Siemens and Halske T52
Encyclopedia
Siemens AG
Siemens AG is a German multinational conglomerate company headquartered in Munich, Germany. It is the largest Europe-based electronics and electrical engineering company....
and Halske T52, also known as the Geheimfernschreiber ("secret teleprinter"), or Schlüsselfernschreibmaschine (SFM), was a World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
German
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
teleprinter
Teleprinter
A teleprinter is a electromechanical typewriter that can be used to communicate typed messages from point to point and point to multipoint over a variety of communication channels that range from a simple electrical connection, such as a pair of wires, to the use of radio and microwave as the...
cipher
Cipher
In cryptography, a cipher is an algorithm for performing encryption or decryption — a series of well-defined steps that can be followed as a procedure. An alternative, less common term is encipherment. In non-technical usage, a “cipher” is the same thing as a “code”; however, the concepts...
machine. The machine and its traffic were codenamed Sturgeon by British
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
cryptanalysts.
While the Enigma machine
Enigma machine
An Enigma machine is any of a family of related electro-mechanical rotor cipher machines used for the encryption and decryption of secret messages. Enigma was invented by German engineer Arthur Scherbius at the end of World War I...
was generally used by field units, the T52 was an online
ONLINE
ONLINE is a magazine for information systems first published in 1977. The publisher Online, Inc. was founded the year before. In May 2002, Information Today, Inc. acquired the assets of Online Inc....
machine used by Luftwaffe
Luftwaffe
Luftwaffe is a generic German term for an air force. It is also the official name for two of the four historic German air forces, the Wehrmacht air arm founded in 1935 and disbanded in 1946; and the current Bundeswehr air arm founded in 1956....
and German Navy units, which could support the heavy machine, teletypewriter and attendant fixed circuits
Electrical network
An electrical network is an interconnection of electrical elements such as resistors, inductors, capacitors, transmission lines, voltage sources, current sources and switches. An electrical circuit is a special type of network, one that has a closed loop giving a return path for the current...
. It fulfilled a similar role to the Lorenz SZ40 and SZ42
Lorenz cipher
The Lorenz SZ40, SZ42A and SZ42B were German rotor cipher machines used by the German Army during World War II. They were developed by C. Lorenz AG in Berlin. They implemented a Vernam stream cipher...
machines in the German Army.
The British cryptanalysts of Bletchley Park
Bletchley Park
Bletchley Park is an estate located in the town of Bletchley, in Buckinghamshire, England, which currently houses the National Museum of Computing...
codenamed the German teleprinter ciphers Fish
Fish (cryptography)
Fish was the Allied codename for any of several German teleprinter stream ciphers used during World War II. Enciphered teleprinter traffic was used between German High Command and Army Group commanders in the field, so its intelligence value was of the highest strategic value to the Allies...
, with individual cipher-systems being given further codenames: just as the T52 was called Sturgeon, the Lorenz machine was codenamed Tunny.
Operation
The teleprinters of the day emitted each character as five parallel bitBit
A bit is the basic unit of information in computing and telecommunications; it is the amount of information stored by a digital device or other physical system that exists in one of two possible distinct states...
s on five lines, typically encoded in the Baudot code
Baudot code
The Baudot code, invented by Émile Baudot, is a character set predating EBCDIC and ASCII. It was the predecessor to the International Telegraph Alphabet No 2 , the teleprinter code in use until the advent of ASCII. Each character in the alphabet is represented by a series of bits, sent over a...
or something similar. The T52 had ten pinwheel
Pinwheel (cryptography)
In cryptography, a pinwheel was a device for producing a short pseudorandom sequence of bits , as a component in a cipher machine. A pinwheel consisted of a rotating wheel with a certain number of positions on its periphery. Each position had a "pin" or "lug" which could be either "set" or "unset"...
s, which were stepped in a complex nonlinear way, based in later models on their positions from various delays in the past, but in such a way that they could never stall. Each of the five plaintext
Plaintext
In cryptography, plaintext is information a sender wishes to transmit to a receiver. Cleartext is often used as a synonym. Before the computer era, plaintext most commonly meant message text in the language of the communicating parties....
bits was then XORed with the XOR sum of 3 taps from the pinwheels, and then cyclically adjacent pairs of plaintext bits were swapped or not, according to XOR sums of three (different) output bit
Bit
A bit is the basic unit of information in computing and telecommunications; it is the amount of information stored by a digital device or other physical system that exists in one of two possible distinct states...
s. The numbers of pins on all the wheels were coprime
Coprime
In number theory, a branch of mathematics, two integers a and b are said to be coprime or relatively prime if the only positive integer that evenly divides both of them is 1. This is the same thing as their greatest common divisor being 1...
, and the triplets of bits that controlled each XOR or swap were selectable through a plugboard.
This produced a much more complex cipher than the Lorenz machine, and also means that the T52 is not just a pseudorandom number generator
Pseudorandom number generator
A pseudorandom number generator , also known as a deterministic random bit generator , is an algorithm for generating a sequence of numbers that approximates the properties of random numbers...
-and-XOR cipher. For example, if a cipher clerk erred and sent two different messages using exactly the same settings — a depth of two in Bletchley jargon — this could be detected statistically but was not immediately and trivially solvable as it would be with the Lorenz.
Models
In addition, a number of conceptual flaws (including very subtle ones) had been eliminated. One such flaw was the ability to reset the keystream
Keystream
In cryptography, a keystream is a stream of random or pseudorandom characters that are combined with a plaintext message to produce an encrypted message ....
to a fixed point, which led to key reuse by undisciplined machine operators.
Cryptanalysis
Following the occupation of DenmarkDenmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...
and Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
the Germans started to use a teleprinter circuit which ran through Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....
. The Swedes immediately tapped the line, in May 1940, and the mathematician
Mathematician
A mathematician is a person whose primary area of study is the field of mathematics. Mathematicians are concerned with quantity, structure, space, and change....
and cryptographer Arne Beurling
Arne Beurling
Arne Carl-August Beurling was a Swedish mathematician and professor of mathematics at Uppsala University and later at the Institute for Advanced Study in Princeton, New Jersey....
cracked the two earliest models in two weeks, using just pen and paper. The telephone company Ericsson
Ericsson
Ericsson , one of Sweden's largest companies, is a provider of telecommunication and data communication systems, and related services, covering a range of technologies, including especially mobile networks...
manufactured a number of T52 analogue machines, that could decode the messages once the key settings had been found by hand. The Swedes then read traffic in the system for three years, not only between Berlin and Oslo, but also between Germany and the German forces in Finland, and of course the German embassy in Stockholm
Stockholm
Stockholm is the capital and the largest city of Sweden and constitutes the most populated urban area in Scandinavia. Stockholm is the most populous city in Sweden, with a population of 851,155 in the municipality , 1.37 million in the urban area , and around 2.1 million in the metropolitan area...
. In total, the Swedes intercepted 500,000 German messages and decrypted 350,000. However, poor security meant the Germans eventually became aware of this. An improvement in T52 security in 1942 was defeated by the Swedes. However, a second upgrade in mid-1943 was not and the flow of decrypted messages came to an end.
The British at Bletchley Park later also broke into Sturgeon, although they did not break it as regularly as they broke Enigma or Tunny. This was partly because the T52 was by far the most complex cipher of the three, but also because the Luftwaffe very often retransmitted Sturgeon messages using easier-to-attack (or already broken) ciphers; thus, attacking Sturgeon was not the most economical way to get the plaintext.
The British first detected T52 traffic in summer and autumn of 1942. One link was between Sicily
Sicily
Sicily is a region of Italy, and is the largest island in the Mediterranean Sea. Along with the surrounding minor islands, it constitutes an autonomous region of Italy, the Regione Autonoma Siciliana Sicily has a rich and unique culture, especially with regard to the arts, music, literature,...
and Libya
Libya
Libya is an African country in the Maghreb region of North Africa bordered by the Mediterranean Sea to the north, Egypt to the east, Sudan to the southeast, Chad and Niger to the south, and Algeria and Tunisia to the west....
, codenamed "Sturgeon
Sturgeon
Sturgeon is the common name used for some 26 species of fish in the family Acipenseridae, including the genera Acipenser, Huso, Scaphirhynchus and Pseudoscaphirhynchus. The term includes over 20 species commonly referred to as sturgeon and several closely related species that have distinct common...
", and another from the Aegean
Aegean Sea
The Aegean Sea[p] is an elongated embayment of the Mediterranean Sea located between the southern Balkan and Anatolian peninsulas, i.e., between the mainlands of Greece and Turkey. In the north, it is connected to the Marmara Sea and Black Sea by the Dardanelles and Bosporus...
to Sicily
Sicily
Sicily is a region of Italy, and is the largest island in the Mediterranean Sea. Along with the surrounding minor islands, it constitutes an autonomous region of Italy, the Regione Autonoma Siciliana Sicily has a rich and unique culture, especially with regard to the arts, music, literature,...
, codenamed "Mackerel
Mackerel
Mackerel is a common name applied to a number of different species of fish, mostly, but not exclusively, from the family Scombridae. They may be found in all tropical and temperate seas. Most live offshore in the oceanic environment but a few, like the Spanish mackerel , enter bays and can be...
". Operators of both links were in the habit of enciphering several messages with the same machine settings, producing large numbers of depths. These depths were analysed by Michael Crum.
External links
- John Savard's page on the Geheimfernschreiber
- Photographs of Sturgeon
- Entry for "Sturgeon" in the GC&CS Cryptographic Dictionary
- Bletchley Park's Sturgeon, the Fish that Laid No Eggs at The Rutherford JournalThe Rutherford JournalThe Rutherford Journal is a peer-reviewed academic journal that covers the history and philosophy of science and technology.It publishes invited articles and is edited by Jack Copeland . The journal is published annually, starting from December 2005...
.