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Tick..Tick..Tick
I've recently bought a PRO-95 and am enjoying scanning.....
Several times now, while listening to our local police/sheriff channel, I'll run receive an unintelligible message. The voices are very high pitched, sounding like a cross between Minnie Mouse and Alvin the Chipmunk, and I know they're talking but I can't quite understand what they are saying. Superimposed over this is a loud ticking sound. What have I run into?? Wayne Port Townsend, WA |
Wayne Howell wrote:
I've recently bought a PRO-95 and am enjoying scanning..... Several times now, while listening to our local police/sheriff channel, I'll run receive an unintelligible message. The voices are very high pitched, sounding like a cross between Minnie Mouse and Alvin the Chipmunk, and I know they're talking but I can't quite understand what they are saying. Superimposed over this is a loud ticking sound. What have I run into?? Rolling code voice inversion, the "tick" is the sync telegram. Should be near to impossible to decode this, sorry. Transcrypt is a common manufaturer of such toys, also AFAIK Daxon. Wayne Port Townsend, WA regards - Ralph -- Want to get in touch? http://www.radio-link.net/whereisralph.txt |
Voice scrambling of the audio.
"Wayne Howell" wrote in message ... I've recently bought a PRO-95 and am enjoying scanning..... Several times now, while listening to our local police/sheriff channel, I'll run receive an unintelligible message. The voices are very high pitched, sounding like a cross between Minnie Mouse and Alvin the Chipmunk, and I know they're talking but I can't quite understand what they are saying. Superimposed over this is a loud ticking sound. What have I run into?? Wayne Port Townsend, WA |
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If it's voice inversion, even if the base freq shifts about, should be
pretty straight forward to decode. Any .wav (or whatever format) samples on the net available to download and examine? B. Ralph A. Schmid, DK5RAS wrote: Wayne Howell wrote: I've recently bought a PRO-95 and am enjoying scanning..... Several times now, while listening to our local police/sheriff channel, I'll run receive an unintelligible message. The voices are very high pitched, sounding like a cross between Minnie Mouse and Alvin the Chipmunk, and I know they're talking but I can't quite understand what they are saying. Superimposed over this is a loud ticking sound. What have I run into?? Rolling code voice inversion, the "tick" is the sync telegram. Should be near to impossible to decode this, sorry. Transcrypt is a common manufaturer of such toys, also AFAIK Daxon. Wayne Port Townsend, WA regards - Ralph |
bob wrote:
If it's voice inversion, even if the base freq shifts about, should be pretty straight forward to decode. Any .wav (or whatever format) samples on the net available to download and examine? How do you want to find out what inversion frequency is used at what moment? regards - Ralph -- Want to get in touch? http://www.radio-link.net/whereisralph.txt |
First you have to determine ow many 'base' frequencies are utilized.
it's likely a small number, likely 8, 16 at the most. If it's a variable scale, it could be a larger number, but again, not an impossible task. You will have to determine how the key is sent, or if it's a rolling sequence. (a rolling sequence would not require continuous sync pulses, so it's likely the receiver looks for the next key (base freq) and changes the mix frequency accordingly. To analyze it manually (to at least get some details about the transmission format) just grab a small (perhaps a few seconds) sample and tear it apart manually. Break it up with a computer sound editing program and play each slice repeatedly into a frequency inversion circuit (Ramsay sold one, there are also a few schematics floating about the net) until you recover natural sounding snippits of audio. Splice it all back together and see how it sounds. Document each mixer freq needed, and compare them to each 'tick' data byte. (you'll need a data slicer for this, again, see the net.) This will give you a good selection of raw data. Just to clairfy things, when I said "...it should be pretty straightfroward to decode." I was not suggesting it would not be labour intense. It could turn out to be a royal pain in the a$$, however, if it's simply inversion with a variable mixer freq, there's no real security there. It would be inconvienent to analyze, but again, the process is straightforward. To automate it will also take a lot of time, but again, unlike with digital ciphering, you're not up against large numbers and even larger permutations. Is there a sample of the audio somewhere on the net that could be downloaded? B. Ralph A. Schmid, DK5RAS wrote: bob wrote: If it's voice inversion, even if the base freq shifts about, should be pretty straight forward to decode. Any .wav (or whatever format) samples on the net available to download and examine? How do you want to find out what inversion frequency is used at what moment? regards - Ralph |
bob wrote:
roward to decode." I was not suggesting it would not be labour intense. It could turn out to be a royal pain in the a$$, however, if it's simply inversion with a variable mixer freq, there's no real security there. The problem may be that the tick usually has nothing to do with the number of frequency changes. The inversion frequency may change several hundred times per minute, and the tick is just used to keep in sync. regards - Ralph -- Want to get in touch? http://www.radio-link.net/whereisralph.txt |
Okay, so if it's several hundred times per minute, that would definitely
change everything. However, if that's the case, would it not be most likely they're employing some sort of sinewave (or sawtooth, or stepwave) 'seed' signal into a VCO which supplies the mixer freq? It's not impossible, but it may be unlikely the mixer freq changes that often. If it changes too much, then it itself starts to become a problem, because the switching itself will begin to encroach into the audio spectrum. The mathematical limit would be 3000 seed changes per minute, as this would impose a 50Hz noise on the information. I suppose part of the problem is my not ever hearing this type of signal, so I'm only able to imagine what it sounds like. Is the system is truly an analog mangling of the source material? Also, there was another system out back in the 70's where they took the passband, inverted it, sliced it up, and shifted the pieces about. It think Radio-Electronics did a feature on it, including a project for one that broke 300Hz-3000Hz into 4 pieces, mangled them a bit and out popped your encoded audio. It was a symmetrical system. The more I think about it, it could be a nasty chore to straighten it out. Harris has a system for HF that's straight analog but certainly not easy to decipher, but their's is not straight inversion either. If however, the mixer truly shifts about that much, it's simply not worth the effort, unless you don't mind placing your sanity at risk... :) Ralph A. Schmid, DK5RAS wrote: bob wrote: roward to decode." I was not suggesting it would not be labour intense. It could turn out to be a royal pain in the a$$, however, if it's simply inversion with a variable mixer freq, there's no real security there. The problem may be that the tick usually has nothing to do with the number of frequency changes. The inversion frequency may change several hundred times per minute, and the tick is just used to keep in sync. regards - Ralph |
The tick that started this thread is at a one second interval......
These scrambled (?) messages occur quite infrequently (perhaps 2-3 times a day) and it is always in incoming message. The dispatcher usually (but not always!) responds in plain talk. About half the time, from the context of the dispatcher's message, I can identify which field radio the scrambled (?) speech is coming from. And, in those cases I will have heard the same radio in clear speech and will hear it later on also. Wayne Howell Port Townsend, WA |
bob wrote:
Okay, so if it's several hundred times per minute, that would definitely change everything. However, if that's the case, would it not be most likely they're employing some sort of sinewave (or sawtooth, or stepwave) 'seed' signal into a VCO which supplies the mixer freq? Both seems to be in use, depending on the manufacturer. Check out those sites: www.transcrypt.com www.kavitsecure.com http://www.daxonfil.com/en/index.html It's not impossible, but it may be unlikely the mixer freq changes that often. It is not too unlikely - anything else would decrease the security too much. The more I think about it, it could be a nasty chore to straighten it out. Harris has a system for HF that's straight analog but certainly not easy to decipher, but their's is not straight inversion either. If however, the mixer truly shifts about that much, it's simply not worth the effort, unless you don't mind placing your sanity at risk... :) *g* regards - Ralph -- Want to get in touch? http://www.radio-link.net/whereisralph.txt |
Wayne Howell wrote:
The tick that started this thread is at a one second interval...... These scrambled (?) messages occur quite infrequently (perhaps 2-3 times a day) and it is always in incoming message. The dispatcher usually (but not always!) responds in plain talk. The same here with some APCO25 users :) Often only one person scrambles, the other not :-) About half the time, from the context of the dispatcher's message, I can identify which field radio the scrambled (?) speech is coming from. And, in those cases I will have heard the same radio in clear speech and will hear it later on also. Same here, too. Wayne Howell Port Townsend, WA regards - Ralph -- Want to get in touch? http://www.radio-link.net/whereisralph.txt |
the sync ticks give it away as hopping " rolling code voice inversion encryption " Rolling/Hopping Code Scrambling This inverts the audio around a frequency which keeps changing. This requires synchronization of the inversion frequency between sender and receivers. The security of this system depends on the combination of how often the inversion frequency changes and how random the change is. The use of random codes to specify the inversion frequency allows a high level of control over the security. This allows the techniques of key generation used in digital data security to be applied, yielding immensely large number of codes, and the added security from these changing frequently as well. " http://www.machine-ware.co.nz/Safehand.htm rather than " muse " yourself into oblivion , why not just type " rolling code voice inversion " into Google to learn why this is the " latest and greatest " form of super secure encryption , even used extensively by the military. you'd have more luck breaking into your cable box than decoding this newer encryption product ...... k................. On Thu, 09 Jun 2005 09:30:19 -0400, bob wrote: Okay, so if it's several hundred times per minute, that would definitely change everything. However, if that's the case, would it not be most likely they're employing some sort of sinewave (or sawtooth, or stepwave) 'seed' signal into a VCO which supplies the mixer freq? It's not impossible, but it may be unlikely the mixer freq changes that often. If it changes too much, then it itself starts to become a problem, because the switching itself will begin to encroach into the audio spectrum. The mathematical limit would be 3000 seed changes per minute, as this would impose a 50Hz noise on the information. I suppose part of the problem is my not ever hearing this type of signal, so I'm only able to imagine what it sounds like. Is the system is truly an analog mangling of the source material? Also, there was another system out back in the 70's where they took the passband, inverted it, sliced it up, and shifted the pieces about. It think Radio-Electronics did a feature on it, including a project for one that broke 300Hz-3000Hz into 4 pieces, mangled them a bit and out popped your encoded audio. It was a symmetrical system. The more I think about it, it could be a nasty chore to straighten it out. Harris has a system for HF that's straight analog but certainly not easy to decipher, but their's is not straight inversion either. If however, the mixer truly shifts about that much, it's simply not worth the effort, unless you don't mind placing your sanity at risk... :) Ralph A. Schmid, DK5RAS wrote: bob wrote: roward to decode." I was not suggesting it would not be labour intense. It could turn out to be a royal pain in the a$$, however, if it's simply inversion with a variable mixer freq, there's no real security there. The problem may be that the tick usually has nothing to do with the number of frequency changes. The inversion frequency may change several hundred times per minute, and the tick is just used to keep in sync. regards - Ralph |
Even back in high school the cable boxes were never a significant
problem... ;-) I will concur that a high rate rolling code inversion could be a complete pain in the keester, but I also maintain it would not be as secure as an asymmetrical digital system with an exception, that being key changes at a significant rate. If the rate of key changes equal the information rate, then you're flummoxed. If it's much less, then you have a good chance of figuring it out. Speech itself is simply the concatenation of known allophones that can only be serialized in limited and well known sequences, so the number of possibilities of inverted speech is limited. Digital encryption allows the absolute obscurity of the source information. Please don't read into this that cracking analog systems is a 'walk in the park' so to speak, but they are not nearly as secure as a digital system. I initially assumed the source signal was simple inverted speech with a key change once or twice a second; that would be easily deciphered. It would seem this is not at all the case with respect to the communiques being discussed. That said, there are some valuable cribs to be found in utility communications; call signs, phrases such as 10-4, roger, etc, are dead giveaways to someone on the right track, if indeed they are attacking something with a significantly lower rate of frequency shifts. B. krackula wrote: the sync ticks give it away as hopping " rolling code voice inversion encryption " Rolling/Hopping Code Scrambling This inverts the audio around a frequency which keeps changing. This requires synchronization of the inversion frequency between sender and receivers. The security of this system depends on the combination of how often the inversion frequency changes and how random the change is. The use of random codes to specify the inversion frequency allows a high level of control over the security. This allows the techniques of key generation used in digital data security to be applied, yielding immensely large number of codes, and the added security from these changing frequently as well. " http://www.machine-ware.co.nz/Safehand.htm rather than " muse " yourself into oblivion , why not just type " rolling code voice inversion " into Google to learn why this is the " latest and greatest " form of super secure encryption , even used extensively by the military. you'd have more luck breaking into your cable box than decoding this newer encryption product ...... k................. On Thu, 09 Jun 2005 09:30:19 -0400, bob wrote: Okay, so if it's several hundred times per minute, that would definitely change everything. However, if that's the case, would it not be most likely they're employing some sort of sinewave (or sawtooth, or stepwave) 'seed' signal into a VCO which supplies the mixer freq? It's not impossible, but it may be unlikely the mixer freq changes that often. If it changes too much, then it itself starts to become a problem, because the switching itself will begin to encroach into the audio spectrum. The mathematical limit would be 3000 seed changes per minute, as this would impose a 50Hz noise on the information. I suppose part of the problem is my not ever hearing this type of signal, so I'm only able to imagine what it sounds like. Is the system is truly an analog mangling of the source material? Also, there was another system out back in the 70's where they took the passband, inverted it, sliced it up, and shifted the pieces about. It think Radio-Electronics did a feature on it, including a project for one that broke 300Hz-3000Hz into 4 pieces, mangled them a bit and out popped your encoded audio. It was a symmetrical system. The more I think about it, it could be a nasty chore to straighten it out. Harris has a system for HF that's straight analog but certainly not easy to decipher, but their's is not straight inversion either. If however, the mixer truly shifts about that much, it's simply not worth the effort, unless you don't mind placing your sanity at risk... :) Ralph A. Schmid, DK5RAS wrote: bob wrote: roward to decode." I was not suggesting it would not be labour intense. It could turn out to be a royal pain in the a$$, however, if it's simply inversion with a variable mixer freq, there's no real security there. The problem may be that the tick usually has nothing to do with the number of frequency changes. The inversion frequency may change several hundred times per minute, and the tick is just used to keep in sync. regards - Ralph |
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