One-time tape cipher machine
- wanted item
Ecolex-II was an online/offline
One-Time Tape (OTT) cipher machine
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
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 .
At the front of the unit are 6 white push-buttons,
an of/off switch and three lamps: for clear, crypto and alarm).
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
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
They were sold to the Dutch Army, the Dutch Ministry of Foreign Affairs
and the German Ministry of Foreign Affairs .
On 23 May 1958, the Ecolex II was approved for NATO traffic of all
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.
Within NATO, the Ecolex III was known as Ecolex IIB.
Crypto Musem are still looking for an Ecolex II unit for its collection.
If you can help in any way, please contact us.
- Photographs from Philips Usfa
Crypto Museum Archive.
- Philips Usfa, Internal Memo L/5636/AvdP/JG
23 August 1982, page 5.
- 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.
- Koninklijke Landmacht, Ecolex II User Manual, Supplement
Description of interoperability with Lorenz Mixer (Dutch).
8A-II-IUB 504427. 15 April 1965.
- Philips Usfa, Ecolex II, US 8011, Technical Service Manual
- NATO, ECOLEX MARK II, Transistorized Version
SGM-318-58. 23 May 1958.
Declassified by NATO in 2006 (IMSM-0001-2006).
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