cryptography Cryptography, or cryptology (from "hidden, secret"; and ''graphein'', "to write", or ''-logy, -logia'', "study", respectively), is the practice and study of techniques for secure communication in the presence of Adversary (cryptography), ...

, Fialka (M-125) is the name of a

Cold War The Cold War was a period of global Geopolitics, geopolitical rivalry between the United States (US) and the Soviet Union (USSR) and their respective allies, the capitalist Western Bloc and communist Eastern Bloc, which lasted from 1947 unt ...

-era

Soviet The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...

cipher machine. A

rotor machine In cryptography, a rotor machine is an electro-mechanical stream cipher device used for encrypting and decrypting messages. Rotor machines were the cryptographic state-of-the-art for much of the 20th century; they were in widespread use from ...

, the device uses 10 rotors, each with 30 contacts along with mechanical pins to control stepping. It also makes use of a

punched card A punched card (also punch card or punched-card) is a stiff paper-based medium used to store digital information via the presence or absence of holes in predefined positions. Developed over the 18th to 20th centuries, punched cards were widel ...

mechanism. ''Fialka'' means " violet" in

Russian Russian(s) may refer to: *Russians (), an ethnic group of the East Slavic peoples, primarily living in Russia and neighboring countries *A citizen of Russia *Russian language, the most widely spoken of the Slavic languages *''The Russians'', a b ...

. Information regarding the machine was quite scarce until c. 2005 because the device had been kept secret. Fialka contains a five-level

paper tape Five- and eight-hole wide punched paper tape Paper tape reader on the Harwell computer with a small piece of five-hole tape connected in a circle – creating a physical program loop Punched tape or perforated paper tape is a form of data st ...

reader on the right hand side at the front of the machine, and a paper tape punch and tape printing mechanism on top. The punched-card input for keying the machine is located on the left hand side. The Fialka requires 24 volt DC power and comes with a separate

power supply A power supply is an electrical device that supplies electric power to an electrical load. The main purpose of a power supply is to convert electric current from a source to the correct voltage, electric current, current, and frequency to power ...

that accepts power at 100 to 250 VAC, 50–400 Hz by means of an external selector switch. The machine's rotors are labelled with

Cyrillic The Cyrillic script ( ) is a writing system used for various languages across Eurasia. It is the designated national script in various Slavic, Turkic, Mongolic, Uralic, Caucasian and Iranic-speaking countries in Southeastern Europe, Ea ...

, requiring 30 points on the rotors; this is in contrast to many comparable Western machines with 26-contact rotors, corresponding to the

Latin alphabet The Latin alphabet, also known as the Roman alphabet, is the collection of letters originally used by the Ancient Rome, ancient Romans to write the Latin language. Largely unaltered except several letters splitting—i.e. from , and from � ...

. The keyboard, at least in the examples of East German origin, had both Cyrillic and Latin markings. There are at least two versions known to exist, the M-125-MN and the M-125-3MN. The M-125-MN had a typewheel that could handle Latin and Cyrillic letters. The M-125-3MN had separate typewheels for Latin and Cyrillic. The M-125-3MN had three modes, single shift letters, double shift with letters and symbols, and digits only, for use with

code book A codebook is a type of document used for gathering and storing cryptography codes. Originally, codebooks were often literally , but today "codebook" is a byword for the complete record of a series of codes, regardless of physical format. Cr ...

s and to superencrypt numeric ciphers.

Encryption mechanism

The Fialka rotor assembly has 10 rotors mounted on an

axle An axle or axletree is a central shaft for a rotation, rotating wheel and axle, wheel or gear. On wheeled vehicles, the axle may be fixed to the wheels, rotating with them, or fixed to the vehicle, with the wheels rotating around the axle. In ...

and a 30 by 30

commutator In mathematics, the commutator gives an indication of the extent to which a certain binary operation fails to be commutative. There are different definitions used in group theory and ring theory. Group theory The commutator of two elements, ...

(Kc 30x30). The commutator consists of two sets of 30 contact strips set at right angles to each other. A punched card is placed between the two sets of contacts via a door on the left hand side of the unit. Each punched card has 30 holes, with exactly one hole per row and column pair, and thereby specifies a

permutation In mathematics, a permutation of a set can mean one of two different things: * an arrangement of its members in a sequence or linear order, or * the act or process of changing the linear order of an ordered set. An example of the first mean ...

of the 30 rotor contact lines. This feature is comparable to the plug board on the

Enigma machine The Enigma machine is a cipher device developed and used in the early- to mid-20th century to protect commercial, diplomatic, and military communication. It was employed extensively by Nazi Germany during World War II, in all branches of the W ...

, but is much stronger as it offers full permutation of the contacts as opposed to the pairwise swapping of letters on the Enigma. A triangular plate was used to enter the null permutation for testing purposes. There are two types of rotors: *disassemblable (''zerlegbar'') rotors, used with the M-125-3MN. The rotorset name is "PROTON." The disassemblable rotors consist of an insert with electrical contacts and scramble wiring, and an outer ring with mechanical pins whose presence or absence control rotor stepping. As part of the key setup, the stepping control pins can be rotated relative to the outer ring. The inner, electrical ring can also be rotated relative to the outer ring and can be inserted in one of two ways, with side 1 or side 2 up. *unitary rotors, used with the M-125-MN. These have both electrical contacts and mechanical pins. The only key adjustment is the order of the rotors on the axle and the initial rotor settings. There is one combination for the disassemblable rotors that is compatible with the unitary rotor. One East German manual that has become public contains typed-in and hand written addenda that suggest the East Germans, at least, later stopped using the added features of the disassemblable rotors and only used them in unitary compatibility mode. Adjacent rotors step in opposite directions. A spare rotor assembly could be kept in the unit's top cover. The Fialka machines were originally delivered with two sets of rotors, one with black lettering in the machine assemblage, and one set with red lettering supplied in a metal cylinder inside the dustcover. The singly most crucial flaw in the Enigma design was that letter substitutions were reciprocal and that in particular a letter could never encrypt to itself. The Russians clearly learned from this in designing Fialka such that it is possible for a letter to encrypt to itself. Other weaknesses of Enigma, such as the regular stepping of the wheels and limited effect of the plugboard were also improved on Fialka.

Keying material

The keying material for the Fialka consists of a daily key book, a message key book and a message identifier book for broadcast traffic. The daily key book contains day keys for one month. A day key consists of a key table (in Cyrillic) and a punched card. For fixed rotor systems, the key table specifies the order of the rotors on the axle and the initial rotor settings to be used to decrypt the indicator of broadcast messages. As its name implies, the day key is valid (has a

cryptoperiod A cryptoperiod is the time span during which a specific cryptographic key is authorized for use. Common government guidelines range from 1 to 3 years for asymmetric cryptography, and 1 day to 7 days for symmetric cipher traffic keys. Factors to co ...

in NSA parlance) for 24 hours and was changed at 00:01 hours. For the disassemblable rotors, the table also specifies the electrical insert for each outer rotor, which side was to be up, and the orientation of the insert relative to the outer rotor. Here is a sample M-125-3NM day key table for use on the 14th of the month: :ИДЖЗА ВКБГЕ 14 :OCAHE PTБВЕ :БДВИА ГЕЗКЖ :2II22 I22I2 :КУЛКЮ ЫХВУГ The message key table contained the initial rotor settings to be used with each message. A message key was never to be used more than once. The keying material was distributed in a foil-covered package, with the daily key tables and punched cards fan-folded in a pouch with perforations between each item. The other tables were in a side pouch.

Design measures against information leakage

Design factors in various cryptographic devices can result in the physical leakage of information that may compromise the security of the system to varying degrees. This is commonly known as side-channel leakage or TEMPEST. The following describe appropriate counter measures that were taken in the design of Fialka.

Power supply unit

Fialka draws differing amounts of current depending on which (5-bit) encoded letter is printed or paper punched. If the power supply was plugged into the mains there would be an opportunity for the small power fluctuations to be observed by an eavesdropper. In order to mask any mains supplied power fluctuations a data cable fed back from the Fialka machine to the power supply unit (PSU) indicating which letter was being output allowing the supply to compensate for the differing loads. The PSU was designed with a compensating circuit with five artificial load resistors which would be powered depending on the signal from the feedback cable. In addition to this, the PSU injects a strong noise signal into the power line, to further mask any remaining glitches or transient effects which could compromise the cipher.

Comparison with other rotor machines

The Fialka design is derived from contemporary rotor-based cipher machines, such as Enigma, the Swiss

NEMA The National Electrical Manufacturers Association (NEMA) is the largest trade association of electrical equipment manufacturers in the United States. Founded in 1926, it advocates for the industry and publishes standards for electrical product ...

and the American KL-7. NEMA only had 5 electrical rotors vis-à-vis the Fialka's 10, and furthermore NEMA lacked a punched card commutator or equivalent such as a plug board. Fialka is most comparable to the U.S. KL-7 which has eight electrical rotors and also lacks a commutator, but its keyboard permutation switch eliminated the need for a reflector (which had proven to be a weakness in the Enigma system).

References

External links

M-125 Fialka
— Crypto Museum
The M-125-3 Fialka cipher machine
— German Spy Museum Berlin

— by Nick Gessler

— by Jerry Proc {{Cryptography navbox , machines Cryptographic hardware Rotor machines Science and technology in the Soviet Union Soviet inventions KGB Communications in the Soviet Union Warsaw Pact