Click for homepage
DUDEK TgS-1   T-352
One-time tape cipher machine - wanted item

TgS-1, or DUDEK, was a One-Time Tape (OTT) cipher machine, or mixer, developed in the 1960s by Wielkopolskie Zakłady Teletechniczne Teletra T-7 (Wielkopolskie Telecommunication Work, Plant number T-7) in Poznan (Poland) for Bureau A of the Polish Interior Ministry (MSW) 1 [1]. DUDEK means Dalekopisowe Urządzenie Do Elektronicznego Kodowania (Teleprinter Device for Electronic Coding). It was approved by the MSW for messages up to the level of TOP SECRET [2].

The Dudek was suitable for teleprinter networks (telex) and supported a data transmission speed (baud rate) of 50 to 75 bits per second (baud). It was used in combination with teleprinters like the Siemens/Ceska T-100 and the RFT T-51.

For encryption and decryption it uses a built-in 5-level tape reader that mixes each character of the 5-bit teleprinter signal with one character from a random key tape, by means of an XOR circuit. In cryptography, this principle is known as Module-2 or Vernam Cipher and was invented in 1918 in the US by Gilbert Sandford Vernam.

Dudek (TgS-1) was used in Poland by the Ministry of the Interior, the Ministry of Foreign Affairs, the Ministry of Defence, the police and the National Bank of Poland. The machine was also used by the cryptographic services of other Warsaw pact states, for example by the Ministry of State Security (Stasi) of the former German Democratic Republic (DDR), where it was known as T-352.

The TgS-1 was build with torid core logic (see below) and the mobile version was designated TgS-1M (in the DDR known as T-353). In the late 1970s, the TgS-1 was succeeded by the improved TgS-3 that was build around TTL-based logic Integrated Circuits (ICs) and had an improved data transfer rate. The last Dudek was decommissioned in Poland in January 2011. 2

  1. MSW is the Ministerstwo Spraw Wewnętrznych (Ministry of the Interior) of Poland, and is an adminitrative structure responsible for internal security, law enforcement, civil defence and registry functions [6].
  2. The last machine that was decommissioned, was in use by the Polish Police (Policja) [2].

DUDEK TgS-1M (T-353) on top of Siemens/Ceska T-100 teleprinter
DUDEK TgS-1 next to an RFT teleprinter
T-353, the DDE-version of the DUDEK TgS-1M
TgS-1M (T-353) interior seen from the top
Close-up of a PCB with core logic building blocks
Front view of the T-353 (TgS-1M)
Close-up of the data rate selector (50/75 baud)
T-353 (TgS-1M) next to an RFT teleprinter in the days of the DDR
1 / 8
DUDEK TgS-1M (T-353) on top of Siemens/Ceska T-100 teleprinter
2 / 8
DUDEK TgS-1 next to an RFT teleprinter
3 / 8
T-353, the DDE-version of the DUDEK TgS-1M
4 / 8
TgS-1M (T-353) interior seen from the top
5 / 8
Close-up of a PCB with core logic building blocks
6 / 8
Front view of the T-353 (TgS-1M)
7 / 8
Close-up of the data rate selector (50/75 baud)
8 / 8
T-353 (TgS-1M) next to an RFT teleprinter in the days of the DDR

The image below shows the T-353 (TgS-1M) seen from the front top. The unit is about the width of a teleprinter and is suitable for placement on a table top. The connections, fuses and the meter are all at the lower section of the front panel (not visible here). The rest is pretty straightforward.

The upper half of the front panel roughly consists of three sections: a 5-level paper tape reader at the left, used for the key-stream tape, a control panel at the centre and another 5-level paper tape reader at the right, used for the input. DUDEK is suitable for both online and offline use.

Unlike other digital systems in the early 1960s, which either used valve-based or transtor-based logic, the DUDEK is built around 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, but also more complex circuits like a flip-flop.

As magnetic core logic is significantly different from valve-based or transistor-based logic, the designers used their own electronic symbols, which makes the circuit diagram a little bit more difficult to understand [6].

The image on the right shows an example of a logic circuit board inside the DUDEK. A good description of the internal hardware of the DUDEK and the core logic circuit on which is was built, can be found on Jörg Drobick's website [4].

 More on Jörg Drobick's website


  • TgS-1
    Basic version, in the DDR known by Stasi-designator T-352
  • TgS-1M
    Mobile version, in the DDR known by Stasi-designator T-353
  • TgS-1MS
    Mobile version
  • TgS-3
    Newer version with TTL logic, developed in the late 1970s
DDR versions
    Latin version for national and international traffic
    Cyrillic version
    Cyrillic version for the East German PTT
  1. ZCO, Gebrauchsanweisung zum Verfahren DUDEK
    GVS-ZCO/57/74. MfS-Abt.XI-192-BV. User Manual (German). 1 July 1974.

  2. MSW, Chiffriergerät TgS-1M, Betriebsvorschrift
    Band I, Technische Beschreibung. Band II, Schatbilder u. Leitungspläne.
    121/I-201-083 N. MfS-Abt.XI-659. Technical Manual (German). 1975.
  1. Many thanks to Jorg Drobick [4] for supplying the manuals and the photographs of the T-353/StG-1.

  1. Wikipedia (Polish), TgS-1 Dudek
    Retrieved Januari 2015.

  2. Wikipedia (English), DUDEK
    Retrieved Januari 2015.

  3. Jan Bury, For the Archives: Inside a Cold War Crypto Cell.
    Polish Cipher Bureay in the 1980s

    Cryptologia 32 (4), October 2008, pp. 351-367.

  4. Jorg Drobick, T-352 / T-353 DUDEK
    Website (German). Retrieved Februari 2015.

  5. DUDEK, TgS-1, Circuit Diagram detail
    BStU, MfS, Abt XI Nr. 000659. Retrieved February 2015.

  6. Wikipedia, Ministry of Interior (Poland)
    Retrieved August 2015.
Further information
Any links shown in red are currently unavailable. If you like the information on this website, why not make a donation?
Crypto Museum. Created: Monday 02 February 2015. Last changed: Friday, 23 February 2018 - 22:18 CET.
Click for homepage