A cryptographic key is data that is used to lock or unlock cryptographic functions such as encryption, authentication and authorization. Keys are typically designed to be both random and reasonably long such that they are difficult to guess. The following are common types of cryptographic key.
Asymmetric Key PairA matching public/private key pair whereby anyone can encrypt with the public key but only those who hold the private key can decrypt.
PublicThe public key in a asymmetric key pair.
PrivatePrivate keys may be part of a public/private asymmetric key pair. Alternatively, they can be used in symmetric encryption whereby you use the same key to encrypt and decrypt data. Private keys are generally kept secret.
Signature KeysKeys that are used to generate digital signatures for verifying identity, determining the integrity of data and non-repudiation.
Authentication KeysKeys that are used to verify identity, communications and data.
Wrapping KeysKeys that are used to encrypt other keys. For example, it is common to use public/private asymmetric keys for an initial exchange of symmetric private keys. This is done because symmetric encryption is generally faster than public key encryption.
Transport KeyBasically another term for a wrapping key. Transport keys are used to encrypt transport messages that contain other keys.
Key Agreement KeyAnother term for keys that are used to exchange other keys.
Ephemeral KeyA temporary key that is typically used to establish other keys.
Transient KeyAn asymmetric public/private key pair that is only used once. This may be done in order to implement functionality such as the ability to irrefutably identify the time that a digital signature was created.
Master KeyA key that is used to generate other keys using a key derivation function.
Authorization KeysAuthorization keys are used to provide a privilege. In many cases, these are used to prove that a message has been successfully decrypted. If you encrypt an authorization key with a public key you know that a client is in possession of the corresponding private key because they are able to send the authorization key back to you.
This is the complete list of articles we have written about encryption.
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