6 ms·

Maybe they were hoping you'd join in order to fix them /s

seabass-labrax 3y ago
Unfortunately, there was apparently no such eagerness to improve the equipment. The officer who demonstrated the gadget to me did not seem at all concerned that his platoon had to have physical access to a radio in order to revoke its encryption key! One might like to think that the foe will be an officer and a gentleman, yet somehow I don't think they are going to publish those revocation certificates on the British Army's behalf should they manage to obtain one of our radios...!
- some_random 3y ago
  Wait how else would it be done? If you lose control of a radio you don't revoke the key you rotate it on all the radios you still control. The only reason you'd ever revoke a key is for administrative reasons (like you're handing the units off to someone else or something) in which case you'll have physical access just fine.
  - seabass-labrax 3y ago
    To be specific (as best I can; this conversation was about five years ago now), the radios used a form of symmetric encryption. The company would have squads of under ten soldiers, working covertly behind enemy lines in sabotage and reconnaissance. I don't remember whether the radios could communicate with each other only within the squads or across their entire platoon, but the thing that stood out to me was this: should a single soldier be captured (they'd be in enemy territory after all), each other soldier would have to meet together in person to reset the encryption keys. It's hard to believe, but if I understood the chap at the military exhibition correctly, the enemy could use a captured device to listen in to every communication among the squad/platoon, which would presumably make it perilous for them to reconvene again in secret - precisely what they would need to do in order to cycle the keys. If a more PKI-style mode of encryption was used instead, there could be a 'dead-man switch' or emergency button on the radio that would send a revocation certificate to all the other soldiers' radios if one was captured, causing the platoon to immediately cease encrypting their signals for the compromised set.
    - dmurray 3y ago
      Seems like a really hard problem though. A dead-man switch is likely to get triggered unintentionally if you're literally in a firefight. You could improve a bit with some kind of consensus protocol - "we all agree these six radios have not been compromised" - but coordinating that in practice seems hard, and vulnerable to an enemy capturing a single radio and initiating the consensus protocol.
      - some_random 3y ago
        In a tactical context, it's a huge ask to get intel value out of a radio in a timeframe that'll be useful. On top of that, compromised comms are almost certainly better than no comms. Military radio comms are pretty good (at least in the US), what I though OP was probably referring to was P25 which is a civilian protocol with several issues [1][2] [1]https://www.youtube.com/watch?v=re9nG81Vft8 https://www.youtube.com/watch?v=re9nG81Vft8 [2]https://www.youtube.com/watch?v=2se6th_6eYc https://www.youtube.com/watch?v=2se6th_6eYc (I was there for Matt's 2019 talk, haven't actually watched the 2024 one)
        seabass-labrax 3y ago
        Very interesting; thanks for the references. I'm no tactical radio expert, and can't quite remember, but I think the radio I'm referring to must have been the EZ-PRR[1], as that's the only similar-looking one that is reportedly in use by the British Army. > compromised comms are almost certainly better than no comms. Is this true when undercover though? As a layman, I would assume it is better for each soldier to attempt to find each other at first (like any other human beings, they'd have their 'Schelling points'), and failing that, attempt to get home safely on their own. The alternative - arranging a rendezvous over a potentially compromised comms method - could get them all killed or captured together. Is there a flaw in my reasoning? [1]: https://www.cryptomuseum.com/radio/selex/ezprr/index.htm https://www.cryptomuseum.com/radio/selex/ezprr/index.htm
    - livueta 3y ago
      Makes me wonder what exactly they were using and whether they may have just been using it wrong - even plain old p25 has otar: https://www.motorolasolutions.com/en_xa/products/two-way-radios-public-safety/astro-25-network/applications/over-air-rekeying.html https://www.motorolasolutions.com/en_xa/products/two-way-rad...
- dambi0 3y ago
  Perhaps you and the officer had different perspectives on the threat models under which revocation of radio encryption keys might happen? Maybe there are additional controls in place?

Unfortunately, there was apparently no such eagerness to improve the equipment. The officer who demonstrated the gadget to me did not seem at all concerned that his platoon had to have physical access to a radio in order to revoke its encryption key! One might like to think that the foe will be an officer and a gentleman, yet somehow I don't think they are going to publish those revocation certificates on the British Army's behalf should they manage to obtain one of our radios...!

some_random 3y ago
Wait how else would it be done? If you lose control of a radio you don't revoke the key you rotate it on all the radios you still control. The only reason you'd ever revoke a key is for administrative reasons (like you're handing the units off to someone else or something) in which case you'll have physical access just fine.
- seabass-labrax 3y ago
  To be specific (as best I can; this conversation was about five years ago now), the radios used a form of symmetric encryption. The company would have squads of under ten soldiers, working covertly behind enemy lines in sabotage and reconnaissance. I don't remember whether the radios could communicate with each other only within the squads or across their entire platoon, but the thing that stood out to me was this: should a single soldier be captured (they'd be in enemy territory after all), each other soldier would have to meet together in person to reset the encryption keys. It's hard to believe, but if I understood the chap at the military exhibition correctly, the enemy could use a captured device to listen in to every communication among the squad/platoon, which would presumably make it perilous for them to reconvene again in secret - precisely what they would need to do in order to cycle the keys. If a more PKI-style mode of encryption was used instead, there could be a 'dead-man switch' or emergency button on the radio that would send a revocation certificate to all the other soldiers' radios if one was captured, causing the platoon to immediately cease encrypting their signals for the compromised set.
  - dmurray 3y ago
    Seems like a really hard problem though. A dead-man switch is likely to get triggered unintentionally if you're literally in a firefight. You could improve a bit with some kind of consensus protocol - "we all agree these six radios have not been compromised" - but coordinating that in practice seems hard, and vulnerable to an enemy capturing a single radio and initiating the consensus protocol.
    - some_random 3y ago
      In a tactical context, it's a huge ask to get intel value out of a radio in a timeframe that'll be useful. On top of that, compromised comms are almost certainly better than no comms. Military radio comms are pretty good (at least in the US), what I though OP was probably referring to was P25 which is a civilian protocol with several issues [1][2] [1]https://www.youtube.com/watch?v=re9nG81Vft8 https://www.youtube.com/watch?v=re9nG81Vft8 [2]https://www.youtube.com/watch?v=2se6th_6eYc https://www.youtube.com/watch?v=2se6th_6eYc (I was there for Matt's 2019 talk, haven't actually watched the 2024 one)
      - seabass-labrax 3y ago
        Very interesting; thanks for the references. I'm no tactical radio expert, and can't quite remember, but I think the radio I'm referring to must have been the EZ-PRR[1], as that's the only similar-looking one that is reportedly in use by the British Army. > compromised comms are almost certainly better than no comms. Is this true when undercover though? As a layman, I would assume it is better for each soldier to attempt to find each other at first (like any other human beings, they'd have their 'Schelling points'), and failing that, attempt to get home safely on their own. The alternative - arranging a rendezvous over a potentially compromised comms method - could get them all killed or captured together. Is there a flaw in my reasoning? [1]: https://www.cryptomuseum.com/radio/selex/ezprr/index.htm https://www.cryptomuseum.com/radio/selex/ezprr/index.htm
  - livueta 3y ago
    Makes me wonder what exactly they were using and whether they may have just been using it wrong - even plain old p25 has otar: https://www.motorolasolutions.com/en_xa/products/two-way-radios-public-safety/astro-25-network/applications/over-air-rekeying.html https://www.motorolasolutions.com/en_xa/products/two-way-rad...
dambi0 3y ago
Perhaps you and the officer had different perspectives on the threat models under which revocation of radio encryption keys might happen? Maybe there are additional controls in place?