On real-time decryption of encrypted radio communications

Rodrigo de Azevedo

7/30/24, 4:10 PM

According to Jack Watling & Nick Reynolds,

Ukrainian officers recalled one incident in which the Russian headquarters gave pre-emptive warning to its units of an artillery strike based on Ukrainian troops calling in a fire mission. The Ukrainian troops were communicating with Motorola radios with 256-bit encryption, but it appeared that the Russians were able to capture and decrypt these transmissions in near real time. The most likely system for such functions is the Torn-MDM.

_{Source: Jack Watling, Nick Reynolds, Meatgrinder: Russian tactics in the second year of its invasion of Ukraine, Royal United Services Institute, 19 May 2023.}

This claim is discussed on Hacker News, where it is claimed that the aforementioned radios are Project 25 (P25) radios using 256-bit AES.

Since I find it hard to believe that anyone can decrypt 256-bit AES in "near real time", I assume that – excluding the possibility that old-fashioned HUMINT is to blame — some design or implementation weaknesses are being exploited. Perhaps some of these weaknesses have been published in academic (rather than military) publications. References would be most welcome.

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Morrolan

7/30/24, 4:41 PM

Doesn't really answer what you asked for, so I'll put it here: There is, of course, the real possibility that one of the communicating parties just happened to be sending in plaintext. A rather famous problem of many P25-compatible radios, which seems to happen more frequently than one would be inclined to believe - see e.g. this talk by Matt Blaze: https://www.youtube.com/watch?v=7awwG9aaR4c

Maarten Bodewes

7/30/24, 9:25 PM

There are many possibilities here; brute forcing AES is obviously not one of them. AES being cracked is very unlikely as well. The most simple one is human intelligence; having the key or a captured listening device would be much more obvious. Then there are side channels (frequency analysis), bad implementations and whatnot to worry about.

Elon Musk

I sit in a Tesla and translated this thread with Ai:

EN: On real-time decryption of encrypted radio communications

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