PGP signing

Allan Irving allanirving at
Mon Jun 9 14:38:53 UTC 2014

I see. That helps clear things up. Out of interest, can one edit the
comment left by a mail program on a signature and or the format? I'd
personally prefer to have the message signed after my message, so it would
say start there, rather with my message inbetween. Looks a bit...untidy.
However, if it's the only way, then so be it.

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On 9 June 2014 15:35, Adam Sampson <ats at> wrote:

> Allan Irving <allanirving at> writes:
> > What I see at the moment, when a message is just signed, is a wrapper
> > consisting of the encryption type the public key uses and then the key
> > itself towards the bottom. How does GPG prevent someone from copying
> this,
> > spoofing an email address and then signing a message?
> The signature data at the bottom isn't your public key. It's [*] a hash
> of the message, encrypted with your private key. To verify the
> signature, the receiver decrypts the signature using your public key,
> and checks it matches the hash of the message they received.
> If someone copied the signature onto a different message, the hash of
> the new message wouldn't match the hash retrieved from the signature, so
> verification would fail.
> [*] This is simplified a bit, and there are other ways of doing digital
> signatures that have the same effect. See the GPG manual:
> --
> Adam Sampson <ats at>                         <>
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