PGP: sequencing messages

[Winfried Tilanus]

On Tue, 04 Apr 2000 23:52:21 +0000, John Drabik wrote:

>a system that would "sequence" ALL of my
>outbound messages, and place some innocuous-looking text into the
>message with an encrypted version of the sequence number.  It would
>require EVERY outbound message to have a unique ID.

<snip>

>The hope is that they wouldn't even notice the "tag", thinking
>it to be some part of the signature line, but not as obvious as "PGP
>key: xxxxxxx" or some such thing.

The easiest way to do this, is to encrypt the serial number / id with
PGP and attach that to the message. That can be done quite easy with a
little rexx-script. But this gives a big overhead: even if you chop of
the PGP header and footer, than a six digit ID results in 4 lines. If
you try to transform this in something more 'innocent' then probably
the overhead gets much bigger.

I don't know where you need it for, but you might consider playing open
card: include de ID in plain text ("ID: xxxxxx") and sign all of the
message with PGP. It will probably have some preventive effect.

The other possibility is to use another encryption / verification
system. The easiest way to do that is just coding the serial ID into
some asci art without any encryption or checksum, or with just only a
simple checksum calculation before coding it. This should not be too
difficult to program in rexx.
Best wishes,
Winfried

http://web.inter.NL.net/users/Winfried/