A man in Bonn has cracked a message encrypted with
wartime Germany's most-secure
Lorenzequipment within hours of its release
on 15 November, beating a rebuiltColossus
machinewithin Britain'sBletchley
Parkcode-breaking centre -which was delayed
in its task by solar activity disrupting radio
signals.
It sounds like several twists in the plot of a Second World War
thriller, but Joachim Schüth, who wrote special software to meet
the challenge, will be invited to visit Bletchley to receive a
prize from the nascent National
Museum of Computing.
"We really want to congratulate him," said Andy Clark, a
director and trustee of the museum. Schüth has cracked the hardest
of three signals transmitted yesterday by radio enthusiasts in
Germany from 11am, although Bletchley Park only managed to receive
them at 5.40pm.
Bletchley Park, the first base of the UK's signal interception
and decryption unit the Government Communications Headquarters
(GCHQ), is best-known for cracking Nazi Germany's widely-used
secure communications equipment, the
Enigma
machine. This allowed Britain to read much of its wartime
enemy's encrypted traffic, and Bletchley is credited with
shortening the Second World War by months or even years.
The Enigma traffic was broken by mechanical computers known as
bombes, and has
been commemorated by books including Robert Harris' novel Enigma,
which was made into a film. But the Colossus, which broke the
top-secret Nazi Lorenz traffic, is less famous. Clark said this is
partly because Britain told its wartime allies, including the
Soviet Union, about breaking Enigma, but not about breaking Lorenz,
and Colossus machines stayed in service after the end of the Second
World War. The Enigma-breaking story was first told in Poland in
1967, while that of Colossus only emerged during the 1970s.
It is likely to become rather better known, as a rebuilt
Colossus machine started work on the Lorenz-encoded message just
before 9am on 16 November. Tony Sale, a computer expert and former
employee of the UK security service MI5, started campaigning for
Bletchley Park to be saved from demolition in 1991. He spoke to
Infosecurity while supervising the operation of a fully-working
Colossus machine able to tackle Lorenz - which is now a listed
object in a listed building, representing the success of his
campaign.
Sale said it has been possible to rebuild a Colossus as the
design used standard components used in Post Office telephone
exchanges: Tommy Flowers, who worked alongside Alan Turing in
designing the Colossus, worked for the Post Office before and after
the war.
Due to British Telecom's programme of replacing these mechanical
exchanges over recent decades, plenty of these components were
available second-hand. A few components, such as the "bedstead"
through which the loop of paper holding the encoded message runs,
were made from scratch.
But the machine also includes nine original components, Sale
added: eight photo-cells and a mains transformer. "When the
engineers were dismantling Colossi at the end of the war,
photo-cells were a very nice thing to put in your pocket," he said,
as these are two inches high and 1.5 inches in diameter. However,
the rebuilt machine normally uses modern silicon photo diodes, as
the older photo-cells are fragile and need resting after prolonged
use. The mains transformer was also retained by an engineer, as
were some designs for the equipment, although original designs were
burnt in 1960.
The Colossus machine does not break Lorenz messages, but
attempts to find the wheel-settings - mechanical encryption keys -
used by the Germans (in this case, volunteers from
Heinz Nixdorf Museum Forum in
Paderborn). It does so by repeatedly running the paper loop into
which the message is punched through the machine, trying different
positions of a pair of Lorenz machine wheels one after another in a
brute-force attack.
Sale said the operator has to mark the start and end positions
of the message on the tape, then the Colossus reports likely
matches, using a scoring process. "Colossus does not 'know' when it
has a good thing," said Sale, only when a match looks more likely.
The operator then has to use the possible wheel positions to
attempt to decode the message using a Tunny machine - the British
named German war-time codes after fish. "If you have got it right,
out comes German," said Sale.
Andy Clark said that although the Colossus processes 5000
characters a second (5 kilohertz), and employs extensive parallel
processing, he assumes that the fastest machines doing this kind of
code-breaking are capable of working in Terahertz, processing
trillions of characters a second.
GCHQ, which moved to Cheltenham in 1952,
also invented
public-key encryption in 1973 - although it did not make the
work of its employee James Ellis public, leaving others to make the
same discovery independently.
Its press office said that GCHQ had no involvement in the work
beyond loaning equipment including a Lorenz machine to the museum.
"We applaud and support the ingenuity in rebuilding Colossus - a
fantastic piece of work," said a spokesperson.
This article first appeared on the
website of
Infosecurity magazine.