A publicly available implementation of a public-key encryption system using no trusted third party. Note: PGP can be used to apply a digital signature to a message without actually encrypting the text of the message. This is normally used in public postings where the user wants all readers to be able to see the message text and also wants the reader to be able to confirm that the message is unaltered from its original form. Once a digital signature is created with PGP, it is impossible for anyone to modify either the message or the signature without the modification being detected by PGP.