I'm not saying this is rubbish, I mean we use this technique to obtain nice big encryption keys and so forth just like you say. What I'm thinking is that the things you are referring to there, like mouse positions, microphone input etc, must be deterministic or at least severely contained in nature
They are only deterministic if human behavior is deterministic.
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do you think an intelligent adversary could guess that I would press those keys on the keyboard? Even assuming that this only contains twenty bits of randomness, which is a very conservative estimate, 96f294735d4ee78d9327680498947e717166da6b03c1c48ff14ddc3d39b54468 would also contain 20 bits of randomness (in fact it probably contains 256 bits of randomness). However perhaps using this source of randomness would remove information theoretic security, I am not certain if the security would then fall to the hashing algorithm which has not been proven as information theoretic. I think I would still feel safe using the sha256 sum of the output produced by my random pounding on the keyboard as a one time pad key. Microphone input can actually be used to generate very secure random numbers, there are some 'true' RNG's which use microphone input to generate 'very high quality' random numbers, but honestly I would feel safe enough pounding on my keyboard for a five minutes and hashing the output with some secure digest.
and as such are in theory replicable by an intelligent enemy with vast resources e.g. my analogy of building an equation the size of a telephone directory to predict coin flipping. If you are able to determine a small enough frame (as in the right set of information as in the Frame Problem), and you know everything there is to know about X situation, then in theory you could produce a vast equation which perfectly predicts coin flipping and thus build a machine to do that job. I appreciate that by 'in theory', we could be practically talking light years or something, but still, this is a thought experiment.
An adversary who could guess the random keystrokes I just pressed could just as quickly guess a passphrase which is extremely likely to be much less random than that. So I highly doubt that such an adversary is at all realistic.
The reason why this could be important, is that you never know what mathematical breakthroughs could suddenly break our previous assumptions of "sufficiently random".
If we assume that the output I typed contains a single byte of randomness, and I type something 256 times as large prior to taking the sha256 sum of it, I will be extremely confident that unless sha256 is flawed the digest it outputs will be 256 bits of pure randomness. That is the neat thing about distillation of randomness, you can be extremely conservative. As long as the input contains 256 bits of randomness, the output will be 256 bits of randomness. If you assume that pounding on the keyboard for half an hour produces merely 256 bits of randomness (an extremely conservative estimate), then it is a conservative statement to claim that the resulting sha256 hash is a 256 bit random number.
Or... (time for conspiracy ohwow.jpg theory) it could simply be a case of a clever side channel attack in the far distant future when there is oddles of computational power to spare.
Side channel attacks generally avoid the requirement for oodles of computational power. Here is a side channel attack.
if password == input
puts "secret message!"
else
puts "fail!"
end
that (shitty) example is weak to a side channel attack because == short circuits. If the password is "cats" and the input is "cans" the compare will break on the n to t comparison, but if the input is dog and the password is cats then the compare will break on the d to c comparison. An attacker who can measure the amount of time it takes to puts "fail!" can thus determine how many characters of the password they guessed correctly. That is a cryptographic timing attack. Other side channel attacks include power analysis, noise analysis, etc.
So imagine a "secret chip" on every computer there is. It could work by replicating common algorithms standard software on the market uses to obtain large random numbers (literally all the time), and then storing these 'results' in a huge database on every single computer on the planet. This way every instance of a random number generated with whatever computer based input has been stored. I appreciate this is seriously far out and in fact may not be physically possible, but if you've studied the history of cryptanalysis in World War II, you'll know that governments *did* go to extraordinary extremes with respect to their era, albeit not that particular one. I mean if you told any German officer that the Enigma machine had been cracked years ago, he'd have laughed in your face, and probably continued laughing until the day after too, yet it was accomplished. Definitely easier just to key log and nick your passphrase though, lol.
And this secret chip has infinite storage capacity?
For those reading this thread (because kmfkewm probably has already heard about it), there IS a big controversy at the moment over the Huawai corporation (Chinese state company), because many western security people are saying they are putting surveillance systems onto their hardware. Which is a bitch because most of you will have some kind of Huawai equipment on your machines right now. Thing is... it would seem they have been learning those tricks from American corporations... The Economist had an entire magazine dedicated to this subject, so no, it is not science fiction that a State could go to these lengths.
Yes nations are always paranoid about using hardware from other nations.
The current stock market prices of shares, as in right now this very moment in time, are completely random in nature. This is not deterministic.
Neither is the result of me pounding on my keyboard. Also, the result of me pounding on my keyboard is secret, but the stock market is public, hence my dice example (which I ripped off from xkcd).
All the deterministic inputs become part of the price and so only entropy is left, meaning that stock prices will move at random at any given moment. Because of the profit motive, this is never not going to be true, but it is possible to discover information that turns previous 'random' data into a recognizable pattern (and thus make future prediction possible and consistent), but this is not possible here.
The stock market is public, so even if it is random it is a horrible source of entropy.
For contrast, it is almost certainly the case that the majority of people moving their mice about to increase entropy are doing so in similar ways. The space of possibilities might be very large, but that is not to imply people are using, or that their machines are using (e.g. read/writes to memory) the full search space. This is a passive way to obtain randomness, and it may turn out that in practice this is not a very good way of doing so. Perhaps once a person moves a mouse pointer from A to B, they approximately move it back from B to A or thereabouts. So there is predictability there and thus an opportunity for cryptanalysis (and if you think that's over the top, you haven't met any cryptanalysts, you think pine is paranoid, yeeeessh!).
I have absolutely no worry that the timing movement between my keystrokes + timing between mouse movements + direction of mouse movement + screen capture + key strokes + drive access times will not produce sufficient randomness. Especially since it can all be distilled, as the cryptographic hashing algorithms output contains the total amount of randomness present in all of its inputs (up to its output size) so even if each of the sources of randomness result in a few bits, and even if some produce no randomness at all, in the end it can gather up a huge input of all the different sources and then distill it down to its total randomness. Even if pounding on my keyboard produces only ten bits of randomness, I can just keep doing it and after a conservative amount of keystrokes have been gathered hash the total buffer of input and get my randomness as the cryptographic hash output.
I was thinking you (may) share private keys this way! You need to know the algorithm and send your email (using special software that sends at a very exact prearranged time). Then the other person has the timestamp for when the email was sent (not when it arrived, that wouldn't work), and they can use the algorithm to work out the current OTP decryption key in relation to current stock prices at that timestamp (or else I was imagining it to be like some exotic PGP, one key for encryption, that is useless for decryption, and visa versa, but I'm not sure how that would work across time), use it and read the information. This creates an incredibly tight window for an attack.
Need to know which algorithm? Also the attacker would just record the timestamp and check the stock market price at that time. And they would record the transfer of the algorithm as it takes place in the clear. Essentially you suggest that a OTP be based on the publicly viewable possibly-randomness of the stock market, at a precise moment in time that is sent in plaintext between communicating parties. That idea simply will not work. The randomness for the OTP is publicly viewable making it worthless, and your solution for key exchange is actually not a solution at all and consists of doing a plaintext key transfer.
See, you can do things like sampling the atmosphere and so on, but Alice and Bob aren't going to be able to both do that at the same time and come up with the same key without sharing. Sharing bad!
Didn't you just suggest that Alice and Bob share (via plaintext transfer) a moment to gather entropy from the (publicly viewable) stock market?
Anyway... I haven't worked it all out yet as you can see, this is a stupid child implementation, but if you thought about it for a whole year I bet you'd be able to come up with something close to bulletproof.
I doubt it.
Because people don't randomly type on keyboards when even they are trying, thus allowing cryptanalysis heuristics a break, but more pertinently, pine finds it difficult to leave well enough alone 
People don't need to type perfectly randomly, they just need to type randomly enough that the entirety of what they type has enough bits of entropy to fill up the output of the hashing algorithm. Conservative estimates put English at having about one bit of entropy per character. You could be ultra conservative and say every four characters have one bit of entropy. Then just type 1,024 characters worth of "random" English words and hash them together. Chances are high that the resulting output will contain 256 bits of entropy, if you use SHA 256 anyway.
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