Patent ID: 7953982

Claim:
A method of authenticating a digital signature comprising the steps of: sending a request from a first integrated circuit to a second integrated circuit, at least some of the request being digitally signed with a base key by the first integrated circuit; receiving, at the first integrated circuit, a digital signature and a bit-pattern from the second integrated circuit, the digital signature having been generated by the second integrated circuit using a variant key to digitally sign at least part of data indicative of a value stored in the second which integrated circuit is to be authenticated, the variant key being based on the result of applying a one way function to the base key and the bit-pattern; receiving the data at the first integrated circuit; generating, at the first integrated circuit, the variant key from the bit-pattern and the base key; and authenticating, at the first integrated circuit, the digital signature using the generated variant key, wherein only the first integrated circuit includes the base key and the second integrated circuit includes the variant key and the bit-pattern.