An encryption technique developed to overcome the limitations of secret-key cryptography (see separate entry). Public key (also called “asymmetric key”) cryptography uses two mathematically related keys: A public key to encrypt messages, and a private key to decrypt them. In a public-key system, you communicate privately by encrypting your message using the public key of your intended recipient. Although everyone else knows the recipient’s public key, it is useless for decrypting a message encrypted with it. Only the corresponding private key, known only to the recipient, can decrypt the message.