Cryptography (or
cryptology) is derived from
Greek κρυπτός
kryptós "hidden," and the verb γράφω
gráfo "write". In modern times, it has become a branch of
information theory, as the
mathematical study of information and especially its transmission from place to place. The noted cryptographer
Ron Rivest has observed that "cryptography is about communication in the presence of adversaries." It is a central contributor to several fields:
information security and related issues, particularly,
authentication, and
access control. One of cryptography's primary purposes is hiding the meaning of messages, not usually the existence of such messages.
In modern times, cryptography also contributes to computer science. Cryptography is central to the techniques used in computer and network security for such things as access control and information confidentiality. Cryptography is also used in many applications encountered in everyday life; the security of ATM cards, computer passwords, and electronic commerce all depend on cryptography.
