2. Mathematical Prelude to Cryptography
We will continue to describe Alice and Bob as two parties exchanging messages, and Eve as the eavesdropper. Alice sends either a character string or a binary string that constitutes her message to Bob. In mathematical terms we have the domain of the message. The message in question needs to be secured from the eavesdropper Eve; hence it needs to be encrypted.
Mapping or Function
The encryption of the message can be defined as mapping the message from the domain to its range such that the inverse mapping should recover the original message. This mapping is a mathematical construct known as the function.
So we have a domain, and the range of the function is defined such that the elements of the domain will always ...