[SKRIVA] Review: Svenska kryptobedrifter/B Beckman
- From: "ahrvid@xxxxxxxxxxxx" <ahrvid@xxxxxxxxxxxx>
- To: <skriva@xxxxxxxxxxxxx>, <trufen@xxxxxxxxxxxxxxx>, <sverifandom@xxxxxxxxxxxxxxxxxxxx>
- Date: Mon, 1 Sep 2008 17:23:59 +0200 (CEST)
I think I have earlier touched the subject of cryptology and deciphering. A
well-known example is how the British in Bletchley Park, with important ground-
work being done previously by the Poles, mangaged to break into most of the
German Enigma ciphers during World War II. In this they had the help of early
number-crunching machines such as the "Bombes" and particulary the Colossus,
the first electronic computer in the world, constructed by among others the
famous Alan Turing.
It may be less well-known, but the fact is that the Swedish intelligence
service during WWII had their own successes with German ciphers. With the
fundamentals worked out by the brilliant professor in mathematics, Arne
Beurling (1905-1986), they broke into the German Geheimschreiber, a machine
used for teletype traffic and by many considered even more complex than the
Enigma.
Bengt Backman's book Svenska kryptobedrifter (Bonniers, 1996) tells all
about it. The title means "Swedish Crypto Achievements", and the book has also
been published under that in English (so you may be able to find it).
The Enigma was a machine the Germans used for wireless traffic (in fact
there were several Enigma designs, with eg a different number of enciphering
rotors; so there were numerous different Enigma ciphers) issued to all the
German WWII armed services in huge numbers (one source says 200 000 Enigmas
were produced). The Geheimschreiber ("Secret Writer") or G-schreiber was a
machine used for wire traffic.
They were not similar in design; the Enigma used revolving rotors to garble
the text. The G-schreiber on the other hand used a complicated set of relays;
the Enigma was intended for morse code and produced ordinary letters in the
form of lamps lighting up on a panel; the G-schriber used binary teletype code.
The G-schriber was probably the most complicated of the two, being the size of
desk, weighing hundreds of kilos; the Enigma was like a medium-sized protable
typewriter. The G-schreiber was also considered to be safer and was issued in
far less numbers.
The Swedes had a history in cryptology. One of the first cipher machines in
the world was constructed by the baron Gripenstierna and presented in a letter
to king Gustaf III in 1786 (consisting of a large drum with movable rings of
letters). Around the time of WWI a Swedish engineer, A Damm, began designing a
cipher machines, later in the early 20's perfected with the help of B Hagelin
and soon to be available on the commercial market as the Hagelin machine.
The Hagelin was in fact more or less the blueprint for machines like the
Enigma and was in different variations used in WWII by both the British,
Americans, Swedish, Italians, Japanese and many other militaries. (With
internal modifications of the wiring and such, though the principles of
operation were the same.)
In the 1930s the Swedish military became very interested in cryptology and
opened cipher-schools. One who took part in this was the young, then national
serviceman, Arne Beurling, who was able to prove that the then used Swedish
Army cipher machine had built in weaknesses. At the same time the Swedish
intelligence had some success with eg breaking into the Soviet navy ciphers.
The activities were intensified as WWII came closer and eventually broke
out, a war the Sweden stayed out of as being neutral - and was hoping to
continue to stay out of!
For this policy, the deciphering by the intelligence service became
absolutely crucial.
As Germany invaded Denmark and Norway, April 9th 1940, Sweden became
surrounded (Finland to the east had an uncertain peace with the Soviets, for a
short time) and her military forces were far from adequate to deter an
aggressor. The Germans who soon after also took most of Western Europe were at
the height of their might and could bully the Swedish government to some
concessions, including continued delivery of the valuable iron ore, transit by
train of soldiers on leave, and the right to use Swedish telegraph lines. The
last thing proved to be a lucky thing - for the Swedes. Of course the Swedish
intelligemce service tapped the lines, despite that the texts to begin with
looked like gibberish.
Beurling who had done his military service in the cipher school had
meanwhile become professor of mathematics at Uppsala Unversity. He called the
military himself, and suggested that he should be drafted - into the cipher
department. He was.
The Defence Staff crypto department was originally housed in a building in
central Stockholm, on Karlaplan No 4, which soon became known as "Karlbo". It
was originally one big, ordinary flat (which said "Jacobsson" on the door), but
as the activities grew the department annexed more and more of the surrounding
flats. It would eventually grow to a department of 500 or even more, which
would later move out of central Stockholm.
Security was very strict. None were allowed to talk about their work, only
say they did administrative work for the Defence Staff. (But this security
wasn't airtight, as we shall see later.) Decrypted messages were distributed on
a very limited scale, and had to be burned after being read.
What Beurling did, was practically the same as Turing & Co did in Bletchely
Park, about the same time, but with a different cipher machine.
But Beurling didn't have "Bombes" and early electronic number-crunchers to
help him. He simply ordered to get the print-outs of all G-schreiber traffic
for a certain day (May 25th 1940), and then looked himself into a room, with
paper and pencils, for a fortnight. And then he emerged and said "Iv'e got
it!".
No one is really sure *how* Beurling did it, but this book has an attempt to
reconstruct his reasoning. He never left more than tiny clues to how he worked,
and explained "A magician never reveals his tricks!". What we do know is that
he could break in with the help of lapses in the crypto discipline, that
overworked or even right out sloppy operators allowed themselves. (It was the
same with the Enigma. Lapses in routines were always the cracks that let the
Bletchley people in.)
Before I continue with Beurling, the Swedes had several other very talented
crypto analysts too. The Russian navy ciphers have been mentioned. One Yles
Gyldén broke into the French diplomatic ciphers. Several other ciphers were
also successfully attacked, but AFAIK not anything Enigma based. It seems the
Swedes never gave priority to Enigma; they had the land lines to tap and Enigma
was for the wireless.
The Swedish talent for SIGINT (SIGnal INTelligence) have lead to many cases
of intelligence cooperation with the "West", something that has continued until
today. In the 1950s a Swedish SIGINT DC3 was shot down by the Soviets over the
Baltic Sea, filled with American listening equipment (the info the Swedish
military got was obviously going to be shared with the Americans; however the
DC3 mission was "legal" and over international waters!).
From June 1940 until May 1943, the Swedes could read all or substantial
parts of the German military cable traffic that went through Sweden, ie traffic
to and from Finland and Norway. It was 10 000's of telegrams, and many would
contain general assessments of the military situation and dispositions in the
whole European theatre. So the Swedish military intelligence got a front row
seat to the German military capacity. They would know when a threat was real or
when it was just a diplomatic bluff, and of course so would the government
which could issue orders of partial mobilisations, movement of troops, etc to
adapt.
On several occasions, there were partial mobilisations to counter possible
German threats (the "midsummer crisis" of 1941 around the time of operation
Barbarossa, an invasion threat of February 1942, and of course August 1943 when
the Swedes cancelled the German use of Swedish railways).
The Defence Staff crypto department may not be the sole reason for Sweden
being able to stay out of the war, but it certainly did a very substantial
contribution towards it!
Despite top secrecy, a spy crept into the crypto department. A courier by the
name Allan Emanuel Nyblom who transported the deciphered documents from the
crypto department to the Defence Staff was in January 1942 revealed as a spy
for - the Soviets. He did it partly for ideological reasons, partly for money,
and was only revealed after he had been involved in an affair of illegal
abortions (in which a failed abortion lead to a woman's death).
This didn't hurt the Swedes capacity to read German telegrams (but the
Russians tightened their own cipher security) since they had no reason to tip
the Germans off - they were at war with Germany. However, another leak
jeopardised the crypto department. Exact details has never been found out, but
the leak probably came from the Finns - who were at war on the German side. The
Finns learned that the Swedes seemed to know a lot about the Germans, and
hinted that to them.
This happened in mid-1942 and one possible leak is the Finnish military
attache in Stockholm, one colonel Stewens, who often moved around in the
Defence Staff HQ. He may even have seen decrypted German messages.
But even after this, it would up to a year for the Germans to tighten up
their security. They were slow in changing their routines, introduce new
ciphers, and new cipher machines. They did in fact begin using a new modified G-
schreiber, but it was easy to break into for the Swedes; a further new model
was also broken into. Only a fourth, unknown cipher machine proved too much for
the Swedes. At this time, it didn't matter too much, though. This was after El
Alamein and Stalingrad, the German war machine had lost its edge. The threat
against Sweden was substantially smaller. The crypto department had gotten us
through the worst, when the info was crucial.
How did Arne Beurling do his successful cipher attack on the G-schreiber?
A "reconstruction" was done by one Car-Gösta Borelius, who himself worked
with the G-schreiber material. It is known that Beurling ordered material from
25th of May 1940, when the lines had been established and worked well but
before that operators had time to get used to them.
Here are some details.
One "code" the operators would use often was "QRV", international
telepgraphese for "Do you read me?". Another thing was that the lines often had
disturbances which for instance would lead the character table to "shift" to
numbers (numbers were reached after a certain "shift" character). To counter
this, the telegrams would often replace the character for "space" with the (non-
printable) characters for "shift to alphabetical" followed by an extra "space".
If the text was shifted to numbers, it would therefore automatically shift back
to letters at every space position.
The Swedes used their own "pseudo" coding for the silent (non-printable)
characters, in which "shift to alphabetical" + "space" would print as "35".
So Beurling would know that "QRV" would often come early in a message
exchange, and that "space" would usually written as "35" (to to make sure that
the tables didn't shift to numbers).
Also, between enciphered messages the operators, who were "on-line" to each
other", would produce quite a lot of chat which wasn't enciphered, to prepare
for the enciphered text to be sent. This would give clues to what kind of
messages one was to expect, eg: in clear "I begin to encipher now. Do you
read?", probable answer (enciphered) "Yes, I can read". Another weak point was
that when an operator had to resend a message, it was complicated to make a new
setting for the G-schreiber, byt realatively easy to go back to the previous
key. Operators would therefore often do this, which was a breach of standard
procedures and made it easier to break into the traffic.
Beurling discovered that the plain text of 3 and 5 had one pulse the same
and four different (they were written as a binary with five binary pulses),
this had also to be the case in the enciphered state. For a guessed 3 there
existed only five possible 5 and vice versa. It was therefore easy to establish
spaces between words. And a guessed 3 gave only five possible Q and V in QRV.
Then he saw that a change from one character in the plain text to a cipher
character after the "overlaying" (ie passing through the G-schreiber relays)
consisted of a change in polarity for some of the pulses in the plain text
character, and for all the characters in the column it was always the *same*
character that changed. This could be analysed manually on big "work sheets".
With clues like this, Beurling could begin to look for patterns that could
reveal the inner wiring and layout of the G-schreiber. From his instructions,
the telecom company L M Ericsson, designed functional equivalents to the G-
schreiber, which became known as "Appar" ("Apps", from "apparatus"). Every
morning the Swedish crypto department would go through the latest messages, and
find out the keys (usually from messages resent in the same wording in several
copies with different keys), which would then be handed over to the "Apps" and
be deciphered, more or less in real time.
It should be noted that the machines, both the G-schreiber and Enigma,
probably gave perfectly adequate security, in a mathematical sense. It was
sloppiness in procedures and with the operators that opened cracks that
decryption attempts could put to use.
It was an operation amazingly similar to Bletchley Park, which however was
much bigger (10 000's of people involved), possibly because the volume of
messages Bletchley handled was much bigger (and Britain was also in a shooting
war). Beurling did his thing alone, though, not together in a whole team, and
just with his brain - not with any number crunching machines.
The author and crypto historian David Kahn wrote: "Quite possibly the finest
feat of cryptanalysis performed during the Second World War was Arne Beurling's
solution to the Secrect of the Geheimschreiber."
Beurling would after the war be offered a position at Princeton, where he BTW
had the same office as Albert Einstein. He did not - according to this book -
became more than moderately successful, the reason being that he interested
himself in rather obscure fields of mathematics that didn't attract much
attention.
The Defence Staff's crypto department was in 1942 turned into The Defence
Radio Institution (or in Swedish Försvarets Radio-Anstalt, abbr FRA), which is
an organisation that lately has become the subject of a heated debate.
FRA has for a long time, probably not without success, been snapping up all
kinds of signals and traffic going through the ether. In later years, however,
much of the traffic that used to go through the air or via satellites, has move
to cables.
So the Swedish parliament in the beginning of the summer passed the
*highly*controversial so called FRA Act, with empowered the FRA to scan *all*
cable traffic going out of, into or across Sweden for "outer threats". (There
is little doubt that they hope to catch a lot of Russian traffic.) However,
this means they would also "scan" all innocent Internet traffic to and from
ordinary citizens. It is basically a Swedish version of Echelon (if you have
heard that name before). Quite often ordinary traffic from ordinary citizens
"bounces" through a foreign server, or goes across a border due to technical
reasons. One can never know when FRA will be listening.
People in general have been outraged by this FRA Act, which is seen by many
in the public debate as a threat to personal integrity. There has been lots of
protests and the government has (mosly in vain) tried to defend itself. The
debate has not died down. There have been street demonstrations. There are
articles about it in the papers every day. The so called "blogosphere" has
attacked the FRA Act in a massive manner. The question will be up in the
parliament again this fall.
And, strangely enough, it all started with breaking into German messages
during World War Two.
--Ahrvid
More information:
The Geheimschreiber Secret - Arne Beurling and the success of Swedish signals
intelligence:
http://frode.home.cern.ch/frode/ulfving/ulfving.html
About the Geheimschreiber:
http://july.fixedreference.org/en/20040724/wikipedia/Geheimfernschreiber
About Arne Beurling:
http://wapedia.mobi/en/Arne_Beurling
The Geheimschreiber Secret (a very good article!):
http://web.usna.navy.mil/~wdj/papers/cryptoday/ulfving_weierud_secret.pdf
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