Soviet / Russian Identification Friend or Foe (IFF) Kremnij-2 and Parol http://www.mil-airfields.de/equipment/soviet-russian-iff-kremnij-parol.htm Below I have summarized my research and knowledge about the soviet/russian IFF systems “Kremnij” and “Parol”. The information originates from various sources, all of which are given below (see /1/, /2/ etc.). Since the sources go into detail at different topics and are difficult to access for technical and language reasons, I compiled all the important information for a basic understanding here.
Kremnij-2 / Кремний-2 Overview
Kremnij-2 is an IFF system which was probably developed in the 1950s. The signal of an interrogating station must be answered with the correct code. For the code, there are 12 possibilities that are modulated to the response signal. The security of the system is based on the secrecy of the then valid code that was changed in hours. There are three interrogation modes in which the interrogation signal is sent on one or two frequencies. When making an interrogation interrogation on two frequencies, the signal of the primary radar is jointly used, to which the IFF system is coupled. Kremnij-2 uses three frequency ranges: - Frequency range I: primary radar 8600. .9700 MHz - Frequency Range II: Primary radar 2520. .3380 MHz - Frequency Range III: Interrogation and response frequency 668 MHz /1/ The frequency range II was put out of service by the East German forces in the early 1980s /12/ Interrogation modes according to /1/:
I assume that „Interrogation 3“ is the so-called "Autonomous "Autonomous Interrogation", because it can also be used independently independently of a primary radar (although the synchronization synchronization with the primary radar is still needed to ensure a consistent presentation).
On the screen, a target with IFF is shown by a parallel bar on the far side /1/, /3/, /8/
General Identification (Mode I in the frequency range III)
First, there were 12 frequencies which can be used to code the response signal /1/ 1: 1,67 Mcs
7: 5,67 Mcs
2: 3: 4: 5: 6:
8: 6,33 Mcs 9: 7,00 Mcs 10: 7,67 Mcs 11: 8,33 Mcs 12: 9,00 Mcs
2,33 Mcs 3,00 Mcs 3,67 Mcs 4,33 Mcs 5,00 Mcs
In discussion forums, it is occasionally discussed whether there have been 12 more code filter for war time use /4/, /5/ Pulse diagram of the response signal according to /1/:
It seems that there was a change over time: /3/ specifies 36 possible codes, which consist of only 6 different frequencies, but with 6 additional combinations for the time positions T1 and T2 of two following response codes:
In /11/ there is a hint that also indicates a variable timing of the response code: This manual states “numbers of the pulse intervals”.
Check Code
(Other names: Kremnij-2M /2/, 81Э or 81Ä, Interrogation K, Additional Code) The response signal of the system Kremnij-2 can easily be imitated by an enemy, because there are only 12 different codes. Therefore, the possibility of a check code / additional code was introduced (in the East German forces in the early to mid 1980's /12/) The reaction to the check code interrogation must by activated manually at the transponder (e.g. by the pilot of the aircraft), triggered by a code word sent over the radio. When the check code is interrogated by an additional fourth pulse, an activated transponder recognizes this pulse and doesn't send a response. Only the imitation units of the enemy continue to answer and are still shown on the screen with an IFF signal. Pulse diagram of the query according to /3/
Using the check code was only allowed when it was ordered /10/, presumably to keep the system secret until war time. Veterans say that the check code in planes could be turned on and off, but without additional coding / 4/ /5/. Perhaps this has changed over time: /11/ from the year 1990 says "changing code of the check code of aircraft" and directs to use code no. 0 for the check code until different order. Individual Identification (mode III in the frequency range III)
For individual the identification, I found the following statements: - The individual identification was displayed on the screen in the form of Morse code or letters /5/ - To set up the individual identification, a three-digit code is used /11/ In clear contradiction is a statement in /3/: It describes that the individual identification has only one additional pulse that follows the general identification. This additional pulse can have two positions in time, so there are two possible codes. Pulse diagram of the individual identification according to /3/:
This signal seems to correspond more to the SPI ("ident") of the civilian secondary radar.
Distress Signal
For the distress signal, the frequency-coded signal of the general identification is repeated. Therefore, the distress signal is bound to the correct setting of the code frequency, i.e. when the code is set incorrectly, the distress signal is not shown on the radar screen. Pulse diagram according to /1/ /3/
A target with distress signal is shown on the screen with a bold bar /3/, /8/
Parol / Пароль Overview
Parol is the successor system to Kremnij-2. Using cryptographic methods, a much better imitation security is achieved. In the late 1980s, introduction to the East German forces began. For compatibility reasons, many Parol ground systems still support Kremnij in the frequency range III. A new addition is the frequency range VII: - 1532 Mcs: Interrogation - 1470 Mcs: Response - 1458 Mcs: Response So in this range, two response frequencies are used /2/ General Identification (mode I in the frequency range VII)
This mode is similar to the general identification of the system Kremnij-2 (mode I in the frequency range III). It does not use cryptographic methods, so security must be ensured by code changes /3/. Furthermore, it seems that there is also a check code in this mode /11/. The mode is intended for jammed environments and when interrogated by many interrogating systems /3/. The interrogation is done with three pulses and a further pulse for side lobe suppression. Pulse diagram of the interrogation according to /3/:
The transponder can reply with 6 different codes. The response consists of two pulses, one on each of the response frequencies. The code is determined by the time interval T between the pulses and by the response frequency f B or f C on which the first pulse is sent /3/
On the screen, a target with identification is shown with a parallel bar /3/, /8/ Codes are different for aircraft and ships /11/.
Imitation Protected General Identification ("Guaranteed Identification") (mode II in the frequency range VII)
For a day, there are 9 11 possible interrogation codes available. From this large amount, a code is randomly selected and sent for an interrogation. The transponder must receive the code and select and send the matching response code from a set of 16 possible codes. The result is received by the interrogating station and verified. If the response code matches to the sent interrogation code, the target is considered as "own" /3/ Pulse diagram of the interrogation according to /3/:
The response consists of two pulses. The 16 possible response codes are formed by the time interval T between the two pulses (8 possibilities) and by the response frequency f B or f C on which the first pulse is sent (2 possibilities). /3/ Pulse diagram of the response according to /3/:
A target with guaranteed identification is displayed on the screen with a bar parallels with hook. /3/, /8/
Individual Identification (mode III in the frequency range VII), Distress and Alarm
According to /3/, the individual identification and distress are marked by a third pulse in the response signal. In contrast, /11/ is saying that the individual identification is defined by a three-digit code. A ground station can receive the distress signal as an alarm signal and display it with a lamp on the control panel, even if they do not make own interrogations /3/, /8/. The ground stations then have to scan their sector for the target /11/.
Overviews Frequency ranges: I 8600..9700 Mcs II 2520..3380 Mcs III 668 Mcs IV V VI 1532, 1458, 1470 VII Mcs
/1/ /1/ /1/, /2/. /8/
/2/
Modes Freq Mode Kremnij Parol Purpose
I/II+III I
x
III
I
x
x
III
III
x
x
VII
I
x
VII
II
x
VII
III
x
IV
x
V VI VII VIII
Interrogation
Response
12 response codes, distress signal 12 response codes or no Interrogation + interrogation General identification response on check code, of the check code distress signal Individual 2 kinds 3-digit code? /11/ identification 1 interrogation /3/, 6 response codes, distress General identification interrogation of the check signal /3/ code /11/ Imitation-protected 16 response codes, distress 911 interrogation codes /3/ general identification signal /3/ Individual 3-digit code identification Individual 5-digit code /11/ identification General identification 2 kinds
x
Altitude and remaining fuel
eBook IFF - Identification Friend of Foe in the Warsaw Pact
Document 1: Air Force •
Use of IFF systems
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Use of IFF ground systems
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Use of IFF aircraft systems
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Specifics of the use during radar jamming
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Distribution and use of IFF codes
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Security regulations
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Designation of the devices in unclassified correspondance Structure of code change tables
Document 2: Navy •
Radar IFF
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Hydroacoustical IFF
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Visual IFF
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Radio IFF
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In preparation, coming soon! Get your free preview!
Secrecy regulations when using IFF installations
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Accounting of IFF installations
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Storage of codes and filters and of IFF devices
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Scheduled preventive maintenance and repair
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Discarding IFF installations
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Dealing with the explosive devices of IFF systems Identification with civilian ships
+ Bonus Material Former secret documents in facsimile, with english translations
Sources Important: I visited all of the websites below. Two sites look a little bit questionable, so I'm not sure about security. Please use common sense when visiting unknown websites or retrieving material and follow basic rules: always use a fully patched and updated operating system, a patched browser (browser, plugins), defensive security settings, an updated virus scanner and never surf as administrator. And if in doubt, I prefer to use a live Linux system. /1/ http://www.radioscanner.ru/files/systems/file6947/ Description of SRO-2 und SRZO-2 in russian language, in djvu format /2/ http://forum.vardanank.org/ Наземный Радиолокационный Запросчик НРЗ-4П «Пароль»: Excerpt from training material for the NRZ-4P (russian language) Armenian forum, registration required. /3/ http://5ka.su/ref/war/0_object3060.htmls НАЗЕМНЫЙ РАДИОЛОКАЦИОННИЙ ЗАПРОСЧИК IЛ24: Study about the interrogation unit 1L24 (russian language) /4/ www.flugzeugforum.de Thread: Einsatz bei NVA-LSK, Freund Feind Kennung (german language) /5/ www.nva-forum.de Thread: Luftraumüberwachung, Nutzung Kennungsgeräte (german language) /6/ http://www.studfiles.ru/dir/cat20/subj241/file8670/view92366.html Шпоры по военке 4 курс VII семестр: Study which includes a description of the system Parol (russian language) /7/ www.radartutorial.eu Extensive website about radar systems, describes Parol systems and the general principles of side lobe suppression (german and english language) /8/ www.rwd-mb3.de Website about the missile and weapons service within the commander MB III of the East German forces; also includes descriptions of Kremnij and Parol systems (german language) /9/ http://nva-flieger.de/ffm.html IFF at NVA-Flieger.de (german language) /10/ DV 246/0/035 "Hydroakustische, visuelle, Funkmeß- und UKW-Freund-Feind-Kennung" (Volksmarine 1986) /11/ 1. Durchführungsanordnung vom 09.02.1990 zur Ordnung 010/9/022 - FunkmeßKennungsordnung (LSK/LV 1990) /12/ Eckard Schlenker, Ullrich Mattisseck: „Wer ist hier Freund, und wer ist Feind“ Fliegerrevue 10/92 (german language)
