A Survey of Information AuthenticationThis work was performed at Sandia National Laboratories and supported by the u.s. Department of Energy under contract no. DEAC0476DP00789.

In both commercial and private transactions, authentication of information (messages) is of vital concern to all of the participants. For example, the party accepting a check usually insists on corroborating identification of the issuer - authentication of the originator, or as we shall say throughout this chapter, the transmitter - and the party issuing the check not only fils in the face amount in numerals, but also writes out the amount in script, and may even go so far as to emboss that part of the check to make it more difficult for anyone to subsequently alter the face amount appearing on an instrument bearing his valid signature, that is, a primitive means of providing for the later authentication of the communication or message. Although this example illustrates the two main concerns of the participants in the authentication of information, namely, the verification that the communication was originated by the purported transmitter and that it hasn't subsequently been substituted for or altered, it fails to illustrate perhaps the most important feature in the current use of authentication. The information conveyed on the check is inextricably linked to a physical instrument, the check itself, for which there exist legally accepted protocols to establish the authenticity of the signature and the integrity of what the issuer wrote in the event of a later dispute as to whether the check is valid or the signature genuine, independent of the information content (date, amount, etc.) recorded there. The contemporary concern in authentication, though, is with situations in which the exchange involves only information, that is, in which there is no physical instrument that can later be used to corroborate the authenticity of either the transmitter's identity or of the communication.