A key is a piece of information used by acipher forencryption and/ordecryption.

Encrypted messages should remain secure even if everything about the cryptosystem, except for the key, is public knowledge.

Insymmetric-key cryptography, the same key is used for both encryption and decryption.This key is referred to as theshared key, or thesecret key.

Inpublic-key cryptography, there exists a pair of related keys known as thepublic key andprivate key. The public key is freely available, whereas the private key is kept secret. The public key is able to encrypt messages that only the corresponding private key is able to decrypt, and vice versa.

See also

• Kerckhoffs's principle on Wikipedia
• Related glossary terms:
  • Block cipher mode of operation
  • Cipher
  • Ciphertext
  • Cipher suite
  • Cryptanalysis
  • Cryptography
  • Decryption
  • Encryption
  • Plaintext
  • Public-key cryptography
  • Symmetric-key cryptography