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OTT Mixer Hotline STK
The idea for the machine came from Bjørn Rørholdt, Colonel, engineer,
veteran and liason of the Norwegian Army. In close collaboration with
Kåre Meisingset at STK,
the idea was further developed, resulting in 1952
in a patent for a new cipher machine with One-Time Tape
[1]. 1
Other NATO countries were immediately interested in this new cipher
machine and the ETCRRM soon became a standard crypto device within
NATO.
If the machine was used properly, i.e. with a truely random key tape that
would only be used once,
it was truely unbreakable.
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ETCRRM is the abbreviation of Electronic Teleprinter Cryptographic Regenerative Repeater Mixer.
The machine was developed in 1953 and 1954 by STK as an alternative to the
ageing British 5-UCO
and the American SIGTOT,
which had been in short supply since NATO was established in 1949 [6].
The machine was approved by NATO
for traffic at all levels of classification in April 1954 [7] and arguably
became one of the most popular cipher machines of the 1950s.
Three versions of the ETCRRM were manufactured over the years,
each with minor differences and improvements.
They were identified by the addition
of a Roman number (I, II and III) to the model name.
The image above shows the original ETCRRM Mark I.
At the front is a Creed 5-level paper tape reader that is affixed to
the bottom panel, but there are also version with a detached reader.
The machine was used by many NATO countries and even by non-NATO countries
such as Austria. By August 1955, the ETCRRM was being produced at a rate of
200 machines per month with a unit cost of US$ 1200 [9].
After the Cuban Missile Crisis of 1962,
the machine even became a critical components at both ends
of the Washington-Moscow Hotline.
In 1959, a synchronised version of the machine, the ETCRRM-III,
was introduced [10]. It allowed the machine to be used over unreliable
narrowband Short Wave (SW) radio channels, without loosing synchronisation
with the key tape. The machine was finally superceeded by other machines
with similar capabilities,
such as the Philips Ecolex IV
and the Siemens M-190.
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Although this patent is frequenty mentioned in literature, for example
in [1], we have not been able to find it. If anyone has access to this
patent, please contact us.
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The ETCRRM was developed by STK
as a smaller, transportable and more
affordable alternative to the Britsh 5-UCO,
which was left-over from WWII. Along with SIGTOT,
an American OTT machine, these two were the only ones that were initially
approved for NATO traffic of all classifications.
In a meeting of 13 January 1954, the lack of availability of these two machines
was reported to the chairman of the Ad-hoc Cryptographic Coordination Agency (ACCA)
of NATO, who replied that a new machine, named ETCRRM, would soon become
available to the NATO members [6].
The ETCRRM was developed during 1953 and 1954 and was finally approved
for COSMIC and NATO messages of all classifications on 19 April 1954 [7].
Alternative OTT machines were also developed, such as the
Dutch PTT/Philips Ecolex I
and the French T-53,
but neither of them ever gained the popularity of the ETCRRM.
A month later, in the first meeting of NATO's C-E Board on 21 May 1954,
the bad supply situation of cipher equipment was once more confirmed,
but this time it was announced that the first ETCRRM machines
had just been ordered by SHAPE [8].
By August 1955, the situation had improved drastically and the ETCRRM was
being produced at a rate of 200 units per month [9].
The price of a single ETCRRM unit at that time was US$ 1200, compared to
US$ 3000 - 6000 for the Ecolex
and US$ 12,000 for the 5-UCO
[9].
It should come as no surprise that the ETCRRM became the more popular
machine throughout the 1950s.
Apart from NATO and NATO-countries, it was also used by the Army of
the neutral country of Austria.
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The ETCRRM also played an important role in the Cold War.
After the Cuban Missile Crisis of 1962, it was decided to establish a
permanent direct teleprinter link
between the Kremlin in Moscow (Russia) and the
White House in Washington (US).
The hotline
became operational in 1963
and four ETCRRM machines were used on a daily basis for many years.
Each country communicated in its own language, using Teletype machines
for the English language and (modified) Siemens T-37 teleprinters
for cyrillic. The hotline was first used in 1967 during the
six-day Egypt-Israel war.
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In telegraphy, each letter (or: character) is represented by a pattern
of 5 bits, often stored on a paper tape as a series of punched holes.
Most systems follow the Baudot
standard for this. Each character from
the keyboard, or from a reader that contains the plain-text tape, is
mixed with one character from a key-tape. The key-tape contains random
characters, and the two characters are mixed bit-wise by means of an
XOR operation (modulo-2 addition). At the receiving end, a copy of the
original key-tape is mixed with the cipher-text in order to reveal the
plain-text.
As transistors were not yet available in the early 1950s, the electronic
XOR-circuits inside the ETCRRM largely consist of 12AT7 electronic valves
(tubes), some relays and selenium diodes. Some good photographs of the
interior of the machine can be found on Jerry Proc's website [3].
Although it is claimed in [1] that the principle behind the ETCRRM is a
Norwegian invention, this is unlikely. So far, we haven't been
able to find the 1952 patent of the machine, and numerous other patents for
similar devices, using the same principle, have been filed long before.
During WWII, for example, Siemens developed the
T-43,
which was also a mixer machine.
All these inventions are based completely or in part on patent US1,310,719
of 1918 by Gilbert Vernam.
➤ More about the Vernam Cipher
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We don't have this manual yet. You can help us expand this page by supplying
additional information. If you have this manual, please contact us.
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- Norwegian National Security Authority (NSM), Årsmelding 2008
NSM Annual Report 2008 (Norwegian).
Noen kryptosuksesser. p. 15.
- Wikipedia, Moscow-Washington hotline
Retrieved, June 2012.
- Jerry Proc, Electronic Teleprinter Cryptographic Regenerative Repeater Mixer
Website. Retrieved June 2012.
- NATO, ETCRRM Training Manual Edition Number 3
NATO, AFCENT, Cryptographic School. NATO Unclassified.
1961. Circuit diagrams 1954-1958.
- Crypto Museum, Washington-Moscow Hotline
Retrieved December 2013.
- NATO/ACCA, On-Line Cipher Equipments
SGM-279-54. 29 March 1954. NATO SECRET.
Declassified by NATO in 2006 (IMSM-0001-2006).
- NATO, Approval of Electronic Mixer ETCRRM
SGM-311-54. 19 April 1954. NATO SECRET.
Declassified by NATO on 17 November 1999 (IMSM-431-99).
- NATO, C-E Board 1st Meeting Minutes, dated 21 May 1945 (revised)
SGM-460-54. 25 June 1954. NATO SECRET. pp. 19-21.
Declassified by NATO on 24 November 1999 (IMSM-0431-99).
- 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).
- NATO, Synchronous ETCRRM
SGM-464-59. 12 August 1959. NATO SECRET. pp. 19-21.
Declassified by NATO on 5 January 2000 (IMSM-0431-99).
- Kevin Coleman, Photograph of BID/570/1
Website: Jerry Proc's Crypto Pages. Retrieved November 2018.
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© Crypto Museum. Created: Monday 11 June 2012. Last changed: Wednesday, 08 December 2021 - 13:06 CET.
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