Asymmetric key cryptography, also known as public key cryptography, is a form of cryptography in which one key is used to encrypt a message and another is used to decrypt it, or one key is used to sign a message and another is used to verify it. The key used to decrypt or sign is kept private and cannot easily be derived from the public key, which is used to encrypt or verify. Asymmetric key ciphers include RSA, DSS, and ElGamal.