Wednesday, December 24, 2008

Security Encryption Systems

Security Encryption Systems

Computer encryption is based on the science of cryptography, which has been used as long as humans have wanted to keep information secret. Before the digital age, the biggest users of cryptography were governments, particularly for military purposes.
An encrypted document is surrounded by an array of commercially available encryption products at the FBI office in Washington, D.C.
Scott J. Ferrell/Congressional Quarterly/Getty Images
An encrypted document is surrounded by an array of commercially available encryption products at the FBI office in Washington, D.C.

The Greek historian Plutarch wrote, for example, about Spartan generals who sent and received sensitive messages using a scytale, a thin cylinder made out of wood. The general would wrap a piece of parchment around the scytale and write his message along its length. When someone removed the paper from the cylinder, the writing appeared to be a jumble of nonsense. But if the other general receiving the parchment had a scytale of similar size, he could wrap the paper around it and easily read the intended message.

The Greeks were also the first to use ciphers, specific codes that involve substitutions or transpositions of letters and numbers. Here's an example of a typical cipher, with a grid of letters and their corresponding numbers:

1 2
1 A B
2 F G H I/J K
3 L M N O P
4 Q R S T U
5 V W X Y Z

If a Spartan general wished to send the message I AM SPARTA to another general, he would write this series of numbers:

42 11 23 34 53 11 24 44 11

As long as both generals had the correct cipher, they could decode any message the other sent. To make the message more difficult to decipher, they could arrange the letters inside the grid in any combination.

Most forms of cryptography in use these days rely on computers, simply because a human-based code is too easy for a computer to crack. Ciphers are also better known today as algorithms, which are the guides for encryption -- they provide a way in which to craft a message and give a certain range of possible combinations. A key, on the other hand, helps a person or computer figure out the one possibility on a given occasion.

Computer encryption systems generally belong in one of two categories:

* Symmetric-key encryption
* Public-key encryption

In the following sections, you'll learn about each of these systems.


When we use the Internet, we're not always just clicking around and passively taking in information, such as reading news articles or blog posts -- a great deal of our time online involves sending others our own information. Ordering something over the Internet, whether it's a book, a CD or anything else from an online vendor, or signing up for an online account, requires entering in a good deal of sensitive personal information. A typical transaction might include not only our names, e-mail addresses and physical address and phone number, but also passwords and personal identification numbers (PINs). ­

The incredible growth of the Internet has excited businesses and consumers alike with its promise of changing the way we live and work. It's extremely easy to buy and sell goods all over the world while sitting in front of a laptop. But security is a major concern on the Internet, especially when you're using it to send sensitive information between parties.

Let's face it, there's a whole lot of information that we don't want other people to see, such as:

* Credit-card information
* Social Security numbers
* Private correspondence
* Personal details
* Sensitive company information
* Bank-account information

information security is provided on computers and over the Internet by a variety of methods. A simple but straightforward security method is to only keep sensitive information on removable storage media like portable flash memory drives or external hard drives. But the most popular forms of security all rely on encryption, the process of encoding information in such a way that only the person (or computer) with the key can decode it.

In this article, you will learn about encryption and authentication. You will also learn about public-key and symmetric-key systems, as well as hash algorithms.