ELINT / Signals Intelligence

[swaghauler]

Here's a good introduction to establishing a "listening post" using modern tech.

https://youtu.be/Nam87B2u6bo


Swag

[Homer]

Tactical COMINT is probably one of the few “technical” sources still available to commanders circa 2000. After all, in its simplest form it’s just a radio receiver with directional antenna and signal strength meter tied to a tape recorder or linguist. Encryption and decryption is probably through manual means. Therse should be a reasonable number of platforms (PRD-12 or TRQ-32 class) still available to conduct low end COMINT.

ELINT and operational/strategic COMINT is likely limited by availability of collection and processing resources as well as a decline in emitters. Ground based collection and processing sites have either become casualties (Elmendorf AFB and Fort Meade, for example) or suffered from security/resource disruption (I always figured NSA would reconstitute at Belvoir then move on to Buckley). Air and space assets, according to canon suffered from either outright loss or disruption to supporting infrastructure.

There will still be tactical ground based ELINT capable systems like the MEWSS or (maybe) Prophet/GBCS, but they will have lost much of their supporting analytic and maintenance structure. Although, they’re probably fully capable of classification and DF on surviving battlefield emitters like GSR, Counterfire Radar, or SHORAD emitters.

Assets such as the limited airborne platforms may be committed in support of major operations as a form of weighting. I could see Ancient Mariner getting support from remaining U-2/TR-1A, Rivet Joint, and Guardrail systems. Maritime assets will likely retain much of their onboard capability, with the cannon landings at Chah Bahar probably having some of the best EOB prep available.

SIGINT can be used to drive a plot, either indirectly as part of the info characters are given (Boomer) or directly (characters are assigned to escort an LLVI or SOT-A team, verify SIGINT derived data, or conduct a raid to recover or destroy sensitive equipment or personnel (SOI, cryptographer, etc).

[swaghauler]

Here comes another presentation on SIGINT...

https://youtu.be/iGdJCENreDY


Swag

[bobcat]

SIGINT is something i've put some thought into a lot recently. of course being the weirdo that actually deployed with a beigebox tucked away in my ruck i would say that wiretapping enemy field telephones can create some great adventure hooks. start with a mission to tap and tape enemy comms somewhere, and let the characters overhear something that they could act on immediately as a side quest or something.

[Homer]

I could see field phones getting a new lease on life in T2K for a few reasons. First, radios are going to be attrited by either wear and tear or action (more depending on how you use EMP effects). Second, specialized batteries and power packs are going to be scarce, with even the rechargeables becoming less effective over time- most field phones are either sound powered or work off commercially available batteries. Finally, no more KEYMAT is being generated, so wire offers a way to conduct secure, signature free comms without risk of intercept or DF unless the enemy has tapped your wire.

Anecdotally a friend of mine used to carry a lineman’s phone on FTXs as a way to communicate outside the radio nets. Including ordering pizza and arranging for drops of coke and cigarettes.

[Bestbrian]

Full disclosure: I was the HUMINT guy. :)

https://scontent-atl3-2.xx.fbcdn.net/v/t39.30808-6/304954800_10229673551489914_712131128082607077_n.j pg?stp=dst-jpg_p526x296&_nc_cat=111&ccb=1-7&_nc_sid=5cd70e&_nc_ohc=zNuyqrU_XDkAX8QeAtg&_nc_ht=scontent-atl3-2.xx&oh=00_AT95jw6gn2dbhqLGTr_MILiXjfszkM0KKOknSVRTOrI4 tQ&oe=631935BF

[swaghauler]

This first video talks about PORTABLE HAM Radio setups in the digital age. This video will be useful for a modern-day MERC campaign.

https://youtu.be/DGOyvNLk6Bg

This video talks about the "old school" SINGLE SIDE BAND HAM Radio that was developed to extend AM Radio transmission. The SSB is the mainstay radio of cruising sailors and would be common in the world of Twilight2000. It would be a major player in long-range (ie regional) comms. This video is so old, I'm asking you to rewind the cassette tape when you are finished watching it. :p

https://youtu.be/ivWmxFoTGDk

Swag

[bash]

I was thinking up some interesting things PCs might find find at or do with a listening post:


A tape deck with recordings of CW (Morse code) transmissions. There's boxes of tapes and they're dutifully labeled with dates. Most of the dates are months or years old but the most recent is from this week. Providing the PCs can understand Morse code the message lists times and dates followed by grid coordinates. Plotting on a map looks like starting positions. The current city is one of the targets and the target date is tomorrow.
The listening post has an HF radio setup and a notepad with several frequencies written down. If they monitor those frequencies they'll pick up a numbers station. With some good skill checks and a little GM guidance the PCs should find a Russian translation of Das Kapital on the shelf. Using the numbers as page/line/word number triplets spells out a message in Russian (GMs choice).
In Krakow (or some other free city) the post operator has tapped into phone lines that have been run across the city. The city's uses battery powered field phones to communicate with civil and military leaders in the city. Even the military commanders have been lax in their COMSEC and talk in the clear, obviously assuming no one in the city is able to tap the phone lines. A fun complication is a lightning strike burns out a switch box the listening post had tapped, the PCs notice their taps are dead and need to remove the taps before work crews discover them and trace them back to the post.

[Raellus]

Those are some cool ideas, Bash.

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[Homer]

Pretty cool ideas!

Great ways to introduce some adventure hooks. Or a one off mission in support of or to counter a listening post.

Does anyone have a mechanic for COMSEC and radio security? Like a roll against Electronics or INT to use an SOI or put up a directional antenna? Or breaking simple substitution cipher?

[bash]

Does anyone have a mechanic for COMSEC and radio security? Like a roll against Electronics or INT to use an SOI or put up a directional antenna? Or breaking simple substitution cipher?

For radio COMSEC I would probably go for the Electronics skill roll. A lot of military encryption devices are black boxes that connect to an otherwise unencrypted radio. Attaching them and loading keymat strikes me as more Electronics than Computers. The same holds for basic radio operations like setting up an antenna and such.

Breaking a cipher I would use the Computer skill rolled as an opposed check against the person doing the encryption.

While there's no specific rules for them, Merc2k has some radio electronics on the equipment list. They sort of just work so long as you have them and they're intact and do what they say on the tin.

[pmulcahy11b]

A lot of military encryption devices are black boxes that connect to an otherwise unencrypted radio. Attaching them and loading keymat strikes me as more Electronics than Computers. The same holds for basic radio operations like setting up an antenna and such.


As an RTO/other stuff in a DTAC, I could do all that, but I didn't have any Electronics skill. I would call doing the above an INT roll. You need to be smart, but otherwise anyone could be taught to do that.

Actually fixing those boxes? That's Electronics skill.

[bash]

As an RTO/other stuff in a DTAC, I could do all that, but I didn't have any Electronics skill. I would call doing the above an INT roll. You need to be smart, but otherwise anyone could be taught to do that.

Actually fixing those boxes? That's Electronics skill.

Awesome, thanks for that. My experience is with civilian radios so I've never been quite sure how to roll up the task. Most of the time I've just said a radio works or doesn't in a game and no task roll was needed.

I was actually a bit surprised looking at both Merc 2k and Dark Conspiracy and finding neither really have communications related skills enumerated either.

[Desert Mariner]

As an RTO/other stuff in a DTAC, I could do all that, but I didn't have any Electronics skill. I would call doing the above an INT roll. You need to be smart, but otherwise anyone could be taught to do that.

Actually fixing those boxes? That's Electronics skill.

Keep in mind that my experience is Air Force (Wing/Base level) based. For keying equipment, I agree that an INT roll would be the most appropriate. All you had to do was connect the cannon plug and press a couple of buttons. Generating the keys is a different story and would best be covered by a Computer (LINUX) skill.

[swaghauler]

Pretty cool ideas!

Great ways to introduce some adventure hooks. Or a one off mission in support of or to counter a listening post.

Does anyone have a mechanic for COMSEC and radio security? Like a roll against Electronics or INT to use an SOI or put up a directional antenna? Or breaking simple substitution cipher?

I do add a cascade of technical skills referred to as "Operator Skills." This cascade includes EW/ECM Operator, Radar Operator, Radio/Comms Operator, Sonar Operator, Millwright, Powerplant Operator, and Industrial Operator (including sewer plant, water plant, injection molding machines, extruding machines, and industrial ovens/food processors). I include Wire Tapping as a Qualification of my Radio/Comms Operator Skill (for those who are confused, I have posted my house rules in ANTENA's thread on Homebrew in this forum).
I give 1 exp in Radio/Comms Operator to all Military Basic Training Skill lists so every soldier has at least Familiarization (Skill 0 + Attributes) and all of the above Operator Skills use the average of for their Characteristic bonus. This Skill includes the use/setup of Field Telephones as well as Radios (hence the Comms part).

During play, I only require that a Skill roll be made if EW (electronic warfare for the uninitiated) is in play. Otherwise, no roll is needed AFTER Comms have been established!

Establishing Comms:

This involves running wire and plugging in phones to a switchboard or setting up an antenna and tying it into a radio. It is a ROUTINE Task and on an OUTSTANDING Success, your Radio's range will be increased by 5% to 30% (1D6 X 5) because of good antenna emplacement. A failed roll will see a Radio's range DECREASED by 5% to 30% (1D6 X5) due to poor antenna placement or a bad connection. A CATASTROPHIC FAILURE means the radio won't transmit or receive after being set up. Alternately, on an OUTSTANDING Success, the PCs may designate that the antenna is instead, placed so as to make detection more difficult. Large antennas normally use the Vehicle Spotting Chart in my Observation & Spotting Rules as they are tall and straight and need an unobstructed line of sight to the horizon. However, on an OUTSTANDING Success, the PCs can use the Spotting Chart for a Man-Sized target instead. The reduced Detection Range alone (1,000m) makes this a good choice for an Outstanding Success.
Once the radio or phones are running, no more rolls need to be made for basic Radio transmissions.

Advanced Commo Tasks: Direction Finding Of A Transmission.

If you have a [I]DIRECTIONAL ANTENNA, you may be able to determine the direction that a broadcast is coming from. This is an AVERAGE Task and requires that your directional antenna be able to be rotated in order to determine the direction of any transmissions. On an OUTSTANDING Success, the operator is also able to determine a rough RANGE in addition to a BEARING (direction) based on the received transmission's signal strength. It should be noted that this bearing is "cone-shaped" and can vary from as wide as 20% (10km on a 50km transmission) to as little as 5% (2.5km wide on the same 50km transmission) based on the quality of your Directional Antenna.

Advanced Commo Tasks: Triangulation.

If you have two or more radio operators with directional antennas in different physical locations, You may be able to TRIANGULATE a transmission. This is done by having each operator make a roll to Direction Find the transmission. This is an AVERAGE Task for two operators. Three Operators using Direction Finding from three differing points makes the Task ROUTINE and four Operators make the Task EASY. The transmission will be isolated to a "box" a number of kilometers square equal to 20% of its Range for two operators (ie a transmission at 50km will be located in a 10km box). The box size will be 10% of the Range for three Triangulators, and just 5% for four or more Triangulators. On an OUTSTANDING Success, Altitude will also be established for the transmitter (please note this will be the altitude of the ANTENNA, not the radio).

Decryption OF Transmissions:

This will require specialized computer gear and the difficulty will depend on the quality of your equipment and the type of encryption.

Scrambled Encryption: This simply involves rearranging the letters in words. It is the easiest method to break because you only need a key/guide.
It is a DIFFICULT test to decrypt.

Scrambled & Frequency Hopping: This system "skips" from frequency to frequency and can be very hard to decrypt because you must also determine the sequence of the frequency hopping before you can begin. Frequency Hopping alone is not completely useful (AVERAGE Task to decrypt) because a lot of modern radios can listen in on multiple transmissions (frequencies) at once. Thus recognizing the pattern is pretty straightforward. HOWEVER, with this method, not only do you have to record the pattern of frequencies, but the words are also scrambled and will have to be put back in order. Thus, this Encryption is a FORMIDABLE Task to break.

Digital Encryption: The holy grail of Encryption when it became common in NATOS "LINK" data-sharing systems (LINK 12 was the most common in the 90s). It uses "bits" or characters to represent EACH WORD or even LETTER in a communication. The initial systems used 4-bit, 6-bit, and 8-bit (the most common in the Cold War era) representations for each LETTER in the LINK system. This meant that a 100-letter phrase would need 800 characters to be decrypted and placed in a proper order to read that phrase. Modern systems now use 128-bit encryption PER LETTER! Thus you will need a computer and special software that can do MILLIONS of operations per second to decrypt Digital Encryption. Therefore this is an IMPOSSIBLE Task to perform.

That is just an overview of my Radio Ops/Comms rules. I hope that helps.

Swag.

[Homer]

Thanks, that’s great stuff. I like that comms have to be established- it’s a 10 level common task, but Murphy can always intervene.

Expanding on the operator tasks idea, I’d offer at a few additions:

Trouble shooting: anything from splicing a break in wire to field repair of an antenna. EASY for something like tracing commo wire or finding a loose ground strap; AVG for a splice or retiming a net with a freq hop master; DIFFICULT for a field expedient repair to a vehicle or man pack antenna or diagnosing a bad power amp; IMPOSSIBLE for diagnosing circuit issues without test set, etc

Communications field craft(?): antenna savvy, radio positioning, battery conservation, etc. EASY for preserving batteries in extreme cold/hot/wet environments (one time role), avoid EMP effects; AVG for constructing field expedient antennas (jungle 292 type) or for customizing radio equipment (Wire antenna woven through molle links instead of using a whip to keep a low profile; tie 550 cord to OE254 head and throw over tree rather than use poles, etc), cut antenna for AM radio; establish a retrans network; DIFFICULT construct a directional FEA (vertical half rhomboid), site antenna to to minimize intercept/DF probability; IMPOSSIBLE cannibalize components for field expedient repair of internals, etc.


Just a few thoughts.

[pmulcahy11b]

Generating the keys is a different story and would best be covered by a Computer (LINUX) skill.

That's true; I have no idea how hopsets/locksets are generated except that they are done at G2 COMSEC and disseminated by radio. (I do know how to disseminate a set -- another no skill skill.)

It seems that if you could intercept one of those disseminations you'd be a long way towards breaking into an enemy net.

[Homer]

I can help a little, pardon the tech speak and my not dealing with this stuff in detail since the 90s!

For US units, keymat originates at NSA. They have executive responsibility for COMSEC in the US.

The SINCGARS (single channel ground air radio system) was becoming the default
FM radio system for US ground forces replacing the older PRC/VRC series radios and associated KY-57 COMSEC modules with a single unitized radio. The new radio was designed to operate in frequency hop/cypher text mode using time based hopsets and keymat based crypto. It was interoperable with other radios by selectively disabling either freq hop (usually), crypto(rarely), or both (single channel plain text). There was an USAF version of SINCGARs, but to my knowledge it didn’t field until the 2000s.

In the 90’s encrypted keymat was distributed by secure courier where it was uploaded into a key management system computer, decrypted, and prepared for loading into master AN/CYZ-10 (ANCDs). The master ANCD is then couriered to the user unit and used to fill the remainder of the unit’s ANCDs, which fill SINCGARs, VINSON, etc. ANCDs were down to the company and even platoon level in some units, but never went forward of the assembly area. This would likely be the system in effect during the early phases of the Twilight War for most force package one units.

Before the transition to digital key management, keymat was generated on magnetic storage media (hard disks or magnetic tape), which was couriered to theater level signal units where it was produced on punched paper tape. Once there the punched tape was fed into a KOI-18 tape reader and used to fill either ANCDs (at the end of this method) or the older KYK-13 fill device. As with the ANCDs these were them couriered and used to fill the unit’s equipment. This would still be common in many units, and could be adopted by FP1 units when their commercial spec KMS computers succumbed to combat. Unlike the ANCD KYK-13s didn’t include time, so that would have to manually loaded. KYK-13s were commonly used to fill VHF radios in army aviation units even after the ANCD came into use since the HAVE QUICK utilized a different freq hop technology than SINCGARS.

The ANCD was a common fill device that could hold both hopsets and encryption keys as well as fill a number of different devices. In addition the ANCD could be loaded with information for multiple units, challenge/password data, and SOI data.

Both the SINCGARS and HAVE QUICK systems allow for Over The Air Rekey (OTAR- loading a new crypto key) and ECCM Remote Fill (ERF- loading a new hopset). This is an alternative to manual courier, but as Paul said it’s less secure. That said, you’d have to have the MAN frequency, a compatible radio, and be in range. Maybe a surviving NSA reconstitutes at Buckley ANGB, CO and begins disseminating keymat by courier and OTAR to high priority units or operations and SOI for everybody else.

With non freq hop radios, the COMSEC process is similar using either a KYK-13 or OTAR to fill the VINSON. Units using freq hop radios must operate in single channel mode when working with non freq hop units. An example is a SINCGARS equipped US unit working with a Clansman (non FH) equipped UK unit. This was also the case when a SINCGARS equipped unit was working with dismounted forces using the PRC-126 squad/team radio which did not FH- a SINCGARs somewhere in the remainder formation had to be on SC mode to talk to the 126s or the dismounts carried a FH SINCGARs to talk FH back to the vehicles. Still better than the Motorola saber which had its own encryption and didn’t talk to anything else. All that changed when the MBITR started to appear in the late 90s, but they’d be hen’s teeth in T2K and probably confined to SMUs.

Anecdotally, most OTAR and ERF is done within small units in locations like assembly areas where the radios SHOULD be in low power. Sometimes there’s a little yelling and choice words involved, especially when dealing with loading time!

[bash]

The initial systems used 4-bit, 6-bit, and 8-bit (the most common in the Cold War era) representations for each LETTER in the LINK system. This meant that a 100-letter phrase would need 800 characters to be decrypted and placed in a proper order to read that phrase. Modern systems now use 128-bit encryption PER LETTER!

This is not quite accurate. A bit means "binary digit". Each bit can represent two states, on or off (1 or 0). A 100 letter phrases encoded as bytes (8 bits per byte) will weigh in at 800 bits, not characters.

Encryption like SAVILLE used is what's called a stream cipher. With a stream cipher a key fed into an algorithm to generate what's called a "key stream". Every bit of input data is combined with a bit of the key stream, usually with an exclusive-OR operation, to get an enciphered bit. A key stream essentially looks like random noise, least it should look like noise, and so long as you feed the same key into that algorithm if you feed in the enciphered bit you'll get the plaintext bit back out.

The size of the key is really describing the periodicity of the key stream. If the key was small, say only 8 bits, you could easily generate all the key streams from every possible key since there's only 256. Assuming your encryption algorithm doesn't have some other mathematical, process, or equipment weakness your key size increases the difficulty of someone trying every possible key. At 128 bits there's more possible keys that atoms in the universe IIRC. So it's not every letter being encoded with 128 bits but some pseudorandom extremely long pattern generated by the 128 bit key.


Thus you will need a computer and special software that can do MILLIONS of operations per second to decrypt Digital Encryption. Therefore this is an IMPOSSIBLE Task to perform.


If a message is digitally encrypted I would put the difficulty as literally impossible. Unless there's some sort of key a character can get ahold of there's no practical way to crack the encryption. For military gear that means having the encrypted signals and having an intact key loading device and the appropriate encryption equipment. Without all that you'd need a billion years to find the encryption key.

[swaghauler]

This is not quite accurate. A bit means "binary digit". Each bit can represent two states, on or off (1 or 0). A 100 letter phrases encoded as bytes (8 bits per byte) will weigh in at 800 bits, not characters.

Encryption like SAVILLE used is what's called a stream cipher. With a stream cipher a key fed into an algorithm to generate what's called a "key stream". Every bit of input data is combined with a bit of the key stream, usually with an exclusive-OR operation, to get an enciphered bit. A key stream essentially looks like random noise, least it should look like noise, and so long as you feed the same key into that algorithm if you feed in the enciphered bit you'll get the plaintext bit back out.

The size of the key is really describing the periodicity of the key stream. If the key was small, say only 8 bits, you could easily generate all the key streams from every possible key since there's only 256. Assuming your encryption algorithm doesn't have some other mathematical, process, or equipment weakness your key size increases the difficulty of someone trying every possible key. At 128 bits there's more possible keys that atoms in the universe IIRC. So it's not every letter being encoded with 128 bits but some pseudorandom extremely long pattern generated by the 128 bit key.



If a message is digitally encrypted I would put the difficulty as literally impossible. Unless there's some sort of key a character can get ahold of there's no practical way to crack the encryption. For military gear that means having the encrypted signals and having an intact key loading device and the appropriate encryption equipment. Without all that you'd need a billion years to find the encryption key.

You undoubtedly have more experience than I do, so I'll take your word for it.

I too require PCs to have a powerful computer with specialized decryption software to have an IMPOSSIBLE chance to break digital encryption. I note that in my previous post.

[bash]

You undoubtedly have more experience than I do, so I'll take your word for it.

I too require PCs to have a powerful computer with specialized decryption software to have an IMPOSSIBLE chance to break digital encryption. I note that in my previous post.

A meant literally impossible as in can't accomplish rather than simply Impossible skill check difficulty.

[pmulcahy11b]

A meant literally impossible as in can't accomplish rather than simply Impossible skill check difficulty.

I have difficulty believing that. One thing we've all learned in the modern computing age is that anything can be hacked.

[bash]

I have difficulty believing that. One thing we've all learned in the modern computing age is that anything can be hacked.

Hacked is a highly qualified statement. There's lots of components of communication systems that can be "hacked". Some parts are much easier than others, the encryption systems tends to sit more on the computationally infeasible end of the spectrum. Most successful hacks are more on the user side of a system like brute force guessing poorly generated/reused encryption keys.

So I'm definitely not saying systems are unhackable, it's just the PCs aren't going to be able to "hack" encrypted comms with a pre-TDM laptop they might have with them. Even if they were hauling around a supercomputer they couldn't expect to brute force any military encryption.

[Homer]

I think comms using reprogrammable encryption are going to be infrequent almost three years post tdm. It’d be easier to produce a paper SOI that gets couriered out and changed on a schedule than go to That’s essentially an encryption guide or code book (brevity codes) similar to JN25 or Admiralty Code. With time, an SOI or code can be compromised, mainly due to induced human error or capture. That countermeasure to that is introducing a new edition frequently. Couriers could see more use, with light aircraft and the remaining helicopters falling back into a liaison and courier role.

That will be another challenge for PCs as they re-enter friendly lines without current challenge/password or recognition signals, or counter “friendlies” with different signals. There’s adventure seeds to capture an SOI or codebook, interdict a courier, or protect the same. High priority missions may see PCs issued with encrypted comms gear and COMSEC equipment (ANCD, KYK, etc).

[Desert Mariner]

Hacked is a highly qualified statement. There's lots of components of communication systems that can be "hacked". Some parts are much easier than others, the encryption systems tends to sit more on the computationally infeasible end of the spectrum. Most successful hacks are more on the user side of a system like brute force guessing poorly generated/reused encryption keys.

So I'm definitely not saying systems are unhackable, it's just the PCs aren't going to be able to "hack" encrypted comms with a pre-TDM laptop they might have with them. Even if they were hauling around a supercomputer they couldn't expect to brute force any military encryption.

Some examples of the use of brute force, from RSA Labs Encryption Challenges, using distributed networks, not a stand-alone machine.

• 56-bit cracked in 250 days by 16,738 total participants
• 64-bit cracked in 1757 days (4.8 years) by 327,856 participants
• 72-bit remains uncracked after 7,241 days (19.8 years) and 143,497 participants (projected time remaining 27,828 days (76+ years))

To me, the question isn’t, Can you crack the encryption?, but Is it worth doing so? In the case of the above 72-bit key, even if you manage to crack it, does a single decrypt (or even a whole day’s worth of decrypts) provide any usable intelligence decades after the fact?

[bobcat]

for more modern setting two pieces of SIGINT gear i love to implement in more modern settings. the Wifi Pineapple and the Dope Scope. they balance each other out because the wifi pineapple is mostly intended for infiltrating networks (it can also be used as a wifi extender), and the dopescope is built to find anything emitting wifi signals. granted your range may vary and most the time i just put both at 50M and then adjust it based on terrain.

of course even without purpose built systems, with access to cheap SDR's, beer cans, and duct tape you can put together some surprisingly effecting radio direction finding equipment. might not be ideal for cracking crypto but you can do surprising things with very little.

[Spartan-117]

That’s essentially an encryption guide or code book (brevity codes) similar to JN25 or Admiralty Code.

Speaking of brevity codes:

ZBM2

;)

[Homer]

speaking of brevity codes:

Zbm2

;)

zbk1!

[Spartan-117]

zbk1!

Ah, Z and Q codes. Brings back fond memories of hitting the books at NCS WTC long years ago. I have not missed using them though.

[bash]

Some examples of the use of brute force, from RSA Labs Encryption Challenges, using distributed networks, not a stand-alone machine.

• 56-bit cracked in 250 days by 16,738 total participants
• 64-bit cracked in 1757 days (4.8 years) by 327,856 participants
• 72-bit remains uncracked after 7,241 days (19.8 years) and 143,497 participants (projected time remaining 27,828 days (76+ years))

To me, the question isn’t, Can you crack the encryption?, but Is it worth doing so? In the case of the above 72-bit key, even if you manage to crack it, does a single decrypt (or even a whole day’s worth of decrypts) provide any usable intelligence decades after the fact?

Note that the SAVILLE system uses a 120-bit key. It would take trillions of years to brute force a single key if you could build a system that tried a quadrillion keys per second. So the time taken to recover a single key with a brute force search (even with mathematical principals like the Birthday Paradox) is directly related to a functionality of decryption. If a single key takes a trillion years to recover the practicality of the system is effectively zero.

[Raellus]

Do radio direction finders only "work" (i.e. locate the signal) when a radio is transmitting? If a radio is just turned on, can RDF equipment locate it?

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[chico20854]

Do radio direction finders only "work" (i.e. locate the signal) when a radio is transmitting? If a radio is just turned on, can RDF equipment locate it?

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I think it depends on the system... I recall that each node in the Mobile Subscriber Equipment (MSE) division-level cell network, which was state of the art in the 80s and fielded US Army-wide in the mid-90s, transmitted at all times. When I was in a divisional signal battalion the officers seemed disconcertingly nonchalant about the EW vulnerability that presented - a captain explained to me that since there were so many transmitting in a division area the enemy wouldn't know which one to shoot at, unsure whether they were hitting the division CP or a battalion rear support HQ.

For a more conventional radio, I think it's more complicated/harder. I'm not sure if there's some sort of RF frequency energy given off by the electronics that a sensitive receiver can pick up. (The KGB/GRU supposedly had monitoring equipment that could detect and record the internal signals in electric typewriters, parking trucks with antennas outside NATO installations, so it's possible).

[Homer]

Generally speaking, only transmitting sets are locatable with military type gear. That’s one reason you’re taught to keep transmissions short, use terrain masking, minimize power and in some circumstances to move after talking if you can.

There are two exceptions-

Theoretically, a very precise directional antenna, signal strength meter/spectrum analyzer, and a vehicle powered or generator powered superheterodyne receiver can always find the receiver by localizing the drop in signal strength and the emissions of the receiver’s local oscillator as the carrier wave is separated out, but for practical purposes this is limited to close detection distances with a receiver due to the low power involved. (Holding two radios close while transmitting on a third can generate oscillator interference.) This is similar in principle to the technology used by radar detector detectors or by the tv tax van in the UK.

Equipment that maintains a low power data “handshake” with a network like cellular phones, Mobile Subscriber, and high power cordless are vulnerable to location of the affiliation signal by specialized equipment. As these operate outside the standard military bands, this equipment may be less common by 2000. Some of the countermeasures to this type of location are frequency agility, power management, and location/use of signal attenuation camouflage (corrugated metal works great).

That said, powering off saves batteries. I could see radio transmission schedules coming back into play as batteries become short. The original rechargeable whuch would have been around at the time weren’t a great piece of kit.

[bash]

Do radio direction finders only "work" (i.e. locate the signal) when a radio is transmitting? If a radio is just turned on, can RDF equipment locate it?

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A heterodyne receiver has a local oscillator running at the frequency you're listening on. The radio compares this local frequency with a received signal to pull out the intermediate frequency, the signal that was transmitted. While the local oscillator isn't necessarily transmitting anything itself, wires/leads in the radio can end up broadcasting this beat frequency or a harmonic of it. Since those wired aren't a tuned antenna it won't be a strong signal and can be blocked by the body of the radio it's definitely possible for a sensitive detector to pick up such leakage.

For a military radio with their nice rugged metallic cases picking up these spurious signals would be pretty difficult and only effective at relatively short ranges. A damaged or scratch built radio would be easier to detect and at slightly better ranges.

Another possibility, even on unpowered equipment is detecting the P-N junctions of semiconductors. You broadcast a particular frequency (depending on the size of the junction) and listen for a harmonic response. Again this is not necessarily easy because it's an untuned antenna and the inducted power is minuscule. It requires a specially built detector and relatively close range. Good metallic cases with proper wiring/grounding will block most such signals. Many "bug detectors" work on this principal.

Passive "foxhole" radios don't have local oscillators and can't be detected when they're receiving. But besides that it's definitely a possibility if the PCs (or OPFOR) has good SIGINT gear and trained operators.

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This is similar in principle to the technology used by radar detector detectors or by the tv tax van in the UK.

I believe the TV tax vans only ever used detectors that would pick up the spurious broadcasts from the TV's CRT or BFO. The earliest detectors picked up signals from a TV's horizontal scanning circuit (well a harmonic of it) while later vans listened to the BFOs of the VHF and UHF detectors. They had highly directional antenna arrays on the top of the van and using a registered turret could take a bearings on detected signals. With two bearings they could triangulate the house with a TV and comparebig to their list of paid and expired TV licenses.