# Outline of cryptography

The following outline is provided as an overview of and topical guide to cryptography:

Cryptography (or cryptology) – practice and study of hiding information. Modern cryptography intersects the disciplines of mathematics, computer science, and engineering. Applications of cryptography include ATM cards, computer passwords, and electronic commerce.

## Ciphers

Main article: Cipher

### Classical

• Monoalphabetic substitution –
• Scytale
• Grille
• Permutation
• VIC – complex hand cypher used by at least one Soviet spy in the early 1950s; it proved quite secure for the time

### Modern

Symmetric-key algorithms

• Stream ciphers
Main article: Stream ciphers
• Block ciphers
Main article: Block ciphers
Further information: Block cipher modes of operation
• CAST-256 (CAST6) – 128-bit block; the successor to CAST-128 and a candidate for the AES competition
• Polyalphabetic substitution machine cyphers
• Enigma – WWII German rotor cypher machine—many variants, any user networks for most of the variants
• Purple – highest security WWII Japanese Foreign Office cypher machine; by Japanese Navy Captain
• SIGABA – WWII US cypher machine by William Friedman, Frank Rowlett et al.
• TypeX – WWII UK cypher machine
• Hybrid code/cypher combinations
• JN-25 – WWII Japanese Navy superencyphered code; many variants
• Naval Cypher 3 – superencrypted code used by the Royal Navy in the 1930s and into WWII

Asymmetric key algorithms

• ACE-KEMNESSIE selection asymmetric encryption scheme; IBM Zurich Research)
• ECIESElliptic Curve Integrated Encryption System, Certicom Corporation
• ECIES-KEM
• ECDHElliptic Curve Diffie-Hellman key agreement, CRYPTREC recommendation

## Keys

Main article: Key (cryptography)

Authentication

Main article: Key authentication

Transport/exchange

Weak keys

Main article: Weak key

## Cryptographic hash functions

• MD5 – one of a series of message digest algorithms by Prof Ron Rivest of MIT; 128 bit digest
• SHA-1 – developed at NSA 160-bit digest, an FIPS standard; the first released version was defective and replaced by this; NIST/NSA have released several variants with longer 'digest' lengths; CRYPTREC recommendation (limited)

## Cryptanalysis

Main article: Cryptanalysis

Classical

Modern

• Symmetric algorithms
• Hash functions:
• Network attacks
• External attacks

## Organizations and selection projects

Standards

• Federal Information Processing Standards Publication Program – run by NIST to produce standards in many areas to guide operations of the US Federal government; many FIPS publications are ongoing and related to cryptography
• ANSI – standardization process that produces many standards in many areas; some are cryptography related, ongoing)
• ISO – standardization process produces many standards in many areas; some are cryptography related, ongoing
• IEEE – standardization process produces many standards in many areas; some are cryptography related, ongoing
• IETF – standardization process that produces many standards called RFCs) in many areas; some are cryptography related, ongoing)

General cryptographic

• NSA – internal evaluation/selections, charged with assisting NIST in its cryptographic responsibilities
• GCHQ – internal evaluation/selections, a division is charged with developing and recommending cryptographic standards for the UK government
• DSD – Australian SIGINT agency, part of ECHELON
• Communications Security Establishment (CSE) – Canadian intelligence agency

Open efforts

• DESNBS selection process, ended 1976
• RIPE – division of the RACE project sponsored by the European Union, ended mid-1980s
• AES – a "break-off" competition sponsored by NIST, ended in 2001
• NESSIE Project – an evaluation/selection program sponsored by the European Union, ended in 2002
• eSTREAM– program funded by ECRYPT; motivated by the failure of all of the stream ciphers submitted to NESSIE, ended in 2008
• CRYPTREC – evaluation/recommendation program sponsored by the Japanese government; draft recommendations published 2003
• Internet Engineering Task Force – technical body responsible for Internet standards— the Request for Comment series is ongoing
• CrypTool – an e-learning freeware programme in English and German— exhaustive educational tool about cryptography and cryptanalysis