Method of authenticating digital signature

A method of authenticating a digital signature is provided. The method includes sending a request from a first entity to a second entity, at least some of the request being digitally signed with a base key by the first entity, receiving, at the first entity, a digital signature and a bit-pattern from the second entity, the digital signature having been generated by the second entity using a variant key to digitally sign at least part of data indicative of a value stored in the second entity which 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 entity, generating, at the first entity, the variant key from the bit-pattern and the base key, and authenticating, at the first entity, the digital signature using the generated variant key. Only the first entity includes the base key and the second entity includes the variant key and the bit-pattern.