(1) An encrypted message that uses both secret key and public key cryptography methods. A secret key is used to encrypt and decrypt the message, but the public key method is used to send the secret key to the other party. See
RSA.
(2) A frame, or packet, of data that has been encrypted for transmission over a network.
(3) A term occasionally used to describe inserting data into a packet or frame for transmission over a network. The envelope metaphor implies a container. See
encapsulation and
container.