On Fri, 6 Dec 2002 09:22:40 +0100 Xavier Nodet <[EMAIL PROTECTED]> wrote:

> Actually, this 'auto-key-retrieve' option can be specified by the user
> in its gpg.conf (I guess... I will verify). So maybe we should not
> bother with that...

I verified that this option can be specified in the gpg.conf file.

So I guess we can forget it for now. In the future, it could be
interesting to provide some dialog asking for the user if he wants to
retrieve the missing key (with an option to remember the answer).

I had some other thoughts about PGP support. I will ask the
gnupg-users[1] list about them, but if you're interested, read on...

1. Encryption/signing layers can be artitrarily nested. For example,
   a message could be signed, encrypted, then signed again[2]. I'm not
   sure GPG handles all the levels on its own.

2. When a message is multiply signed as above, we should verify that the
   signatures have actually been done with the same key: the point in
   signing twice is to assert that the signer actually encrypted the
   document himself, thus proving that he wanted the recipient to get it
   (while, if a message is only signed then encrypted, the recipient
   could decrypt it, then forward it re-encrypted to a third person
   without this third person noticing that he was not the intended
   recipient).

3. When a message is signed, we should verify that the 'From:' header
   actually matches one of the IDs of the signing key. This prevents an
   attacker from forging headers to make the recipient believe he got
   the message from a third person. 

As you can see, a complete crypto handling may be more complicated than
just calling gpg with a few options... :( 

But I feel this is worthwhile, because not doing that could leave users
with a false security feeling.

[1] <http://lists.gnupg.org/mailman/listinfo/gnupg-users>
[2] See <http://world.std.com/~dtd/sign_encrypt/sign_encrypt7.ps> for
    reasons to do that. 

-- 
Xavier Nodet
"They that can give up essential liberty to obtain a little temporary
safety deserve neither liberty nor safety." - Benjamin Franklin, 1759.





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