4 ms·
One thing you could do is to exchange the keys in a nonstandard way. Phone or whatever. Obviously still breakable but at least not by a standard dragnet.
by praptak 10y ago
One thing you could do is to exchange the keys in a nonstandard way. Phone or whatever. Obviously still breakable but at least not by a standard dragnet.
- andai 10y agoIf you're exchanging keys in person, I suggest looking into OTP, currently the only known mathematically unbreakable form of encryption, and so simple it has been used since at least World War I.
- acjohnson55 10y agoMathematically unbreakable if your pad is truly random
- chimeracoder 10y agoSure, but if your RNG is compromised, there's no point talking about encryption in the first place.
- srssays 10y agoThat's not really the case. OTP requires a large amount of perfectly unbiased randomness, implicitly from a hardware randomness source (otherwise what you have is more accurately a stream cipher). Contrast with deriving a key using cryptographic primitives, which can accept low-quality randomness (as long as there is sufficient entropy), that can be easily and transparently collected.
- klodolph 10y agoYes, in theory OTP requires perfectly uniform uncorrelated random input. However, in practice, you can use a randomness extractor… at which point, yes, we can't prove that someone with unbounded computational power wouldn't be able to crack it. But all known computational power is bounded.
- acjohnson55 10y agoRight. So now you have to figure out how to get a secure RNG into people's hands, so they can create pads. How does that work? Genuinely curious whether there's a reasonable solution.
- tialaramex 10y agoDevices that produce a trickle of truly random numbers can be produced for a few bucks. They're included in modern CPUs, for example. But that was never the problem. The problem is, now what? To use this OTP you need to securely deliver pads to everybody you'll ever send a message to. So, OTP is practical for a handful of secret agents who'll receive messages of a few dozen words per year from a single controller, and useless for most of us in the real world. _This_ problem is why we have public key cryptography.
- eru 10y agoSnarkily: a one time pad reduces the problem of exchanging secret messages to exchanging secret keys of the same length.. The only thing that OTP buys you is that you can exchange the pads at your convenience any time before.
- andai 10y agoYou only need to meet once. With a few GB (a couple bucks in a supermarket will buy a 8GB usb stick) you can communicate in text about 16 thousand books worth of words. In other words, to deplete the pad you would have to write sixteen thousand books. I think that's pretty convenient, as far as literally unbreakable encryption goes!
- eru 10y agoOh, definitely. The convenience of being able to secure your communication in advance is great. It's just that key-sharing is basically the most complicated and vulnerable part of modern cryptography.
- deleted 10y ago[deleted]
- shshhdhs 10y agoI wouldn't use the phone for exchanging plaintext keys. You're forgetting about ECHELON, wiretaps, and the dragnets where LEA are ignoring (or purposefully misinterpreting) the law. It's really cheap to store ALL phone calls these days, and just "playback" when you get the legal search warrant.
- jacquesm 10y agoAnd it doesn't count as surveillance until someone looks at it...
- praptak 10y agoIt's only about avoiding automatic dragnet, so making a person listen to the conversation and figure out the key counts as success.
- shshhdhs 10y agoAutomatic voice transcriptions has been a technology for greater than two decades.
- dredmorbius 10y agoExchange many keys.