Advanced Engineering Mathematics, 7th Edition

8.14 Cryptography

INTRODUCTION

The word cryptography is a combination of two Greek words: crypto, meaning “hidden” or “secret,” and grapho, which means “writing.” Cryptography then is the study of making “secret writings” or codes.

In this section we will consider a system of encoding and decoding messages that requires both the sender of the message and the receiver of the message to know:

• a specified rule of correspondence between a set of symbols (such as letters of the alphabet and punctuation marks from which messages are composed) and a set of integers; and
• a specified nonsingular matrix A.

Encoding/Decoding

A natural correspondence ...