Cryptographic method of protecting an electronic chip against fraud

A device (24) including an electronic chip (23) and means for executing a cryptographic method of protecting the electronic chip against fraud in transactions between an application (25) and the electronic chip by calculating (27) a certificate (S) from input parameters (Em) in the electronic chip, which device is characterized in that it includes:

• mixing means for mixing some or all of the input parameters (Em) to supply an output data item E′=(e′1, e′2, . . . , e′n, . . . , e′N) resulting from said mixing,
• a finite state automaton that changes from an old state to a new state in accordance with a function depending at least on the old state and a value from the series of bits (e′1, e′2, . . . , e′n, . . . , e′N), and
• output means for calculating the certificate (S) from input arguments including at least one state of the automaton.