Introduction to stream ciphers

Abstract

The word cryptology comes from two Greek roots meaning “hidden” and “word”, and is the generic name used to describe the entire field of secret communications. Cryptology clearly splits into two opposite but complementary disciplines: cryptography and cryptanalysis. Cryptography seeks methods to ensure the secrecy of a confidential message, while cryptanalysis seeks to break such methods in order to recover the confidential message. In fact, the original message upon which the cryptographer applies the cryptographic transformation is called the plaintext message, or simply the plaintext. The result of this transformation is called the ciphertext message, or simply the ciphertext, or most often the cryptogram.