Re: Encrypting outgoing message but not Gcc?

[spamtrap@koldfront.dk (Adam Sjøgren)]

On Sat, 06 Dec 2003 13:35:21 -0500, Lloyd wrote:

>> My archived copies are encrypted with the recipients as well as my
>> own public-key, so I can read them myself.

>> I don't think I've done anything special to make Gnus do that.

> Hmm ... as I mentioned in my other message a few minutes ago, I seem
> to need the _recipient's_ passphrase in order to decrypt my archived
> copies, even with the latest CVS of Gnus.

Ah, now I remember - sorry, I've been misinforming about the "done
anything special part"; actually I've put:

 encrypt-to asjo@koldfront.dk

in my ~/.gnupg/options.

> Also, I think there's a gap somewhere in my understanding of all
> this.  How can it be that something encrypted twice, once with the
> recipient's public key and once with yours, would only need your
> private key to be decrypted?  Wouldn't there have to be two
> decryptions, one for each of the previous encryptions?  Or in this
> case, is the encryption done with some sort of mathematical
> combination of both public keys, such that either corresponding
> private key can decrypt it?

I'm not able to adequately and comprehensibly explain the theory, but
I think it's a proporty of either assymetric key cryptography in
general or the way PGP/GnuPG is constructed (the latter being less
likely, probably, perhaps).

,----[ From man gpg ]
| --encrypt-to name
|           Same as --recipient but this one is intended for use in the
|           options file and may be used with your own user-id as an
|           "encrypt-to-self".  These keys are only used when there are
|           other recipients given either by use of --recipient or by
|           the asked user id.  No trust checking is performed for these
|           user ids and even disabled keys can be used.
`----


  Best regards,

-- 
 "Do not feed the oysters under the clouds"                   Adam Sjøgren
                                                         asjo@koldfront.dk