K

Kerberos

A trusted third-party authentication protocol developed at Massachusetts Institute of Technology and used widely in the United States. Unlike other authentication schemes, Kerberos does not use public key technology. Instead, it uses symmetric ciphers and secrets shared between the Kerberos server and each individual user. Each user has a unique password, and the Kerberos server uses this password to encrypt messages sent to that user, so the message can't be read by anyone else.

key

A secret code, most often expressed as a numeric value, used to encrypt a message, to make the text unreadable to anyone but the intended recipient. If a message encrypted by a key must be decrypted by using the same key, the key is called a symmetric key. If a message encrypted by a key must be decrypted using a different key, the keys are called asymmetric keys, or a key pair. Key pairs (usually comprised of a public key and a private key) form the basis of public key cryptography.

key exchange

A scheme for two or more nodes to transfer a secret session key across an unsecured channel, such as the Internet.

key fingerprint

A uniquely identifying string of numbers and characters used to authenticate public keys.

key ID

A code that uniquely identifies a key pair. Two key pairs can have the same user ID, but they have different key IDs.
See also key and key fingerprint.

key length

The number of bits representing the key size; the longer the key, the stronger it is.

key management

The process and procedure for safely storing and distributing accurate cryptographic keys; the overall process of generating and distributing cryptographic keys to authorized recipients in a secure manner.

key pair

Public key cryptography uses a pair of key codes related to each other in this way: if you lock-up data using one key code, you can only unlock it using the other key code. And vice versa. One of the keys is made known publicly, while the other is kept private. The two, together, form a key pair.
See also key and keyring.

keyring

A set of digital codes, or keys, used to encrypt and decrypt messages in asymmetric cryptography. Each user has two types of keyrings: a private keyring and a public one. People who wish to receive encrypted messages typically publish their public keys in directories or make their keys otherwise available. To send them an encrypted message, all you have to do is get a copy of their public key, use the public key to encrypt your message, and send it to them. The only person who can decrypt the message is the person who possesses the matching private key.

key splitting

The process of dividing a private key into multiple pieces and sharing those pieces among several users. A designated number of users must bring their shares of the key together to use the key.