Ian,
usage of MIME RFC 1847 (multipart/signed) could probably fit your needs for
human readable clear signed documents, that fit in a single file.
Contrary to what people have been saying, MIME messages can be stored in a
single file - in fact thats a natural storage medium for them. One of
MIME's purposes was to flatten out multipart messages (text & attachments)
so they can be streamed over a connection. The MIME stream (or file)
contains formatting information which makes it easy to break out the
original components.
Included below is a example of a clear text signed message:
Example message:
From: Michael Elkins <elkins(_at_)aero(_dot_)org>
To: Michael Elkins <elkins(_at_)aero(_dot_)org>
Mime-Version: 1.0
Content-Type: multipart/signed; boundary=bar; micalg=pgp-md5;
protocol="application/pgp-signature"
--bar
Content-Type: text/plain; charset=iso-8859-1
Content-Transfer-Encoding: quoted-printable
=A1Hola!
Did you know that talking to yourself is a sign of senility?
It's generally a good idea to encode lines that begin with
From=20because some mail transport agents will insert a greater-
than (>) sign, thus invalidating the signature.
Also, in some cases it might be desirable to encode any =20
trailing whitespace that occurs on lines in order to ensure =20
that the message signature is not invalidated when passing =20
a gateway that modifies such whitespace (like BITNET). =20
me
--bar
Content-Type: application/pgp-signature
-----BEGIN PGP MESSAGE-----
Version: 2.6.2
iQCVAwUBMJrRF2N9oWBghPDJAQE9UQQAtl7LuRVndBjrk4EqYBIb3h5QXIX/LC//
jJV5bNvkZIGPIcEmI5iFd9boEgvpirHtIREEqLQRkYNoBActFBZmh9GC3C041WGq
uMbrbxc+nIs1TIKlA08rVi9ig/2Yh7LFrK5Ein57U/W72vgSxLhe/zhdfolT9Brn
HOxEa44b+EI=
=ndaj
-----END PGP MESSAGE-----
--bar--
In this example the text is quoted printable encoded, but it could be left
unencoded. QP is recommended for 7 bit transport over the internet though.
However this is not an issue if you are storing locally.
I'm no expert on cryptography, but I do have considerable experience in
implementing MIME. Feel free to grill me on the subject.
Cheers - Linz
--
Lindsay Mathieson
Black Paw Communications
Using MailCat for Win32 Beta Vs 2.6.1.2, on November 28, 1997, in Win95
4.0
http://www.blackpaw.com/