Krypto wireless teleprinter 58, KFF-58; made by Dr. Edgar Gretener AG, Zurich.
Because of the Telekryptogeräte 53 fell out of sync quite often - especially when radio communication was used - Dr. E. Gretener developed an improved successor model, which essentially consists of an ETK-50 R and the cipher part of the Telekrypto 53 with automatic synchronization:
So the Swiss Army got one of the world's best wireless cipher teleprinter with real - time encryption in those years, when the KFF 58 was introduced.
- Mains: 220 V (100 - 265 V) AC mains
- Teleprinter unit (in case): 320 x 660 x 600 mm, 69 kg
- Cipher unit (in case): 340 x 610 x 340 mm, 28 kg (classified)
total: 97 kg
- LU-68: Lochstreifenumsetzer (perforated tape converter) 68
The Krypto wireless teleprinter 58 consists of the printer unit and the keyboard very similar to the one found in the „single tone combination teleprinter“ ETK with its fourteen element characters. In contrast to the CCITT No.2 baudot code, messages with a missing segment remain often readable - like in a seven-segment display when only one dash is missing - and characters will not be replaced by other characters.
The actual encryption takes place in the cipher unit mounted on top of the teleprinter unit. Only the cipher unit was classified as „secret“.
The message key consists of a letter key of 12 letters and a number key of 4 out of 8 numbers. The four permutation wheels on the left side and the stepping wheels visible on the right side of the key window are advanced electrically to the starting position with up/down switches, then the numbered levers 1-8 switched to top position according to the number key.
The breakthrough of the KFF-58 was its „SYN KRYPTO“ mode: The machines at the transmitter and receiver side are constantly kept synchronized by synchronizing pulses, even when no characters are transmitted. If the synchronization pulses fail due to radio propagation disturbances, the synchronization is provided by an internal quartz oscillator, so that short transmission failures can be bridged for up to several minutes without the machines coming out of sync.
The transmission is synchronous, the characters are printed asynchronously; to bridge the time difference, two characters (twice 14 bits) must be stored. In the original version, the storage was done electromechanically by means of relays, in the 1968 version the 2 x 14 bit memory was replaced by an electronic memory.
The KFF-58 is also equipped with the round [SPG], the key production device, which is not much more than a random letter generator that generates a random message key.
Automatic cipher machine using vernam ciphering and automatic synchronisation.
Due to the fact, that the KFF-58 uses the fourteen-element alphabet of the ETK, it could not work together with other cipher devices or teletypewriters. The KFF-58 was withdrawn in 1991.
The cipher units (with the cipher wheels) were almost completely liquidated, in this case, this means they were destroyed. The teleprinter units were sold in the context of army surplus liquidations.