ABSTRACT
Whoever, in discussion, adduces authority uses not intellect but rather memory.
Leonardo da Vinci (1452-1519) Italian painter and designer
In this chapter, we will be concerned with authentication, meaning verification of the identity and data origin of a legitimate entity in a protocol by another (legitimate) entity. In this section, we will discuss impersonation (the assumption of the identity of a legitimate entity by an adversary) as well as identification and an introduction to digital signatures. We have already had a taste of a type of impersonation attack when we discussed the man-in-themiddle attack on page 27. The following is a description of such an attack on a general public-key cryptosystem.
