Patent ID: 7721108

Claim:
A method for checking a digital signature, involving a microcircuit connectable to a data processing system, the microcircuit being designed to receive requests to check digital signatures from the data processing system, and to process these requests, a digital signature being generated using a private key only known to a signatory entity and associated with a public key, said method comprising: a step of storing a certificates table containing a digest form of at least one public key in a memory in the microcircuit, wherein the public key is inserted into the certificates table by a step that comprises inserting, in the certificates table, a pointer to the digest form of the public key of the certification entity that issued the certificate of the public key, so as to define a certification tree in combination with the inserted digest form of the public key; and a phase of checking a digital signature comprising steps of: receiving by the microcircuit a digital signature to be checked and a public key in a pair of keys comprising a private key that was used to generate the digital signature to be checked; calculating a digest form of the received public key; searching for the calculated digest form of the public key in the microcircuit's certificates table, at a location at which the inserted pointer points; and decrypting the digital signature using the received public key if the calculated digest form of the public key is located in the certificates table.