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ETCRRM
On-line mixing cipher machine - wanted item

ETCRRM was one of the first On-line cipher machines in the mixer class. It was manufactered in the early 1950s by Standard Telefon og Kabelfabrik A/S (STK) in Norway. It used electronic valve-based circuits to mix clear text with random characters from a key tape, using the Vernam principle. ETCRRM was used for many years by the US on the Washington-Moscow hotline.
 
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].

Other NATO countries were immediately interested in this new cipher machine and 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.

Three different 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 on the right shows a typical ETCRRM-II.

A standard Creed paper tape reader is mounted to the front panel of the machine, but there are also versions where the reader is detached. The key tape is fed into the reader from a reel that is mounted to the right of the machine.
  

ETCRRM also played an important role in the Cold War. After the Cuban Missile Crisis in 1962, it was decided to establish a permanent direct telex line between the White House in Washington (USA) and the Kremlin in Moscow (Russia). 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 (modified) Siemens T-37 teleprinters. The hotline was first used in 1967 during the six-day Egypt-Israel war. It was upgraded with more modern equipment in 1976 [2].
 
ETCREM machine next to a Lorenz Mizer (LOMI) Control panel of the ETCRRM ID plate of an ETCRRM-II

 
Vernam Cipher
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 1919 by Gilbert Vernam.
 
Similar machines

References
  1. Norwegian National Security Authority (NSM), Årsmelding 2008
    NSM Annual Report 2008 (Norwegian). Noen kryptosuksesser. p. 15.

  2. Wikipedia, Moscow-Washington hotline
    Retrieved, June 2012.

  3. Jerry Proc, Electronic Teleprinter Cryptographic Regenerative Repeater Mixer
    Website. Retrieved June 2012.

Further information

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