pgp

Doug Stewart doug.dastew at gmail.com
Tue Aug 11 01:31:30 UTC 2009


On Mon, Aug 10, 2009 at 9:16 PM, Joel Goguen <jgoguen at jgoguen.ca> wrote:

> On 10 August 2009 21:27:40 Doug Stewart wrote:
> > I have a file with a public key block , and a message that is incrypted
> by
> > the same person.
> >
> > How do I use the key to see the message.
> > What software?
> >
> > Ubuntu 9.04
> >
> > I know a little about
> > seahorse  and pgpgpg
> >
> > Doug
> The way public key crypto works is slightly different for signing and
> encrypting.  In both cases you have a public key (publicly accessible by
> anyone) and a private key (kept secret, only the sender may have this).
>  For
> the sake of simplicity, let's call the sender "Alice" and the receiver
> "Bob".
> They both have their own private and public keys.
>
> For signing, Alice will sign the message using her private key.  Anyone on
> the
> Internet may use her public key to verify the signature and see that it was
> Alice's private key used to sign the message.
>
> Encrypting is basically the opposite.  If Alice wants to send Bob an
> encrypted
> message, she would encrypt the message using Bob's public key.  At this
> point,
> no one but Bob can decrypt the message.  When Bob receives the message, he
> will use his private key to decrypt the message.
>
> So, if you have an encrypted message, it must be encrypted with your public
> key, and you would use your private key to decrypt it.  Most mail clients
> (KMail, Evolution, Thunderbird with Enigmail) can do this automatically,
> but
> if not you can save the encrypted block (including the lines before and
> after
> starting with dashes) to a file (~/gpg-message.txt) and decrypt with this
> command:
>
> gpg -d ~/gpg-message.txt
>
> This will print the message out on the terminal.  If you don't have a
> private
> key, or if the message was encrypted using someone else's public key, you
> won't be able to read it.
>
> It's also possible you have a signature - they look similar to encrypted
> messages, except signed messages have a small block of gibberish after a
> plaintext message.  This message right here is signed, so you can look at
> it
> and see what a signed message looks like.  To verify a signature, simply
> copy
> the message to one file (~/plain-message.txt) and the signature to another
> file
> (~/gpg-sig.txt) and use this command:
>
> gpg --verify ~/gpg-sig.txt ~/plain-message.txt
>
> It would of course be preferred to use a mail client that can do this
> automatically, to avoid the chances of errors copying and pasting the
> messages/signatures.
>
> Hope that helps!
>
> --
> Joel Goguen
> Ubuntu User #15951
> When we help, we benefit
>
> --
> ubuntu-ca mailing list
> ubuntu-ca at lists.ubuntu.com
> https://lists.ubuntu.com/mailman/listinfo/ubuntu-ca
>
> Thanks Joel   - our emails crossed id cyber space.

That is very helpful , I am still wondering about a GUI
Doug
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