title: Codes and Ciphers: An A to Z of Covert Communication, from the Clay Tablet to the Microdot
author:  Fred B. Wrixon 
description: This is a dictionary of people, terminology, events, code systems, and organizations related to cryptography. Easy-to-understand entries, with cross references, traces the development of codes and cyphers and the role they plaed in diplomatic, military, and business history. They also feature explanations of how to encrypt and decipher simple codes. Although international in scope, most of the entries concern the United States. The book features charts and a three-part bibliography of books, articles, and government documents, but having citations for suggested readings at the end of the main entries would have been useful. Suitable for anyone wanting general information on this fascinating field, this source is recommended for general reference collections; public libraries may also want a copy to circulate.<br /><i>- Daniel K. Blewett, Loyola Univ. Lib., Chicago</i><br />Copyright 1993 Reed Business Information, Inc.
zlib_text: ## Chapter 1  
  Foundations
  
  
  
  
  
  ### 1.1 Terminology
  
  
  **_Sender and Receiver_**
  
  
  Suppose a sender wants to send a message to a receiver. Moreover, this sender
  wants to send the message securely: She wants to make sure an eavesdropper
  cannot read the message.
  
  
  
  
  
  **_Messages and Encryption_**
  
  
  A message is **plaintext** (sometimes called cleartext). The process of
  disguising a message in such a way as to hide its substance is **encryption**.
  An encrypted message is **ciphertext**. The process of turning ciphertext back
  into plaintext is **decryption**. This is all shown in Figure 1.1.
  
  
  (If you want to follow the ISO 7498-2 standard, use the terms “encipher” and
  “decipher.” It seems that some cultures find the terms “encrypt” and “decrypt”
  offensive, as they refer to dead bodies.)
  
  
  The art and science of keeping messages secure is **cryptography** , and it is
  practiced by **cryptographers**. **Cryptanalysts** are practitioners of
  **cryptanalysis** , the art and science of breaking c