Non-Repudiation of Origin

Because of the way digests (MD5 hashes), signatures, and messages are abstracted in PGP, it allows people to forward authenticated messages that can then be verified by the new recipient. For example:

• Tom signs a message and forwards it to Jane.
• Jane signs the message and forwards it to Harry.
• Harry can verify that Jane sent the message to him.
  pgp message.pgp
  
• Harry can verify that Tom originally signed the message.
  pgp message
  

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