Encryption transforms a message using secret keys so that intruders will not be able to reverse the transformation if they do not have the keys. Public key encryption utilizes a pair of keys, one for encryption and a different one for decryption. Every participant owns his/her own pair of keys. One key is the private key that is used only by the owner to decrypt messages. The other key is called the public key and it is used only for encryption. The owner sends out this public key to anyone who wants to encrypt a message for the owner.