A form of cryptography which uses two keys - a private key and a public key. Anything encrypted with your public key can only be decrypted with your private key. So you can distribute your public key to anyone in the world, because it only is useful for encrypting data intended for you. The private key, on the other hand, must be kept secured. This form of crypto is used frequently for encrypting e-mail because you don't need a secure mechanism for exchanging the public key. Even if someone intercepts it, without your private key they won't be able to decrypt any of the messages intended for you.
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.
Also known as asymmetric key cryptography. In public-key cryptosystems, everyone has two related complementary keys, a publicly revealed key and a secret key (also frequently called a private key). Each key unlocks the code that the other key makes. Knowing the public key does not help you deduce the corresponding secret key. The public key can be published and widely disseminated across a communications network. This protocol provides privacy without the need for the same kind of secure channels that a conventional cryptosystem requires.