KL-7

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A KL-7 on board the museum ship HMS Belfast

The KL-7 ( aliases : "Adonis" and "Pollux") is a rotor key machine that was developed in the late 1940s by the United States National Security Agency ( ASA and AFSA , which became the NSA in 1952 ). It is the successor to the SIGABA, which was used by the US armed forces for the secret exchange of messages during World War II .

There are two different models of the KL-7. The “Pollux” model uses eight rotors and was intended for the encryption of less sensitive messages. The “Adonis” model, on the other hand, works with twelve rotors and is used to encrypt highly sensitive information. The KL-7 entered service in 1952 and was one of NATO's most important cipher machines for many years until the mid-1960s . It was not finally decommissioned until 1983.

function

Similar to other rotor cipher machines used in World War II or shortly thereafter, such as the German Enigma , the British TypeX or the Swiss Nema , the plain text to be encrypted or the ciphertext to be decrypted was entered manually into the machine via a keyboard. The KL-7 also offered the option of reading in the text using a punched tape. The comparable through the machine or decrypted text was printed on a narrow strip of paper then with glue , for example, on telegraph forms was stuck.

construction

Left and right side of a roller Left and right side of a roller
Left and right side of a roller
The set of rollers of the KL-7 contains twelve different rotors, which were marked with the letters “A” to “L”. The letter "K" can be seen next to the hub of the rotor at the top right in the picture . Contrary to what is written on the label below, they actually had 36 (and not just 26) contacts.

The machine has a set of eight rotors (“Pollux”) or twelve rotors (“Adonis”), each with 36 electrical contacts on each side , which are irregularly connected to each other in pairs by insulated wires inside the rotors. In contrast to the older machines mentioned with only 26 contacts, the KL-7 can encode not only the 26 capital letters of the Latin alphabet , but also the ten digits . Also unlike the Enigma, the KL-7 does not use a reverse roller and thus avoids one of the main cryptographic weaknesses of the German machine. Instead, the KL-7 has a switch with which the user selects the operating mode. The switch has four positions:

  • O for off (Off)
  • P for plain text (clear text)
  • E for encoding (encryption)
  • D for decoding (decrypting)

The secret key for encrypting or decrypting messages is formed by the order in which the rotors are arranged in the machine and their starting position.

literature

Web links

Individual evidence

  1. ↑ TSEC / KL-7 Simulator v5.0 (English). Retrieved July 7, 2016.