Abstract: The present invention relates in particular to a method for generating a digital signature (c, d) of a message M as well as a method for authenticating such a signature having the steps of defining a modulo N and a base g, a public key Y, and a private key x, these parameters N, g, Y, and x being linked by the relationship Y=gx (mod N), defining a hash function H the size of whose result has S bits, choosing a number r of T bits with T>=2S, calculating u from the following relationship u=gr*Yz where Z=2s, hashing the concatenation of M and u, by function H, the number thus obtained being the value c of the signature, and calculating the value d of the signature by the relationship: d=r+c*x.

Abstract: Encryption circuits and methods, in particular for smart cards, are disclosed. Smart cards without microprocessors may be authenticated very simply by using encryption with a secret card data table on which recursive cycles are executed. During each cycle, a word is read out of the table, said word being at an address that is at least partially defined by the word read out in the previous cycle. The new address preferably consists of several bits from the previous word and a bit from internal card data, external data supplied by a card reader, or a register containing a partial encryption result.