HTTP: The Definitive Guide

Digital Cryptography

Before we talk in detail about HTTPS, we need to provide a little background about the cryptographic encoding techniques used by SSL and HTTPS. In the next few sections, we’ll give a speedy primer of the essentials of digital cryptography. If you already are familiar with the technology and terminology of digital cryptography, feel free to jump ahead to Section 14.7.

In this digital cryptography primer, we’ll talk about:

Ciphers

Algorithms for encoding text to make it unreadable to voyeurs

Keys

Numeric parameters that change the behavior of ciphers

Symmetric-key cryptosystems

Algorithms that use the same key for encoding and decoding

Asymmetric-key cryptosystems

Algorithms that use different keys for encoding and decoding

Public-key cryptography

A system making it easy for millions of computers to send secret messages

Digital signatures

Checksums that verify that a message has not been forged or tampered with

Digital certificates

Identifying information, verified and signed by a trusted organization

The Art and Science of Secret Coding

Cryptography is the art and science of encoding and decoding messages. People have used cryptographic methods to send secret messages for thousands of years. However, cryptography can do more than just encrypt messages to prevent reading by nosy folks; it also can be used to prevent tampering with messages. Cryptography even can be used to prove that you indeed authored a message or transaction, just like your handwritten signature on a check ...