Cryptography

Cryptography is an interdisciplinary subject, drawing from several fields. Older forms of cryptography were chiefly concerned with patterns in language. More recently, the emphasis has shifted, and cryptography makes extensive use of mathematics, particularly discrete mathematics, including topics from number theory, information theory, computational complexity, statistics and combinatorics. Cryptography is also considered a branch of engineering, but it is considered to be an unusual one as it deals with active, intelligent and malevolent opposition (see cryptographic engineering and security engineering). Cryptography is a tool used within computer and network security.

Other topics

See also: Topics in cryptography

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The security of all practical encryption schemes remains unproven, both for symmetric and asymmetric schemes. For symmetric ciphers, confidence gained in an algorithm is usually anecdotal — e.g. no successful attack has been reported on an algorithm for several years despite intensive analysis. Such a cipher might also have provable security against a limited class of attacks. For asymmetric schemes, it is common to rely on the difficulty of the associated mathematical problem, but this, too, is not provably secure.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Cryptography has a cipher with a strong proof of security: the one-time pad. However, it requires keys (at least) as long as the plaintext, so it is widely considered too cumbersome to use in practice.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

When the security of a system fails, it is rare that a weakness in the cryptographic algorithms is exploited. More often, it is a mistake in the implementation, the protocols used or some other human error. The study of how best to implement and integrate cryptography is a field in itself, see: cryptographic engineering, security engineering and cryptosystem.

Related Topics:
Cryptographic engineering - Security engineering - Cryptosystem

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Cryptography can be used to implement various protocols: zero-knowledge proof, secure multiparty computation and secret sharing, for example.

Related Topics:
Protocols - Zero-knowledge proof - Secure multiparty computation - Secret sharing

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Cryptography can be used to implement digital rights management.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~