) introducing in the integer variable y the result of the encryption of s with the DES algorithm using the key K; 2c) introducing in xj the result of y or s; 2d) substituting s with y x or I; 2e) introducing in s the result of the encryption of s with the DES algorithm using the key K; 3) restoring in output the sequence (x1, x2, , xm).