Patent ID: 7590846

Claim:
An asymmetrical cryptographic method for protecting a hard-wired electronic logic chip against fraud in transactions between the hard-wired electronic chip and an application, including calculating an authentication value V from input parameters in the electronic chip, said method comprising the steps of: producing at least one pseudo-random number r at the application before the hard-wired electronic chip is placed into circulation; calculating, at the application before the hard-wired electronic chip is placed into circulation, parameters x corresponding to the at least one pseudo random number r, each corresponding parameter x being linked to the pseudo random number r by a mathematical relationship; storing the corresponding parameter x in a data memory of the electronic chip before the hard-wired electronic chip is placed into circulation; producing, at the chip, the pseudo-random number r specific to the transaction via a serial pseudo-random generator included in the hard-wired electronic chip, said hard-wired electronic chip reading the stored corresponding parameter x calculated by the application before the hard-wired electronic chip is placed into circulation; sending from the hard-wired electronic chip to the application the corresponding parameter x calculated by the application, before the hard-wired electronic chip is placed into circulation, which is linked to the pseudo-random number r by the mathematical relationship and stored in the data memory of the hard-wired electronic chip; calculating, at the hard-wired electronic chip, a parameter y constituting an entire or a portion of the authentication value V via a serial function whose input parameters are at least the random number r specific to the transaction and a private key s belonging to an asymmetrical pair of keys; sending the authentication value V from the hard-wired electronic chip to the application; and verifying, at the application, said authentication value V via a verification function whose input parameters consist of public parameters including at least a public key p.