Click for homepage
← Philips
Ecolex II →
Ecolex I
One-time tape cipher machine - wanted item

Ecolex I was an valve-based online/offline cipher machine for teletype communication, developed by the Dutch Post Office (PTT) around 1953 and built by Philips Usfa in Eindhoven (Netherlands) between 1953 and 1958. It was the first one-time tape (OTT) cipher machine (mixer) that was completely developed in The Netherlands as an alternative to the Norwegian ETCRRM and the British 5-UCO that were in use by NATO at the time. Ecolex I was approved for NATO traffic.

As far as we know, there are no surviving Ecolex I machines and the photographs presented on this page are probably the only ones left.

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
1 / 6
Complete setup (without the PSU)
2 / 6
Ecolex-I with tape reader
3 / 6
Complete setup (with the PSU)
4 / 6
Power Supply Unit
5 / 6
6 / 6

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 increased drastically. 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].

Around the same time (1952/53) the Dutch Post Office (PTT) started its own development of a mixer machine (OTT), probably at the request of the Dutch Government. 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 wasn't until 12 August of the next year that the two machines were approved for COSMIC messages and NATO messages higher than CONFIDENTIAL [5].

As the Dutch PTT did not have its own production facilities, the Ecolex I was built at Philips Usfa in Eindhoven (Netherlands), which was already a strong contract partner of the Dutch Department of Defense (DoD) since 1949. The machine was in production until 1958 and in total only 25 units were built before it was succeeded by the much smaller and fully transistorised Ecolex II.

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]. Needless to say that the ETCRRM won this race.

  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.

  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).
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: Thursday 13 June 2013. Last changed: Saturday, 24 February 2018 - 15:28 CET.
Click for homepage