ABSTRACT
This chapter shows that some of the techniques used to give the recipient of a message confidence in: the identity of the originator of a message; the fact that the contents of the message have not been altered; and the fact that the sender will not be able to deny sending the message. It considers digital signatures and discusses how effective they might be in replacing the traditional hand-written signatures. A digital signature is usually represented as a string of bits. It may be appended to a message or the message may form an integral part of it. Digital signatures provide one of the most natural applications for public key systems, notably RSA and El Gamal. The solution to the message integrity problem is perfectly acceptable provided that the participants have faith in their ability to keep the key value secret and provided there is never a dispute between the sender and receiver.
