Half a Loaf is Better than None: Some Novel Message Integrity Problems

The familiar failing of digital signatures formed using an individual´s private key in a public key cryptosystem is that the signature can be disavowed, in the sense that an impartial arbiter cannot prove otherwise, by the holder of the Private key either disclosing, or claiming, the disclosure of his key. In various guises this failure characterizes all individual identification systems which equate identity with the possession of a piece of information that was once known to be in the private possession of the individual identified. This paper describes a means of associating an individual with an unforgeable piece of information, such that the association is feasible to verify whenever the individual needs to be identified. Consequently, the bearer canbe identified (associated) with the information and the problem described above solved. An application of this principle to access control at sensitive nuclear facilities has been made and is described briefly.