Siemens & Halske T43

from Wikipedia, the free encyclopedia

The Siemens & Halske T43 , English code name Thrasher ( " Drescher "), a teleprinter from the Second World War , by the company Siemens & Halske (now Siemens AG ) for the German Wehrmacht , especially for the Navy and the Air Force developed has been. The official designation was "T43 key teleprinter" (SFM T43), the 43 indicating the year 1943 of the development. Similar to the T52 also developed by Siemens and the Lorenz key addition SZ 42 , which was mainly used by the army , the SFM was used to enable an encrypted radio telex connection. Above the Enigma machine , which is still used for tactical communication , it served for the secret transmission of strategic communications.

functionality

To transmit a telex, the characters in the text to be transmitted are first converted into the Baudot code . As a result of this conversion, the data is now available as a sequence of 5-bit words. In the T43, each 5-bit word of the plain text was combined bit-by-bit with another 5-bit word via the XOR operation with the aid of a mixer before being sent . After receiving a character, the receiver carried out the same XOR operation on its side and thereby received the original 5-bit word again.

The 5-bit word required to encrypt or decrypt each plaintext character was read from a punched tape on the transmitter and receiver side . To prevent repeated use of the perforated tape, every bit pattern used in the context of encryption or decryption was automatically made unusable by punching out all five bit positions. If the content of the punched tape was chosen at random, the T43 offered the possibility of using the theoretically unbreakable one-time pad method. This distinguishes the T43 from machines such as T52 and SZ 42, in which the bit patterns combined with the plaintext were generated by a mechanical pseudo-random generator .

history

It is believed that the system, code-named "Thrasher" in Bletchley Park , was the T43. The Allies were unable to break into Thrasher , although this would have been theoretically possible, because according to Pröse, the punched tape data of the T43 was not generated by chance, but by combining the output of two T52e machines.

According to Pröse, another weak point of the T43 was the fact that the plain text could be reconstructed from the encrypted teletype signal using an oscilloscope . That is why the cryptologists of the High Command of the Wehrmacht recommended the use of the T43 only when using an "equalizer" at the same time. The information about the T43 that is undoubtedly in the Allied archives has not been made public to this day.

The key machine 5-UCO , which can be seen as a cryptographic counterpart to the T43, was also used on the British side during the Second World War .

literature

Web links

Individual evidence

  1. ↑ Michael Pröse: Encryption machines and deciphering devices in World War II , p. 90.