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Ecolex II
One-time tape cipher machine - wanted item

Ecolex-II was an online/offline One-Time Tape (OTT) cipher machine (mixer) for teleprinter communication, developed by the Dutch Post Office (PTT) in 1958 and built by Philips Usfa in Eindhoven (Netherlands) between 1958 and 1963. It was the fully transistorized successor to the valve-based Ecolex-I. The machine is also known by its Philips Usfa designator Us 8011.

The image on the right shows three Ecolex-II units side-by-side. The rather compact devices were based on a common Siemens paper-tape reader of those days. The additional electronic circuitry was housed in a black box that was bolted to the bottom of the tape reader [1].

At the front of the unit are 6 white push-buttons, an of/off switch and three lamps: for clear, crypto and alarm). The interior of the Ecolex-II is very robust. It contains many transistors, a couple of relays, a lot of passive compoinents and many, many wires.
  

Like most other mixer machines, the Ecolex-II uses the Vernam Cipher for 'mixing' the plain text with the key tape. Each character from the plain text tape is XOR-ed with a character from the key tape. In this case, the key tape is a so-called One-Time Tape (OTT). If the key tape consists of truely random characters, and proper cipher security is maintained, the cipher is unbreakable.

Although the Ecolex-II is built to the highest quality standards, maintenance and repair must have been a real nightmare. Most electronic components are mounted vertically in between two PCBs. As they are all soldered at both ends, it is extremely difficult to get access to a component right at the center. All transistors are located on top of the upper PCB and are connected to the rest of the circuits by means of wires.

A total of 120 Ecolex-II units were built by Philips Usfa [2]. They were sold to the Dutch Army, the Dutch Ministry of Foreign Affairs and the German Ministry of Foreign Affairs [2]. On 23 May 1958, the Ecolex II was approved for NATO traffic of all classifications [6]. Just before the Ecolex-II went into production in 1959, Philips had already started its own development OTT cipher machines, resulting in the Ecolex III 1 and the Ecolex IV, both of which offered featured full synchonisation.

  1. Within NATO, the Ecolex III was known as Ecolex IIB.

Unknown device 1 Unknown device 2 Ecolex-II, photo by Jan Lispet

Help required
Crypto Musem are still looking for an Ecolex II unit for its collection. If you can help in any way, please contact us.

References
  1. Photographs from Philips Usfa
    Crypto Museum Archive.

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

  3. Philips Usfa NV, Gebruiksaanwijzing voor het Philips Usfa vercijferapparaat Ecolex II
    Ecolex II User Manual (Dutch). 2 September 1958. Declassified.
    Typenummer Us 8011/05. VTH 11-956/1. KL/GGC-3010.

  4. Koninklijke Landmacht, Ecolex II User Manual, Supplement
    Description of interoperability with Lorenz Mixer (Dutch).
    8A-II-IUB 504427. 15 April 1965.

  5. Philips Usfa, Ecolex II, US 8011, Technical Service Manual

  6. NATO, ECOLEX MARK II, Transistorized Version
    SGM-318-58. 23 May 1958. NATO SECRET.
    Declassified by NATO in 2006 (IMSM-0001-2006).
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Crypto Museum. Last changed: Friday, 28 August 2015 - 15:50 CET.
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