Chapter 7: Cryptography - History of Cryptography

The first known use of cryptography can be dated back to 2000 B.C. in ancient Egypt. One of the earliest applications of cryptography was a hebrew method that replaced each letter of the alphabet with a different letter. We now have a term for this, and it is known as substitution cypher. Here is an example of this, with the letter 'A' being replaced with 'Z', 'B' being replaced with 'Y' and so on. So the word 'CRYPTOGRAPHY' would become 'XIBKGLTIZKSB'.  This is also known as a monoalphabetic substitution cypher because only one alphabet is used. If more than alphabet is used, it is then referred to as polyalphabetic. As time moved forward, algorithms were developed to improve methods of encryption. Today, there is the science of cryptanalysis, in which breaking down encryption is studied as well as reverse engineering the algorithms that encrypt data.