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How does encryption really work?

What is encrytion? How does it work? How is it done? Can you give me examples?
The purpose for encryption (you might hear it referred to as cryptography) is to convert human readable information into something unreadable (decryption is by definition the reverse). The reason we use encryption is to convert perhaps private/sensitive information into a form that only a person who knows how to decrypt it can read it. For instance, you might want to order something on the Internet using your credit card, but when you transmit the number, you do not want just anyone to read it. So you encrypt it, send it to the vendor, and assuming they have the method to decrypt it, they can then read it.

There are two basic forms of encryption are symmetric and asymmetric cryptography. In symmetric encryption, the same special "key" is used to encrypt and decrypt the data. In asymmetric encryption there are two keys, the public key and the private key, that are used by the sender and receiver.

Examples of symmetrical encryption include DES (data encryption standard), Triple DES, and the Rijndael Cipher (pronounced rain-del). Examples of asymmetrical encryption include RSA, Diffie-Hellman, and El Gamal. A good reference book for encryption technologies is "Applied Cryptography" by Bruce Schneier.

This was first published in December 2001

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