Patent ID: 7356842

Claim:
A cryptographic method implemented by a smart card of a set of smart cards each belonging to a first entity that may be different for each smart card, each smart card comprising a chip comprising storage means for storing a secret key and an identifier of the first entity that is the proprietor of the smart card and calculation means for executing a cryptographic algorithm comprising input arguments comprising at least the secret key, the method comprising: reading by the chip from a storage means of a second entity a list of identifiers in complete form of first entities that are smart card proprietors before any calculation is made by the calculation means of the chip, said list of identifiers being linked to a status assigned to each of the first entities by the second entity; and comparing by the chip the identifier stored in the storage means of the chip and the contents of the list of identifiers to authorize or prohibit calculations made by the calculation means of the chip as a function of the result of the comparison; simultaneous with reading the list of identifiers, reading by the chip signatures of each of the identifiers in the list of identifiers, a value of the number of identifiers in the list of identifiers, and a signature of the value from the storage means of the second entity, the signatures of each of the identifiers, the value, and the signature of the value having been previously calculated by a calculating means of the second entity; verifying by the chip the validity of each of the signatures of the identifiers and counting by the chip the number of identifiers in the list of identifiers before authorizing by the chip any calculations by the calculation means of the chip; and verifying by the chip that the counted number of identifiers and the read value of the number of identifiers are the same before authorizing by the chip any calculations by the calculation means of the chip.