Publisher Summary Traditionally, cryptography has consisted of any means possible whereby communications may be encrypted and transmitted. This could be as simple as using a language with which the opposition is not familiar. Since the beginning of sentient language, cryptography has been a part of communication. It is as old as language itself. In fact, one could make the argument that the desire and ability to encrypt communication, to alter a missive in such a way so that only the intended recipient may understand it, is an innate ability hardwired into the human genome. Aside from the necessity to communicate, it could very well be what led to the development of language itself. Computer-based cryptography is the art of creating a form of communication that can be readily understood by the intended recipients, cannot be understood by unintended recipients, and can be adapted and changed easily with relatively small modifications, such as a changed passphrase or word. For most information technology occupations, knowledge of cryptography is a very small part of a broader skill set, and is generally limited to relevant application.