Encryption:

With the incredible growth of the Internet, a major concern has been how secure the Internet is, especially when you're sending sensitive information through 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. The most popular forms of security all rely on is encryption, the process of encoding information in such a way that only the person (or computer) with the key can decode it.
Most computer encryption systems belong in one of two categories:
• Symmetric-key encryption
• Public-key encryption

In symmetric-key encryption, each computer has a secret key (code) that it can use to encrypt a packet of information before it is sent over the network to another computer. Symmetric-key encryption is essentially the same as a secret code that each of the two computers must know in order to decode the information. The code provides the key to decoding the message.

Public-key encryption uses a combination of a private key and a public key. The private key is known only to your computer, while the public key is given by your computer to any computer that wants to communicate securely with it. To decode an encrypted message, a computer must use the public key, provided by the originating computer, and its own private key.
To implement public-key encryption on a large scale, such as a secure Web server might need, requires a different approach. This is where digital certificates come in. A digital certificate is basically a bit of information that says that the Web server is trusted by an independent source known as a certificate authority. The certificate authority acts as a middleman that both computers trust. It confirms that each computer is in fact who it says it is, and then provides the public keys of each computer to the other.
A popular implementation of public-key encryption is the Secure Sockets Layer (SSL). Originally developed by Netscape, SSL is an Internet security protocol used by Internet browsers and Web servers to transmit sensitive information. You will notice that the "http" in the address line is replaced with "https," and you should see a small padlock in the status bar at the bottom of the browser window.

In fact, sending information over a computer network is often much more secure than sending it any other way.