A natural taxonomy for digital information authentication schemes

Abstract

There are two objectives that prompt the authentication of information; one is to verify that the information was, in all probability, actually originated by the pur- ported originator, i.e., source identification, the other is to verify the integrity of the information, i.e., to establish that even if the message was originated by the authorized source, that it hasn’t been subsequently altered, repeated, delayed, etc. These two objectives are normally treated in the theory of authentication as though they are inseparable, and will also be treated in that way here, although recent results by Cham [l] demonstrating message integrity with source anonymity and by Fiat and Shamir [Z], by Goldreich, Micali and Wigderson [3], and by others demon- strating verification of source identity with no additional information exchange show that the functions can in some instances be separated. The relevance of this comment to the subject matter of this paper is that it suggests that there may be a fourth independent coordinate in information authentication besides the three that will be discussed here. In spite of considerable effort, we have been unable to produce a convincing argument for or against this being the case, so we only mention the possibility for completeness.