Chapter List

Introduction

Cryptography is covered in detail on the Security+ exam. Algorithms are the underlying foundation of cryptography, therefore this chapter looks at the basics of algorithms covering symmetric and asymmetric encryption and hashing concepts. This chapter then discusses the concepts of cryptography.

For as long as people have been writing down information, there has been the need to keep some information secret, either by hiding its existence or changing its meaning. The study of these methods is the science of cryptography. Encryption, a type of cryptography, refers to the process of scrambling information so that the casual observer cannot read it. What are algorithms and keys? An algorithm is a set of instructions for mixing and rearranging an original message, called plaintext, with a message key to create a scrambled message, referred to as ciphertext. Similarly, a cryptographic key is a piece of data used to encrypt plaintext to ciphertext, or ciphertext to plaintext, or both (depending on the type of encryption).

What does the word crypto mean? It has its origins in the Greek word kruptos, which means hidden. Thus, the objective of cryptography is to hide information so that only the intended recipient(s) can "unhide" it. In crypto terms, the hiding of information is called encryption, and when the information is unhidden, it is called decryption. A cipher is used to accomplish the encryption and decryption. Merriam-Webster's Collegiate...