Cryptography

Cryptography (or cryptology; derived from Greek κρύπτω krýpto "hidden" and the verb γράφω gráfo "to write" or λέγειν legein "to speak") is the practice and study of hiding information. In modern times, cryptography is considered to be a branch of both mathematics and computer science, and is affiliated closely with information theory, computer security, and engineering. Cryptography is used in applications present in technologically advanced societies; examples include the security of ATM cards, computer passwords, and electronic commerce, which all depend on cryptography. Until modern times, cryptography referred almost exclusively to encryption, the process of converting ordinary information (plaintext) into unintelligible gibberish (i.e., ciphertext). Decryption is the reverse, moving from unintelligible ciphertext to plaintext. A cipher (or cypher) is a pair of algorithm which creates the encryption and the reversing decryption. The detailed operation of a cipher is controlled... full article at wikipedia