PUF PROTOCOL WITH IMPROVED BACKWARD SECURITY

摘要

The present invention relates to a physical token (102), a method of authenticating a physical token (102) and a device (104) for authenticating a physical token. A basic idea of the present invention is to provide a protocol for secure data exchange between two parties, and in particular for authenticating a physical token, such as a smart card comprising a physical unclonable function (PUF), in which protocol a cryptographic key is used which cannot be traced back in time, because the key is obtained by means of a noninvertible function, i.e. a one-way function. The parties may e.g. comprise a verifying party in the form of a bank with which a cash withdrawal is to be effected and a party to be authenticated, which are embodied by an ATM withdrawal card to which a user has access.