By Hani AlQaffas

Cryptography is a technique used to hide the meaning of a message and is derived from the Greek word kryptos (hidden).

This is different from steganograhic techniques in that one is not hiding the actual message, only the meaning of the message.

If a message were to fall into the hands of the wrong person, cryptography should ensure that that message could not be read.

Typically the sender and receiver agree upon a message scrambling protocol beforehand and agree upon methods for encrypting and decrypting messages.

Cryptography is further divided into two implementation techniques and those include transposition and substitiution.

A standard DES encryption key is 56 bits long. Although considered very secure at the time of it's release in the mid 1970's, advancement in computer technology has assisted in the development of techniques to crack DES keys in meaningful time periods.

In 1999 a distributed computing project managed to crack a DES key in 22 hours and 15 minutes.

DES encryption is no longer considered strong enough for high security applications.

AES keys can be 128, 192 or 256 bits long. Most commonly the 128 bit key length is used - giving a total of 3.4 x 10^38 possible keys.

AES development has been a co-operative venture between the U.S. government and the private industry sector resulting in a encryption system that is royalty free.

Pretty Good Privacy (PGP) is a data encryption and decryption computer program that provides cryptographic privacy and authentication for data communication. PGP is often used for signing, encrypting and decrypting e-mails to increase the security of e-mail communications. It was created by Philip Zimmermann in 1991.

The idea of public-key cryptography was invented by Diffie and Hellman in 1976

They described a system for encoding and decoding messages where the ``key'' for encoding could be made publicly known without fear that the ``hidden key'' for decoding messages could be discovered

References

What is the difference between D.E.S. and A.E.S.?

What is the advantage of A.E.S. over D.E.S.?

How long can the bit be for A.E.S and D.E.S.?