Secret Key Cryptography

2 What is cryptography?

This chapter covers

• Basic terms used in cryptography
• What is an unbreakable cipher?
• What are the different types of cryptography?

Cryptography is often called “The Art of Secret Writing.” It is more than that. It encompasses everything from invisible inks to transmitting messages by quantum entanglement of photons. In particular, cryptography includes the making and breaking of codes and ciphers.

Different authors use cryptographic terminology in inconsistent ways, so let us begin by agreeing on some basic terms.

Plaintext or cleartext is the message or document that you wish to keep secret. In traditional cryptography, the message was text written in some language known to both sender and receiver. In a computer setting, ...