Роторная шифровальная машина TSEC/KL 7: История и особенности

Rotor encryption machine

The TSEC/KL 7, also known as Adonis The KL 7 had rotors to encrypt the text, most of which moved in a complex pattern, controlled by notched rings. The non moving rotor was fourth from the left of the stack. The KL 7 also encrypted the message indicator.

In 1945, the Army Security Agency (ASA) initiated the research for a new cipher machine, designated MX 507, planned as successor for the SIGABA and the less secure Hagelin M 209. In 1949, its development was transferred to the newly formed Armed Forces Security Agency (AFSA) who named the machine AFSAM 7, which stands for Armed Forces Security Agency Machine No 7. It was the first rotor crypto machine, developed under one centralized cryptologic organisation as a standard machine for all parts of the armed forces, and the first cipher machine to use electronics (vacuum tubes), apart from the British ROCKEX, which was developed during World War 2. It was also the first cipher machine to use the re entry (re flexing, not to be confused with reflector) principle, conceived by Albert W. Small, which re introduces the encryption output back into the encryption process to re encipher it again, so that some symbols are ciphered more than once. In 1953, AFSA's successor, the U. S. National Security Agency, introduced the machine in the US Army and Air Force, the FBI and CIA. In 1955, the AFSAM 7 was renamed TSEC/KL 7, following the new standard crypto nomenclature. It was the most widely used crypto machine in the US armed forces until the mid 1960s and was the first machine capable of supporting large networks that was considered secure against known plaintext attack. Some 25,000 machines were in use in the mid 1960s.