Ask HN: Is it possible to decrypt 256-bit encrypted radio in the battlefield? | Hacker News Reader

Ask HN: Is it possible to decrypt 256-bit encrypted radio in the battlefield?

26 pointskranke15521 comments

I'm part of a subreddit that reads defence reports and tries to keep up with "credible" news about the War in Ukraine. A newly released report by RUSI (The Royal United Services Institute, the world’s oldest defence and security think tank) says that Russians are now "near real time" decrypting 256-bit Motorola radio communications by Ukrainian forces. Here is the relevant passage.

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. (57)

They cite two interviews with Ukrainian military personnel and their own analysis of the system as a source:

57. Technical assessment of Torn-MDM conducted in Ukraine, June 2022

Some are saying this is impossible, that near real time decryption of 256-bit encryption is not possible.

I'm not an expert, so I'm punting over to the cryptographers here at HN. Could this be? Is it possible/feasible to do battlefield decryption of 256-bit radio encryption?

I don't know the particular model of the Motorola radio they are referring to.

Here is the report in question. Page 23 https://static.rusi.org/403-SR-Russian-Tactics-web-final.pdf

> Some are saying this is impossible, that near real time decryption of 256-bit encryption is not possible.

This is very possible -- provided the other side has the keys to decrypt.

Note that "decrypt" is different from "crack". All these radios would "decrypt" in real time (because the receiving radio has the decryption keys). Cracking (as in decrypting, when you do not yet have the key) should be impossible.

But perhaps there is some flaw in the implementation that allows for "decrypting" without needing the keys. Most encrypted systems fall not because the algorithm (the 256-bit part you talk about) itself is weak, but because some other aspect of the overall implementation has a flaw that allows one to obtain the "secrets" without attacking the encryption.

And... Keep in mind that this report, assuming it is credible, could be as simple as: "The other side has captured one of the radios and is using it to listen in on the comms".

Sorry for the offtopicness but could you please email me at hn@ycombinator.com? I want to send you a repost invite.

don't do it, pwg. opsec violation! :) ;p x

You can't crack a 256-bit key directly. But it's possible there is some mistake in the implementation, either leaking data or choosing keys badly. Or maybe there's just a mole.

One of my early mentors told me “encryption is easy, key management is hard”.

That’s pretty much the root issue. Just like with physical security, the devil’s in the details.

IDK what radios they're using in Ukraine. US military radios have devices that sync to one another that rotate keys. Also the radios hop frequencies every couple of minutes. I think it's pretty much impossible to crack without the "brain" device that is used to coordinate the radios, which is closely guarded.

IANAIA (...not an Intelligence Analyst), but on top of all the routine crypto failures (crummy "256-bit" crypto algorithm, or flawed implementation, or weak keys, or stolen keys, or ...), I can quickly think of:

- EM Side channels - if an ultra-sensitive antenna & receiver aimed at the Motorola radio can pick up any leaked signals from its internal electronics, then... This might only work on a small percentage of the units - due to a flawed production run at Motorola, or too-permissive QC standards, or poorly maintained kit, etc.

- Audio Intercepts - whether fancy parabolic mics, bugs hidden near Ukrainian forward observers, or the old "bounce the laser off the windowpane" trick.

- Concentrated Effort - the supercomputer and/or custom hardware needed to actually break the crypto may be far beyond what is viable for sustained, widespread use. But for either a PR boost, or if the Russians can convince the Ukrainians to cease use of their "easily broken" crypto...

- Cover Story - the Russians are obtaining the data without actually breaking the crypto...but certainly ain't stupid enough to talk about their actual methods.

What happens in the real world is that radios get captured and compromise the encryption.

This seems to be the most obvious reason.

I even saw a video of a Ukrainian drone picking up a radio with a hook

https://funker530.com/video/drone-steals-encrypted-russian-r...

Even capturing the radio is not enough. The crypto device that is used to synchronize the radios must be captured. The radios are synchronized in a secure area away from the battlefield.

"256-bit encryption" doesn't tell us anything. What's the algorithm? Where's the implementation?

AES-256 for example, is considered uncrackable. But it's perfectly possible that Motorola is using something wacky and home-grown and calls it "256-bit" just to get the bullet-point on the box.

Or an RSA private key of a mere 256 bits, which would be way too small. :-)

The standard in question (P25) is indeed using AES-256.

Not necessarily. It provides for all sorts of encryption schemes, including none.

That and they're likely LMR not P25 being in the part of Europe they're in.

AES is the only one supported with 256bit key length.

Most likely a key management/distribution scheme is used and that is what's been cracked. They obtain the key and then are able to decrypt the traffic as normal, no actual encryption is being cracked.

For those curious: /r/CredibleDefense/

It's a mix of some people who know what they're talking about, along with a bunch of people who don't know much, with the confidence that they know everything. Nonetheless, some good gems of intel pop up frequently in the comments.

Edit: my intent wasn't to put the subreddit down. It's a great resource and I peruse it a few times a week. Just be extra skeptical of claims you read (the CIA "agent" leak comes to mind).

It's better than looking at CNN tbh.

Or following updates in any other subreddits.

Most encryption even with fewer bits is not possible to hack in real time. What is often happening is some sort of cracking. It is not impossible that there are flaws in these devices. I know nothing about them. You simply do not brute force 256-bit encryption at least.

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