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GnuPG's 10th birthday

From: Werner Koch
Subject: GnuPG's 10th birthday
Date: Thu, 20 Dec 2007 10:55:16 +0100
User-agent: Gnus/5.110007 (No Gnus v0.7)

               A Short History of the GNU Privacy Guard

It's been a decade now that the very first version of the GNU Privacy
Guard [0] has been released.  This very first version was not yet
known under the name of GnuPG but dubbed "g10" as a reference on the
German constitution article on freedom of telecommunication
(Grundgesetz Artikel 10) and as a pun on the G-10 law which allows the
secret services to bypass these constitutional guaranteed freedoms.

Version 0.0.0 released on December 20th 1997 [1], was a barely working
replacement of PGP avoiding all patented algorithm by using Elgamal
and Blowfish instead of RSA and IDEA.  It was prominently marked as a
test version but nevertheless included most of the features of the
current GnuPG.  The data format however was not compatible with
OpenPGP but oriented towards the PGP 2 format with a few extensions
(e.g. to allow streaming of data).  The OpenPGP working group was
founded back in fall 1997 and I learned a bit to late about it to
build "g10" according to the then existing draft.  For copyright
reasons it was practically not possible to reverse engineer the format
used by PGP-5, so the establishment of the OpenPGP WG was the right
thing at the right time.

Before talking about GnuPG we need to go some more years back in
history: To help political activists Phil Zimmermann published a
software called Pretty Good Privacy (PGP) in 1991.  PGP was designed
as an easy to use encryption tool with no backdoors and disclosed
source code.  PGP was indeed intended to be cryptographically strong
and not just pretty good; however it had a couple of inital bugs, most
of all a home designed cipher algorithm.  With the availability of the
source code a community of hackers (Branko Lankester, Colin Plumb,
Derek Atkins, Hal Finney, Peter Gutmann and others) helped him to fix
these flaws and a get a solid version 2 out.

Soon after that the trouble started.  As in many counties the use or
export of cryptographic devices and software was also strongly
restricted in the USA.  Only weak cryptography was generally allowed.
PGP was much stronger and due to the Usenet and the availability of
FTP servers and BBSs, PGP accidently leaked out of the country and
soon Phil was sued for unlicensed munitions export.  Those export
control laws were not quite up to the age of software with the funny
effect that exporting the software in printed form seemed not to be
restricted.  MIT Press thus published a book with the PGP source code
which was then scanned outside the USA to form the base of PGP-2i ("i"
for international).  Since then that version was used widely.

The criminal investigations against Phil ended in 1996 and he founded
PGP Inc to write PGP-5.  The first public release was done in spring
1997.  The same year at the 39th IETF meeting at Munich in August Phil
Zimmermann and Jon Callas asked the IETF to setup a working group to
publish a standard for the protocol used by PGP-5 under the name
OpenPGP.  The main drive behind this was to allow widespread use of
strong encryption even if at some point the new company would decide
to stop selling and supporting PGP.  As it turned out PGP Inc was
acquired by Network Associates just a few months later and in 2002
this company actually ceased support and development of PGP (though
the PGP product was later continued by the new PGP Corporation).

Also often claimed to be Free Software, PGP has never fulfilled the
requirements for it: PGP-5 is straight proprietary software; the
availability of the source code alonedoes not make it free.  PGP-2 has
certain restrictions on commercial use [2] and thus puts restrictions
on the software which makes it also non-free.  Another problem with
PGP-2 is that it requires the use of the patented RSA and IDEA
algorithms.  The patent on RSA was only valid in the USA but the
patent on IDEA was and is still valid [3] in most countries.

Although the GNU project listed a requirement for a PGP replacement
for some years on its task list, it was not possible to start
implementing it as long as patents on all public key algorithms were
valid.  That changed when in April 1997 the basic patent on public key
algorithms expired (the Diffie-Hellman US patent 4200770) and finally
in August when the broader Hellman-Merkle patent (4218582) expired.

A month later, at the Individual-Network Betriebstagung at Aachen [4],
Richard Stallman continued his talk with a BoF session where he asked
the European hackers to start implementing public key software.  The
arms trafficker laws of the USA prohibited the GNU project to write
such software in their country or even by US citizens working abroad.
Thus he told the European hackers that they are in the unique position
to help the GNU with crypto software.

Being tired of writing SMGL conversion software and without a current
fun project, I soon found my self hacking on PGP-2 parsing code based
on the description in RFC-1991 and the pgformat.txt file.  As this
turned out to be easy I continued and finally came up with code to
decrypt and create PGP-2 data.  After I told the GNU towers that I
will take up the PGP replacement implementation I spent the rest of
the year replacing IDEA by Blowfish, RSA by Elgamal, implementing
streaming encryption, adding some key management and getting the code
into a reasonable shape.

There used to be a plan for a free version of Secure Shell called PSST
(later known as LSH) with a somewhat populated mailing lists
maintained by Martin Hamilton.  Martin was the so kind to setup a
mailing list for g10 too and announced it on that list.  This way we
got the first subscribers.  Eventually I made the first tarball, put
it up to, the FTP server of the German Unix User Group,
and wrote an announcement [5].

Right the next day Peter Gutmann offered to allow the use of his
random number code for systems without a /dev/random.  This eventually
helped a lot to make GnuPG portable to many platforms.  The next two
months were filled with code updates and a lengthly discussion on the
name; we finally settled for Anand Kumria's suggestion of GnuPG and
made the first release under this name (gnupg-0.2.8) on Feb 24 [6].
Just a few days later an experimental version with support for Windows
was released.  (That release also fixed an alignment problem on Alpha
boxes which was detected due to kernel log files filling up the hard
disk and an admin asking whether they really need to be backed up. ;-)

In July 1998 the first more or less OpenPGP draft compliant version
was released.  Matthew Skala had contributed Twofish code done cleanly
From scratch (Twofish was at that time a promising AES candidate and
suggested by Schneier as a Blowfish replacement; however we had some
copyright concerns with the reference code).  Michael Roth contributed
a Triple-DES implementation later the year and thus completed the
required set of OpenPGP algorithms.  Over the next year the usual
problems were solved, features discussed, complaints noticed and
support for gpg in various other software was introduced by their
respective authors.

Finally, on September 7, 1999 the current code was released as version
1.0.0 with the major update of including Mike Ashley's GNU Privacy
Handbook [7].  A year later the RSA patent was to expire on September
20; the patent holder placed the patent into the public domain 3 weeks
earlier and thus we could release 1.0.3 with RSA support already on
September 18.  One of the major obstacles on widespread use public
cryptography had gone (far too late of course).

Also in 1999 the German government decided that strong encryption will
not be regulated in any way and that its use is recommended for
everyone.  To publicly support this statement the Ministry of
Economics funded the porting of GnuPG and related software to
Microsoft Windows [8].  The US government was not keen to see that and
tried to urge the German government to revise the decision to allow
unregulated distribution of crypto software [9].  That did not work
out and to the end the USA had no other way than to weaken their own
export rules.

Although we still develop GnuPG using servers located in Europe the
new US export controls eventually allowed US hackers to contribute to
GnuPG development.  In 2001 David Shaw joined the project and since
then he is one of the most active GnuPG hackers and the co-maintainer.

It's now a long time since GnuPG could be managed as a fun project and
thus I now spend most of my professional life maintaining and extending
GnuPG.  In 2001 I founded g10 Code, a Free Software company for the
development and support of GnuPG and related software.  The most known
project is probably GnuPG-2 which started under the name NewPG as part
of the broader Aegypten project.  The main goal of Aegypten was to
provide support for S/MIME under GNU/Linux and integrate that cleanly
with other mail clients, most notably KMail.  Although having been
actively used since 2004, we released 2.0.0 only one years ago.

It was not that much fun writing X.509/CMS (commonly named S/MIME)
software compared to the elegant and very interoperable OpenPGP
protocol.  Having mastered that we meanwhile achieved to provide a
software which is really useful and works nicely with almost any other
S/MIME implementation.  It also turned out that we could port GnuPG-2
to Windows - despite my original claim that a modern POSIX platform
will be needed for GnuPG-2.  This development also showed that it is
viable to develop Free Software as a business.

With the new tools and from a user's perspective S/MIME and OpenPGP
will soon not make much of a difference anymore.  However I had to
smile when I today read a report on the last RSA Europe conference
where a quick poll during a talk showed that OpenPGP is the mostly
used encryption protocol.

Recall that GnuPG is just one tool; there are numerous other tools out
to solve related privacy problems.  Kudos to all who worked on writing
and deploying privacy tools over all these years!

Happy Hacking,


[0] http://www/
[2] from pgpdoc2.txt: "Finally, if you want to turn PGP into a
    commercial product and make money selling it, then we must agree
    on a way for me to also make money on it. [...] Under no
    circumstances may PGP be distributed without the PGP
    documentation, including this PGP User's Guide."
[3] "valid" is meant in the sense the patent holders use it and does
    not imply that I regard patents on software a valid concept.  See .
    There are just a few mails in December mainly discussing patent things.

Die Gedanken sind frei.  Auschnahme regelt ein Bundeschgesetz.

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