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Ecolex I
One-time tape cipher machine - wanted item

Ecolex I was an online/offline One-Time Tape (OTT) cipher machine for teletype communication, developed and built by the Dutch Post Office (PTT) around 1953. Between 1956 and 1958, it was built by Philips Usfa in Eindhoven (Netherlands). The device was based on Colex, the first Dutch mixer, but was built with thermionic valves (vacuum tubes) rather than electromechanical relays. It was an alternative to the British 5-UCO machine and was approved for all level of NATO traffic.

As far as we know, only one Ecolex I specimen has survived. It is currently held in an internal collection of the Dutch Department of Defense.

The image on the right shows a complete setup, consisting of a Siemens T-37 teleprinter at the left, a double Siemens paper-tape reader at the center and the Ecolex-I system itself at the right. The large power supply unit, was unually hidden under the table. The Ecolex is based on the well-known principle of the Vernam Cipher, which is implemented here with no less than 69 valves.
  
Complete setup (without the PSU)

Initially, the Ecolex I (or 'Ecolex' as it was called at the time) was used by the Dutch Department of Defense (DoD) for military traffic, and by the Dutch Foreign Office for diplomatic traffic at the highest level of classification. It was later also offered to NATO and to other NATO countries, but lost the race to the Norwegian ETCRRM machine. In total, only 25 Ecolex I machines were ever built [2]. The machine was succeeded in 1958 by the fully transistorized Ecolex II.

One-time tape machines like the Ecolex I are in theory unbreakable if, and only if, the keystream tape is truely random. In practice however, the tapes were often generated by other (mainly mechanical) pseudo-random number generators (PRNG) and were therefore less secure. For this reason, the Dutch PTT developed its own truely random noise generator: the EROLET.

Complete setup (without the PSU)
Ecolex-I with tape reader
Complete setup (with the PSU)
Power Supply Unit
Interior
Interior
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Complete setup (without the PSU)
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Ecolex-I with tape reader
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Complete setup (with the PSU)
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Power Supply Unit
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Interior
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Interior

History
In the years following WWII, the countries of the Western Union (WU) had a growing need for secure military and diplomatic communications equipment. After the WU had been dissolved into the newly established NATO (1949), the need for secure communication became even more important. Initially, only the British 5-UCO, a left-over from WWII, was available for this, but the British were unable to supply it in sufficient quantities to fulfill the needs. Apart from that, the 5-UCO was a rack-based solution that was way too large to be of any practical use in the field.

In 1953, the Norwegian company STK tried to fill the gap by developing the ETCRRM, a valve-based OTT machine that was much smaller than the 5-UCO and easily fitted a table top. After several improvements, SECAN approved the ETCRRM for use by NATO on 19 April 1954 [3].

Several years earlier, in 1946, the Dr. Neher Laboratory of the Dutch Post Office (PTT) had started the development of a One-Time Tape machine at the request of the Dutch Government. Due to shortages in electronic components in the first years after WWII, it was built with approx. 100 electromechanical relays. The machine was named Colex, and was a development of Dr. Ir. Roelof Oberman, who would later become Professor at Delft University. A small number of these Colex machines were commissioned on 6 April 1949 for communication between the Dutch Foreign Office and its embassies in London (UK), Paris (France), Washington (USA) and Jakarta (Indonesia).

Colex was not a fast machine – it could only handle three characters per second – but its success resulted in the development of its successor: Ecolex — which is short for Electronic Codetelex. As the PTT was not interested in the commercial exploitation of the machine, the production was transferred to Philips Usfa, where it became known as Ecolex I. The machine was ready in mid-1953 and existed in two variants: Ecolex Mark I and Mark II. 1 A description was sent to NATO on 4 August 1953 [4], but it was not until 12 August of the next year that the two machines were approved for COSMIC traffic and for NATO traffic higher than CONFIDENTIAL [5].

The price for a single Ecolex Mark I unit in 1955 was US$ 6000 and for an Ecolex Mark II unit 'just' US$ 3000, 1 with a lead time of 12 and 11 months respectively. The ETCRRM on the other hand was produced at a rate of 200 units per month and was available immediately at a unit price of just US$ 1200 [6]. ETCRRM therefore won the race. Ecolex I was in production until 1958, and a total of just 25 units were built before it was succeeded by the smaller transistorised Ecolex II.

  1. Mark I and Mark II should not be confused with Ecolex I and Ecolex II which are two entirely different machines. Mark I and Mark II are two variants of the Ecolex I which was simply called 'Ecolex' back then. The differences between the two variants are currently unknown.

Documentation
  1. Ecolex I, User manual (French)
    Date unknown, but probably 1953. 1

  2. Ecolex Mark I and II
    The Netherlands Government, 1 October 1954. SECRET. 1
  1. Document kindly provided by Maarten Oberman [7].

References
  1. Photographs from Philips Usfa
    Crypto Museum Archive.

  2. Philips Usfa, Internal Memo L/5636/AvdP/JG
    23 August 1982, page 5.

  3. NATO, Approval of Electronic Mixer ETCRRM
    SGM-311-54. 19 April 1954. NATO SECRET.
    Declassified by NATO on 17 November 1999 (IMSM-431-99).

  4. NATO, Netherlands On-Line Cipher Equipment
    SGM-1254-53. 17 August 1953. NATO SECRET.
    Declassified by NATO in 2006 (IMSM-0001-2006).

  5. NATO, Approval of Electronic Mixers ECOLEX Mk I and II
    SGM-556-54. 12 August 1954. NATO SECRET.
    Declassified by NATO in 2006 (IMSM-0001-2006).

  6. NATO, Automatic Crypto-Equipment Requirements for the Allied Command Atlantic
    SGM-560-55. 15 August 1955. NATO SECRET.
    Declassified by NATO on 24 November 1999 (IMSM-0431-99).

  7. Maarten Oberman, Personal correspondence
    June 2019. Crypto Museum, RMM Oberman archive.
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Crypto Museum. Created: Thursday 13 June 2013. Last changed: Monday, 11 January 2021 - 20:13 CET.
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