An asymmetric cipher that uses two keys, one for encryption, the public key, and the other for decryption, the private key. As implied by the key names, the public key used to encode plaintext can be made available to anyone. However, the private key must remain secret. Only the private key can decrypt the ciphertext. The public key algorithm used in this process is slow (on the order of 1,000 times slower than symmetric algorithms), and is typically used to encrypt session keys or digitally sign a message.