Ethics Reader- cyberethics ch38

To be sure that the data are really sent by the sender of the electronic message, the double encryption of PGP is a suitable and widely used protocol. The sender encrypts his message with his secret key firstly and with the public key of the receiver secondly and afterwards he sends the message. The receiver must decrypt that message first with his own secret key and second with the public key of the sender according to the header. When the message is readable after this double decryption, one can be sure that the message was meant to be received by the decrypting receiver and the message was really sent by the sender named in the header of the message. Thus: double encryption needs the sender identification in order to decrypt the message with the senders public key.