Ethical Hacking: Techniques, Tools, and Countermeasures, 4th Edition

Cryptographic Basics

As you learned in the introduction, cryptography can provide confidentiality, integrity, and even nonrepudiation. Cryptography is not new, and understanding legacy cryptographic techniques can help you understand how today’s techniques are used.

Several forms of cryptography have appeared throughout history. For example, during the Roman Empire, Julius Caesar used what is now a famous encryption cipher to communicate sensitive information with his generals. The so-called Caesar cipher is a shift cipher, which works by substituting each character in a message with the character a certain number of positions to the left or right of the current character—that is, by “shifting” the character. The Caesar cipher uses a key of ...