5 ms·
you could try rowhammering yourself maybe? aren't the bitflips both spatially and temporally random, depending on em conditions? i never knew that any user co
by a-dub 5y ago
you could try rowhammering yourself maybe? aren't the bitflips both spatially and temporally random, depending on em conditions?
i never knew that any user could write into the entropy sources by writing to the random block devices... that's sketch.
- kardos 5y agoIf your hardware is impervious to rowhammer you'd get nothing
- RL_Quine 5y agoWhy is that sketchy? There’s nothing you could write that would make the output of the RNG worse.
- a-dub 5y agowell, i'm not a random number scientist or anything... but i do find it a little troubling that the random number generator at the core of linux that is trusted by everything has a secret "add more random" button on it.
- RL_Quine 5y agoIs it secret? You can just cat file.txt > /dev/random if you want to seed the generator.
- a-dub 5y agocan you? anyone in the village is allowed to dump old junk in there. old shoes, dead cats, kernel command lines, politician emails, old diaries and missing tax returns. and then what happens once it's in there? well, it can't really be trusted or used to actually seed the rng. half the junk in there is static. so it just kinda quietly gets mixed into the entropy hash pools... to what end exactly? it's neither ignored nor actually used in a meaningful way, so the whole problem it's trying to solve is ill-posed. this is a distinct code smell, where the problem was very hard and no good solution was found, so there are still remnants of tried and aborted approaches laying around like pieces of disused viaduct after a major earthquake. for something as critical as this, yes, i'd argue that it is indeed, sketchy. but that's less interesting than generating entropy by exploiting the digital systems equivalent of quantum effects. which has me wondering now: what if quantum entanglement is just rowhammer for reality...
- RL_Quine 5y agoNo matter what you send into the device, it can't make the output lower in quality, but it might make it better. Seems like a win-win in my books.
- a-dub 5y agoit's the notion, that it could make it "better", that is problematic. does this mean that users who don't feed the pool manually have inferior keys?
- rocqua 5y agoI think that rowhammering is too hardware specific. I could imagine much slower embedded devices being immune because their old slow RAM is too robust, and it would really suck if ECC RAM (perhaps even opaquely ECC RAM) causes your boot to hang.
- a-dub 5y agomaybe you could do something with race conditions? it's an interesting question: is there a clever way to extract random bits from a clocked ttl system by driving it in some weird way that is platform independent enough to cover the bases that don't already have hardware support for generating random bits (or have cycle counters)? i suppose the problem is that not all chips have a cycle counter so extracting clock drift/jitter isn't always feasible... i wonder what else could work... race conditions could be an interesting way to try to draw random bits, but probably very hardware dependent... i wonder if there are other glitchy things...
- account42 5y agoSome previous LWN discussions on this approach: https://lwn.net/Articles/642166/ https://lwn.net/Articles/642166/ https://lwn.net/Articles/802360/ https://lwn.net/Articles/802360/