Everyone should have heard about involvment of Polish cryptographers in breaking Enigma. But there's another great story containing cryptography - DUDEK cipher machine.

After World War II, Polish People’s Republic was in need of system protecting undisclosed information. This task was assigned to Cipher Bureau of Ministry of Internal Affairs, so called "A" Bureau. Many years of conducting research in cryptography and cryptanalysis, development of technologies made it the most specialized unit in whole country. Its history is still not fully revealed, but we know that in 1968 Bureau contained 5 departments and 2 independent sections.

In 1964, Wielkopolskie Telecommunication Factory T-7 Teletra together with Cipher Bureau planned and developed a new cryptographic device called TgS-1 DUDEK - acronym for Dalekopisowe Urządzenie Do Elektronicznego Kodowania (Teleprinter Device for Electronic Coding).

Teletra Factory

Wielkopolskie Telecommunication Factory T-7 Teletra

For encryption and decryption, it used Vernam Cipher, developed in 1918 by Gilbert Sandford Vernam, and also known as One-Time Tape (OTT). In order to use OTT, you need 2 copies of the key (also known as pad), which have to be truely random data at least as long as the message. One copy of the key is kept by a user, second one has to be shared via secure channel, like meeting face to face. Then, to encrypt our data, we take corresponding characters of the message and pad, XOR them giving the first letter of the ciphertext and move on to the next characters. Recipient, after receaving the message has to reverse this operation - XOR each letter of ciphertext with each letter of the pad. Once used, pads must be completely destroyed to keep the security of the cipher.

Dudek Machine


The pad must be composed of truly random data, it must never be used more than once and it must be kept secure. If it's used correctly one-time pad is truely unbreakable system. But what happens when the key is used more than once?

Soviet intelligence encrypted their communications with their agents in Britain using one-time pad. Cryptanalysists from project Verona, which was a counterintelligence program initiated by the United States Army's Signal Intelligence Service, revealed that some of the one-time pad material had been incorrectly reused by the Soviets. In result, over a period of years, various secret communications were compromised.

Altough we may think that nowadays it's easy to compute random numbers, it's actually still very hard task. Current pseudo-random generators rely on the state of the machine, input-output or even network state. As a result, in practice most personal computers are not able to produce true randomness. That's where True Random Numbers Generators come in. It's a device that works on generating random numbers using physical processes such as thermal noise, quantum optics or photoelectric effects.


Example of TRNG

As we now know how Vernam Cipher works, let's come back to DUDEK. It was part of the teleprinter machine, suitable of encrypting and decrypting telegraphic character. Data could be entered manually, or using built in scanner, and it was sent with speed of 50 to 75 bits per second. Whole machine weighted 35kg with dimensions of 540x260x400mm in first version, or lighter 32kg mobile version TgS-1M with dimensions of 500x250x390mm.

  • TgS-1 - basic version known in DDR as T-352
  • TgS-1M - mobile version known in DDR as T-353
  • TgS-1MS - mobile version
  • TgS-3 - newer version introduced in 1980 which used TTL logic

Dudek Controls

Dudek Controls

Dudek Interior

Interior of Dudek machine

As opposed to other devices in the sixites, DUDEK was built using magnetic core logic building blocks of the so-called UNILOG-30 family. By using a toriod cores with several windings, it was possible to create the basic logic gates, such as AND, OR, XOR and Inverter circuits.

Dudek Circuit

Circuit of TgS-1 DUDEK

Because of it's top secret cleareance, DUDEK was used almost in every special forces of the Ministry of Internal Affairs, Ministry of Foreign Affairs, Ministry of Defence, police and the National Bank of Poland. It is known that in 1986 there were already 1070 of such devices, and it was produced up until 2000, when the last units were pulled back from the police stations.

These machines were very longevous, as they were expected to work at least 20 years. The last DUDEK was retired from a police station in 2011, while many machines still work in the museums. Unfortunately this project has to be closed, as research teams were shut, Teletra was sold to Alcatel and went bankrupt. At the same time computers and internet started to appear in Poland leading to the final decline.

Last Words

For me it's always amazing to hear such stories, especially stories that aren't widely heard even in the country of origin. That's why I wanted to write about this topic, holding together huge number of 5 references and somehow glue them together. But as always I hope you enjoyed and learned something new!


[1] Wikipedia

[2] Cyberdefence24 (PL)

[3] CryptoMuseum

[4] CSMiami