ABSTRACT
For communications purposes, both sender and receiver using DES / DEA must know the same secret key, which can be used to encrypt and decrypt the message, or to generate and verify a Message Authentication Code (MAC). DES performs essentially only two opera tions on its input: Bit shifting and bit substitution. The key controls exact ly how this process works. Performing these operations repeatedly in a non-linear fashion eventually generates a result which cannot be used to retrieve the original without the key, a “one way function” that will be familiar to those acquainted with chaos theory. Through the successive application of simple operations a system can achieve a state of near total randomness, which leads to what every crypto aficionado is attempting to achieve - a message or file appearing so random that it is immune to easy decryption.
