This glossary lists types of keys as the term is used in cryptography, as opposed to door locks. Terms that are primarily used by the U.S. National Security Agency are marked (NSA). For classification of keys according to their usage see cryptographic key types. A key is a piece of information that controls the operation of a cryptography algorithm. ... Cryptography has had a long and colourful history. ... A number of different keys A single key A key is a device which is used to open a lock. ... NSA seal The National Security Agency / Central Security Service (NSA/CSS) is the largest United States government intelligence agency. ... According to NIST SP 800-57 the following types of keys should be considered: Private signature key Private signature keys are the private keys of asymmetric (public) key pairs that are used by public key algorithms to generate digital signatures with possible long-term implications. ...

• 40-bit key - key with a length of 40 bits, once the upper limit of what could be exported from the U.S. and other countries without a license. Considered very insecure. See key size for a discussion of this and other lengths.

• authentication key - Key used in a keyed-hash message authentication code, or HMAC.

• benign key - (NSA) a key that has been protected by encryption or other means so that it can be distributed without fear of its being stolen. Also called BLACK key.

• cryptovariable - NSA calls the output of a stream cipher a key or key stream. It often uses the term cryptovariable for the bits that control the stream cipher, what the public cryptographic community calls a key.

• derived key - keys computed by applying a predetermined hash algorithm or key derivation function to a password or, better, a passphrase.

• electronic key - (NSA) key that is distributed in electronic (as opposed to paper) form. See EKMS.

• ephemeral key - A key that only exists within the lifetime of a communication session.

• expired key - Key that was issued for a use in a limited time frame (cryptoperiod in NSA parlance) which has passed and, hence, the key is no longer valid.

• key encryption key (KEK) - key used to protect other keys (e.g. TEK, TSK).

• key fill - (NSA) loading keys into a cryptographic device. See AN/CYZ-10.

• FIREFLY key - (NSA) keys used in an NSA system based on public key cryptography.

• master key - key from which all other keys (or a large group of keys) can be derived. Also a physical key that can open all the doors in a building.

• one-time pad - keying material that is as long as the plaintext and only used once. See one-time pad article.

• paper key - (NSA) keys that are distributed in paper form, such as printed lists of settings for rotor machines, or keys in punch card or paper tape formats. Paper key is easily coped. See Walker spy ring, RED key.

• poem key - Keys used by OSS agents in World War II in the form of a poem that was easy to remember. See Leo Marks.

• Public/private key - in public key cryptography, separate keys are used to encrypt and decrypt a message. The encryption key (public key) need not be kept secret and can be published. The decryption or private key must be kept secret to maintain confidentiality. Public keys are often distributed in a signed public key certificate.

• pre-placed key - (NSA) large numbers of keys (perhaps a year's supply) that are loaded into an encryption device allowing frequent key change without refill.

• RED key - (NSA) symmetric key in a format that can be easily copied, e.g. paper key or unencrypted electronic key. Opposite of BLACK or benign key.

• revoked key - a public key that should no longer be used, typically because its owner is no longer in the role for which it was issued or because it may have been compromised. Such keys are placed on a certificate revocation list or CRL.

• session key - key used for one message or an entire communications session. See traffic encryption key.

• symmetric key - a key that is used both to encrypt and decrypt a message. Symmetric keys are typically used with a cipher and must be kept secret to maintain confidentiality.

• traffic encryption key (TEK) - a symmetric key that is used to encrypt messages. TEKs are typically changed frequently, in some systems daily and in others for every message. See session key.

• transmission security key (TSK) - (NSA) seed for a pseudorandom number generator that is used to control a radio in frequency hopping or direct-sequence spread spectrum modes. See SINCGARS, electronic warfare.

• seed key - (NSA) a key used to initialize a cryptographic device so it can accept operational keys using benign transfer techniques. Also a key used to initialize a pseudorandom number generator to generate other keys.

• signature key - public key cryptography can also be used to electronically sign messages. The private key is used to create the electronic signature, the public key is used to verify the signature. Separate public/private key pairs must be used for signing and encryption. The former is called signature keys.

• stream key - the output of a stream cipher as opposed to the key (or cryptovariable in NSA parlance) that controls the cipher

• training key - (NSA) unclassified key used for instruction and practice exercises.

• Type 1 key - (NSA) keys used to protect classified information. See Type 1 product.

• Type 2 key - (NSA) keys used to protect sensitive but unclassified (SBU) information. See Type 2 product.

• Vernam key - Type of key invented by Gilbert Vernam in 1918. See stream key.

• zeroized key - key that has been erased.

40-bit encryption is a key size for symmetric encryption representing a low-level of security where the key is forty bits in length (five bytes). ... In cryptography, the key size (alternatively key length) is a measure of the number of possible keys which can be used in a cipher. ... A keyed-hash message authentication code, or HMAC, is a type of message authentication code (MAC) calculated using a cryptographic hash function in combination with a secret key. ... The operation of A5/1, a LFSR-based stream cipher used to encrypt mobile phone conversations. ... A key is a piece of information that controls the operation of a cryptography algorithm. ... A hash function is a function that converts an input from a (typically) large domain into an output in a (typically) smaller range (the hash value, often a subset of the integers). ... A Key derivation function or key stretcher is a cryptographic hash function which is designed to make a key or password harder to attack using a precomputed dictionary attack or brute force attack. ... A password is a form of secret authentication data that is used to control access to a resource. ... A passphrase is a sequence of words or other text used to control access to a computer system, program or data. ... The Electronic Key Management System (EKMS) system is an National Security Agency led program responsible for Communications Security (COMSEC) key management, accounting and distribution. ... AN/CYZ-10 The AN/CYZ-10, or Data Transfer Device (DTD) is an NSA-developed, portable, hand-held device capable of securely receiving, storing, and transferring data between compatible cryptographic and communications equipment. ... Public key cryptography is a form of cryptography which generally allows users to communicate securely without having prior access to a shared secret key, by using a pair of cryptographic keys, designated as public key and private key, which are related mathematically. ... A number of different keys A single key A key is a device which is used to open a lock. ... The plain text term has a different meaning. ... Excerpt from a one time pad. ... In cryptography, a rotor machine is a electro-mechanical device used for encrypting and decrypting secret messages. ... The punch card (or Hollerith card) is a recording medium for holding information for use by automated data processing machines. ... A roll of punched tape Punched tape is an old-fashioned form of data storage, consisting of a long strip of paper in which holes are punched to store data. ... John Anthony Walker Junior, born July 28, 1937, was a Chief Warrant Officer and communications specialist for the U.S. Navy, who sold his services as a spy to the Soviet Union from 1967 to 1985, the height of the Cold War era. ... OSS may refer to any of the following: Office of Strategic Services, forerunner of the CIA Open Sound System Open-source software Operations Support System Operations Support Squadron Out of School Suspension Optimized Systems Software The Old Syriac Sinaiticus OSS was the name of an ITC Entertainment TV series which... Combatants Allied Powers Axis Powers Commanders {{{commander1}}} {{{commander2}}} Strength {{{strength1}}} {{{strength2}}} Casualties 37 million Civilians 25 million military World War II, also known as the Second World War, was a mid-20th century conflict that engulfed much of the globe and is accepted as the largest and deadliest war in... Leo Marks at the opening of the Violette Szabo Museum, Wormelow Leopold Samuel Marks (September 24, 1920 - January 15, 2001) was an English cryptographer and scriptwriter. ... Public key cryptography is a form of cryptography which generally allows users to communicate securely without having prior access to a shared secret key, by using a pair of cryptographic keys, designated as public key and private key, which are related mathematically. ... In cryptography, a public key certificate (or identity certificate) is a certificate which uses a digital signature to bind together a public key with an identity — information such as the name of a person or an organization, their address, and so forth. ... In the operation of some cryptosystems, usually PKIs, a certificate revocation list (CRL) is a list of certificates (more accurate: their serial numbers) which have been revoked, are no longer valid, and should not be relied upon by any system user. ... A session key is a key used for encrypting and signing a group of messages in a communication session. ... A pseudorandom number generator (PRNG) is an algorithm that generates a sequence of numbers, the elements of which are approximately independent of each other. ... Frequency-hopping spread spectrum (FHSS) is a spread-spectrum method of transmitting signals by rapidly switching a carrier among many frequency channels, using a pseudorandom sequence known to both transmitter and receiver. ... In telecommunication, the term direct-sequence spread spectrum has the following meanings: A system (a) for generating spread-spectrum transmissions by phase-modulating a sine wave pseudorandomly with a continuous string of pseudonoise code symbols, each of duration much smaller than a bit and (b) that may be time-gated... SINCGARS stands for Single Channel Ground and Airborne Radio System. ... Electronic warfare (EW) has three main components: Electronic Attack (EA) This is the active use of the electromagnetic spectrum to deny its use by an adversary. ... A pseudorandom number generator (PRNG) is an algorithm that generates a sequence of numbers, the elements of which are approximately independent of each other. ... Public key cryptography is a form of cryptography which generally allows users to communicate securely without having prior access to a shared secret key, by using a pair of cryptographic keys, designated as public key and private key, which are related mathematically. ... The operation of A5/1, a LFSR-based stream cipher used to encrypt mobile phone conversations. ... Classified information is secret information to which access is restricted by law or corporate rules to a particular hierarchical class of people. ... Classified information is secret information to which access is restricted by law or corporate rules to a particular hierarchical class of people. ... In cryptography, a Type 1 product is a device or system certified by the National Security Agency (NSA) for use in cryptographically securing classified U.S. Government information. ... In cryptography, Type 2 products are unclassified cryptographic equipment, assemblies, or components, endorsed by the National Security Agency (NSA), for use in telecommunications and automated information systems for the protection of national security information. ... Gilbert Sandford Vernam (1890–7 February 1960) was a AT&T Bell Labs engineer who, in 1917, invented the stream cipher and later co-invented the one-time pad cipher. ... 1918 (MCMXVIII) was a common year starting on Tuesday of the Gregorian calendar (see link for calendar) or a common year starting on Wednesday of the Julian calendar. ...

See also

• Specific encryption systems and ciphers have key types associated with them, e.g. PGP key, DES key, AES key, RC4 key, BATON key, Kerberos key, etc.
• Category:Cryptographic algorithms
• Category:Cryptographic protocols