The purpose of this article is to provide information in the area of practical cryptography of interest to anyone wishing to use cryptographic software. I have mostly avoided discussion of technical matters in favor of a more general explanation of what I regard as the main things to be understood by someone beginning to use encryption. Those wishing to get more deeply into the theoretical aspects should consult Bruce Schneier´s book (see bibliography at end).
Cryptography is the art or science of secret writing, or more exactly, of storing information (for a shorter or longer period of time) in a form which allows it to be revealed to those you wish to see it yet hides it from all others. A cryptosystem is a method to accomplish this. Cryptanalysis is the practice of defeating such attempts to hide information. Cryptology includes both cryptography and cryptanalysis.
The original information to be hidden is called “plaintext”. The hidden information is called “ciphertext”. Encryption is any procedure to convert plaintext into ciphertext. Decryption is any procedure to convert ciphertext into plaintext.
A cryptosystem is designed so that decryption can be accomplished only under certain conditions, which generally means only by persons in possession of both a decryption engine (these days, generally a computer program) and a particular piece of information, called the decryption key, which is supplied to the decryption engine in the process of decryption.Read Full Story