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Thread: The public use of ENCRYPTION

  1. #76
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    Quote Originally Posted by Mars View Post
    Further to your comment...

    Rekeying often, doesn't mean use a multikey radio and manually change the key via the soft menu, every week. Rekey means physically load new key(s) into radio at specified interval or when commencing a new project/investigation. This practice mitigates many keys/ops being compromised if a radio itself is stolen/compromised.

    Load 100 multikeys into a radio. Switch the key every week. But if an adversary has obtained a radio and dumped all 100 keys, they'll be listening each time the key is soft-changed. Multi-key should only be used for traffic segmentation/unique-per-agency.
    A well funded adversary (TLA Agencies) would not even have to go to the hassle of getting those 100 keys out of a recovered radio.

    Say for example they recorded all of the traffic for months directly at baseband using SDR, they could replay all those messages later into a signal generator and use the recovered radio to do all of the decoding for them. "Data is a toxic asset" (Schneier). Get rid of those keys as soon as you are done with them. Don't even write them down.


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  3. #77
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    This is why I'm a fan of the ASTRO25 KMF/OTAR scheme. A radio gets compromised, you can remotely inhibit/zeroize it, then generate a new TEK and push OTAR to the rest of the network (emergency rekey.) Of course the whole system falls apart if your users don't properly account for and report missing radios. Accountability is critical. Once a key is no longer in use, destroy any remaining copies of it. Generally you only want to keep one future key preloaded on radios to enable a smooth changeover, but if any radios get compromised, perform an emergency rekey on all radios on the network; generate brand new keys and burn the old ones.

  4. #78
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    The best method still is to not use a communications device at all. Face to face still works.
    Apparently NOT a radio professional.

  5. #79
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    Quote Originally Posted by com501 View Post
    The best method still is to not use a communications device at all. Face to face still works.
    Even then, there's filthy people who like wearing wires, trying to make a crime out of something that isn't, or entrap someone into doing something they normally wouldn't do. The world is full of....people. The human is not going to last much longer, in the multi-billion-year-old story that is Earth.

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  7. #80
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    Quote Originally Posted by com501 View Post
    The best method still is to not use a communications device at all. Face to face still works.
    One time Pads, dead drops, numbers stations. Time tested!

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    The tamper switches has failed often in the MTS2000 series causing the radio to lose the key, we had to bypass that feature.

  10. #82
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    Quote Originally Posted by PSYKO_Inc View Post
    =Of course the whole system falls apart if your users don't properly account for and report missing radios. Accountability is critical.
    We run into this in the public safety infosec field all the time. The best way to guarantee this is to provide a kind of immunity, IE: You won't get in trouble if you report the loss immediately so steps can be taken.

    The majority of delays in reporting lost radios (lost badges (lost tasers (lost guns (etc)))) is fear of repercussion. Obviously if you have the same nitwit every week losing a radio that's one thing, but I'd rather have someone report the loss immediately so it can be mitigated than wait until they "retrace their steps".

    Slightly off topic, just something I'm dealing with a bit at work.

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  12. #83
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    One time pads are the absolute best there is. Book codes are good too. Both have traditionally been used with number stations and the like. One advantage of book codes is they are lower profile. Hard to explain why you have a sheaf of flash paper with small columns of numbers on them.