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sfb30

What government attack vectors against Bitcoin do you deem most likely to work?

From Wikipedia:

In order to prevent double-spending, the network implements some kind of a distributed time server, using the idea of chained proofs of work. Therefore, the whole history of transactions has to be stored inside the database, and in order to reduce the size of this storage, a Merkle tree is used.

So I would transact the heck out of it and make the database huge. IIRC at the moment every user needs a full copy of the database of every transaction, so if the .gov can make a multi-terabyte database a requirement, that would knock it on the head quite hard.

Also, the last time I glanced at the source code it looked quite ropey, and that makes me think it will have lots of exploitable parts lurking for the right skilled people to find and attack.

Reply
Clippy20

Do users need to store the Merkle tree only, or the full database? If they only need to store the Merkle tree, then could the network proportionally counteract the effect of this database lengthening by increasing the datablock length? Does use of a Merkel tree reduce the fraction of the database that each user needs to store?

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See in context
by Kevin
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21

Now you can donate to Singularity Institute using Bitcoin.

Currently Bitcoin mining appears to be profitable as only bubble economics can be. Already some Less Wrong users have purchased GPUs and started mining Bitcoin. Please consider sending some Bitcoins to SI at address 1HUrNJfVFwQkbuMXwiPxSQcpyr3ktn1wc9

2014 Edit: Please donate Bitcoin by using the Bitpay link on MIRI's donate page. Thanks!

.

 

Personal Blog

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Singularity Institute now accepts donations via Bitcoin
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[-]imaxwell80

If you want to donate to SIAI, I have an offer that will probably allow you to donate more!

My Radeon 5970 should generate close to 125 BTC per core per month at current difficulty levels. For an up-front fee of 70 BTC (about $60) or more, I will direct one core at the server of your choice (I recommend a pooling service like that at mining.bitcoin.cz) for one calendar month. I will gain the certainty of paying my huge electric bill, and you will gain a better-than-80% expected profit in only a month.

If you're interested in this offer, message me with a bid... (read more)

Reply
0Kevin
I bid 33 bitcoins and all profits will go to SIAI
0imaxwell
If one other person will make an offer to round out the 70BTC, I can create a new BPM account and handle the distribution myself, returning the principal to Kevin and whomever else and sending the rest to SIAI. Edited to point out: a higher bid will still win.
5Kevin
We should have done this! How'd it go for you?
0Kevin
34 bitcoins.
[-]ata70

What are Bitcoins useful for now? About how much are they worth in dollars (if it's possible to say)? Are they currently good for anything that SingInst needs, and/or are they likely to eventually be valuable enough that it's worth possibly giving people this new excuse not to donate normal money?

Reply
9wedrifid
Buying dollars, avoiding transaction fees, dodging taxes, laundering money, maintaining anonymity and feeling nerdy.
6Wei Dai
Chart of dollar value of Bitcoin over time: http://bitcoincharts.com/charts/mtgoxUSD
5AlexMennen
This doesn't completely clear up why bitcoin is useful for SIAI. Is SIAI planning on making expenditures with bitcoins? Or is it just that giving people more different ways of donating increases the average amount that they will give, and then SIAI can just sell bitcoins for US dollars when they need money?
8lsparrish
While I don't speak for anyone at SIAI, several possibilities spring to mind. * Accepting bitcoins relatively early in the game would tend to raise the status of an organization like SIAI should it prove popular, but doesn't cost it much if it doesn't. * If the value goes up the organization can profit financially by holding onto them. * It may be the case that people will donate bitcoins more easily than equal value in dollars, for psychological reasons (e.g. lack of equivalent ugh fields). * It may be that people who initially consider donating in bitcoins will change their minds and donate dollars instead. * It could plausibly come about that processing power, and/or the time and energy of AI hackers, can be purchased more cheaply/easily for bitcoin than dollars.
8Larks
You forgot * It gives SIAI an excuse to remind everyone of the need to donate!
6Alicorn
I was recently owed some money by SIAI, and if I had been "doing" bitcoins then, I would probably have been willing to accept some fraction of my money in bitcoin form.
1RHollerith
The presence of this consideration in your list suggests that perhaps you or some of your readers do not realize that at present, there are web sites similar to foreign-exchange windows where SIAI can probably easily convert bitcoins into dollars.
0wedrifid
More likely to increase the total - probably at the expense of the average.
2Kevin
Yes... unless Clippy donates $40k!
0wedrifid
That chart shows all sorts of technical indicators. Are any of those metrics design to give an indication of how likely it is for a currency to completely collapse, based on what can be gleaned from current performance?
2Kevin
I think Bitcoin is quite unlikely to completely collapse in the next year because there are enough people with a vested interest in Bitcoin going up (namely Bitcoin miners/hoarders) that would start buying long before the value of a Bitcoin approached .1 USD.
1wedrifid
I am now somewhat curious in the abstract as to what economists have devised to predict the stability of a currency purely based of historical data. Surely there is something. Anyone familiar with the subject?
0jsalvatier
I doubt much of anything can be said about currency based only on historical data. Bitcoins are financial assets, and like other financial assets their future price behavior is very difficult to predict because expectations of future price behavior affect future price behavior.
[-]JoshuaZ60

There's another concern here. Given the general US government history of strongly not liking things like Bitcoin, (see for example what happened to e-dollar) I'm not sure being involved with bitcoin is a good idea for the long-term success of the Singularity Institute. This is activity that is possibly illegal and it may seriously damage the SI's status in the general public if it becomes associated with it.

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[-]Wei Dai140

EFF accepts donations in Bitcoin, so their lawyers must have decided that it's not clearly illegal or bad PR. On the other hand it makes sense for EFF to signal support of Bitcoin, even at some legal/PR risk, since that fits into their core mission, whereas it's much less clear what accepting donations in Bitcoin now buys SIAI. It seems unlikely to be a significant source of revenue at least in the short term.

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4SilasBarta
I'm not sure that follows. What's more, if people generally use that reasoning, and EFF is wrong (or lacked due diligence in such an estimation), then people will now be able to cite both SIAI's and EFF's actions when using such reasoning. And then you have an information cascade, where everyone believes Bitcoin "must be okay", all based on an expert judgment that never existed. Have any other cryptography experts published critiques of Bitcoin? I'd contribute to a fund to get Bruce Schneier to spend more time on this.
6Wei Dai
Perhaps you weren't aware that EFF is a "digital rights advocacy and legal organization"? If we can imagine that Bitcoin might have legal issues, how could that have escaped the people at EFF? On the other hand, SIAI is hardly known for its legal expertise, so the fact that it accepts Bitcoin offers little additional evidence for Bitcoin's legality.
6SilasBarta
Can I claim vindication on this matter now? EFF now says:
0MichaelHoward
They're now accepting it again, and even spoke at the last conference.
1SilasBarta
I'm aware of that. I'm just saying it doesn't follow that they put it through the rigorous examination you seem to imagine, given that e.g. they may not expect many such donations, had more pressing priorities, knew it would have issues but were prepared to be the test case, etc. Or maybe they just reasoned, as you are doing, that "X accepts it, so it must not have legal issues", not expecting the pseudo-evidence to cascade to others.
3Wei Dai
What I wrote originally was that EFF's lawyers must have decided that Bitcoin is not clearly illegal. You seem to have interpreted me as saying that they decided that it is clearly legal.
0SilasBarta
I'm saying that there's a lot less significance to EFF deeming something "not clearly illegal" than you were implying.
4Vladimir_M
There's actually a whole lot of significance in being endorsed by a respectable institution. As several other people have remarked in this thread, if the feds decide to throw the book at you, you're screwed no matter what. The only way to immunize yourself against this threat is to have backing by high-status people who are able to sway the public opinion and the legal establishment in your favor (so the feds will get bad press instead of accolades if they attack you, and you have a good chance to persuade a court to order the feds to leave you alone). EFF is far from being a decisively powerful player in this regard, but getting its endorsement is definitely a large step in the direction favorable for the Bitcoin people.
4SilasBarta
Again, I agree there are benefits, I just dispute their characterization by Wei_Dai et al. EFF is not "endorsing" Bitcoin in the sense usually meant; they're saying they'll accept donations that way. There's a huge difference between that and "Oh, but these respectable lawyer guys told this big organization it'd be okay!" Anyway, I did join up. If you look at the map of users, I'm the singular dude in Waco.
7Wei Dai
The Activism Director of EFF wrote a substantial blog post on Bitcoin, calling it "a step toward censorship-resistant digital currency". Earlier, they had another post listing Bitcoin as a project that "digital activists" should contribute to. ETA: Even without these explicit endorsements, it seems obvious to me that a prominent activism/lobbying/legal organization does not just do something like accept donations in Bitcoin without considering what kind of signal that sends.
1Wei Dai
The point of that comment was that Bitcoin is not clearly illegal but there are legal/PR risks, and it's not clear why SIAI is choosing to take those risks. How much "less significance" could I have implied?
0Pavitra
Most people don't rationally weigh evidence, but rather examine the status of who supports each side. The nature of EFF and SIAI is less relevant here than their popularity.
0Douglas_Knight
There is very little more to being legal than an information cascade.
3SilasBarta
Sure, as long as it becomes expansive enough. My concern is if it cascades the geek community while still seeming weird and criminal to the rest of the world.
2wedrifid
More affiliation with the mastermind behind cryptocurrency. :)
4Dorikka
Your link doesn't indicate that users of e-gold were found to have been in any violation of the law -- the only thing that I saw happened to people who had not been violating the law in some other manner was that 56 accounts were locked/blocked (though I'm not sure why these were blocked, since it looks like they were just e-gold/money traders.) Do you see any specific legal hazard for users that I don't?
1JoshuaZ
There have been a few others discussed in this thread and in the other thread on Bitcoin. They include the argument that since individual users are making the currency they are counterfeiting (plausible legal argument), or that each individual is acting as a bank(weak), or that all users of Bitcoin together make up an organization for purposes of RICO (plausible). Since Bitcoin is not as centralized as e-coins it is much more plausible that a government response would go against actual users rather than any central organization. In any event, the primary problem for the SIAI would probably be the public status hit if there do end up being legal issues, not the actual legal complications.
2wedrifid
Counterfeiting is less plausible than the banking claim, not more.
0handoflixue
Given that WOW has it's own virtual currency, with a fairly brisk USD-WOW exchange existing (albeit in violation of a EULA), I'd say the counterfeiting claim does indeed seem very unlikely. Certainly, I've never heard of actual criminal charges - the few Google results for arrests seem to be from other countries or other crimes that just incidentally used WOW Gold.
3Nick_Tarleton
Is there a specific reason to think so? It doesn't look like any e-gold users were prosecuted, or like the grounds for prosecuting the operators of e-gold would generalize.
3John_Maxwell
Bitcoin is designed specifically so there is no central agency to prosecute. So who would the government go after aside from the users? Furthermore, if SIAI is involved with Bitcoin and Bitcoin undergoes some sort of legal investigation, I speculate SIAI might as well just because the FBI thought that they looked interesting. This feels like it would be a Bad Thing.
2katydee
Generally speaking I don't think the FBI investigates things "just because they look interesting," and since SIAI (to the best of my knowledge) isn't doing anything illegal that's not particularly worrisome anyway.
1wedrifid
Unless they are taken seriously, in which case there is most likely a law there somewhere that they could be said to be violating. They are, after all, trying to create a weapon of mass destruction. :)
1katydee
What? No they aren't, they're trying to establish protocols within which a general artificial intelligence can be safely created. Whether a general artificial intelligence should qualify as a weapon of mass destruction is a different argument, but it certainly doesn't qualify as one from a legal point of view, and if the SIAI safety/friendliness plan works, it shouldn't from a practical point of view either!
4wedrifid
I'm not nearly so confident. The Powers That Be don't need to be all that reasonable about these things. Because of the bit about the Power. I expect a security oriented government body would be able to come up with as many ways for creating a superintelligence to be illegal as MoR!Harry could find ways to weaponise Hufflepuffs. Calling it a WoMD would just be one of them.
4katydee
It's conceivable that, at some point, building design frameworks for friendly artificial intelligences (or, more plausibly, artificial intelligences in general) might be made illegal, but it certainly isn't illegal now.
3handoflixue
http://en.wikipedia.org/wiki/Steve_Jackson_Games,_Inc._v._United_States_Secret_Service Legality really doesn't seem to be a huge factor in whether the Secret Service can inconvenience you. And if they raided a gaming company, I could see them plausibly raiding an AI development organization. That said, I don't see anything to suggest it's particularly likely, but a government investigation, all by itself, is incredibly disruptive even if you don't end up guilty of any crimes. Edit: Fixed from FBI to Secret Service.
-1wedrifid
Edit: Response was written to original (brief) version of the parent (quoted below). Encryption software has, at times, been legally declared 'munitions', the export of which can be a serious crime. Since an AI actually could be deployed as a weapon - and even a 'Friendly' version will be perceived to be causing massive destruction by at least one interest group - throwing that sort of label around would be comparatively reasonable. Not that I would make that designation. But I'm not a paramilitary organisation with relevant official status. As for things that are not Weapons of Mass Destruction, try biological and chemical weapons (of the kind that actually exist). If you want to cause mass destruction use a nuke. Don't have one of them? Use conventional explosives. If you want to do serious damage with a chemical weapon... pick a chemical that explodes. That phrase is broken.
1Eugine_Nier
Well building an AI to take over the world would arguably qualify as plotting violent overthrow of the government.
2Pavitra
I'd guess they would go after a few particularly high-volume, high-profit, high-profile traders like Mt. Gox, because this is the basic strategy used against Bittorrent.
2RHollerith
The government's response to a currency or payment system that could be shut down by shutting down a single "point of failure" is not particularly informative for predicting its response to a payment system that does not have a single point of failure. The government correctly perceives allowing the man in the street to transact business or earn money outside of the awareness and control of the regulated banking system to be a threat to its revenue stream and to be an enabler of crime and terrorism.
4wedrifid
That the government is likely to spin or outright create laws to protect its interests is a different thing to "this activity is possibly illegal". I was given related advice while a cofounder of a startup venture. Forget whether you are legally in the right. If a powerful competitor is threatened they can sue on a vaguely credible premise they can destroy either your company or years of your life regardless of whether their superior lawyers foist it past the judge. The letter of the law just doesn't matter all that much if there is a power imbalance.
2JoshuaZ
The government could if they wanted to go after individuals on counterfeiting charges. See also the remark by pjeby about banking laws (although as I said there, that seems hard to pin down). Unfortunately there are a large number of different federal laws about money and taxes, so it shouldn't be that hard to find some federal crime to use. There may also be ways of tying in RICO charges which could be potentially used to then prosecute anyone using Bitcoin based on the most illegal activity of anyone using Bitcoin (so murder for hire, drug running, kidnapping, etc. from anyone on the network could potentially result in charges for anyone on the network.) In general, when the feds want something to be illegal and it involves money, they'll find a way.
3Kevin
EGold was a for profit corporation with operations conducted from Florida. Bitcoin is an open source project.
-2Kevin
Why would the US government go after Bitcoin? Indicting the directors of e-gold was one of the greatest accomplishments of Bush's Department of Justice and hopefully we will never again see such an insane justice department. Also, there is no US entity to even prosecute, just an IRC channel to gain control of. Some cyberpunk future where the world governments are trying to hack Bitcoin is almost more likely than any of the users being sued for things for things other than committing crimes while happening to be using Bitcoin at the same time.
3JoshuaZ
The government generally frowns on alternative modes of currency that aren't in their power. They really aren't going to like a form that is essentially untraceable. Either one of those would be enough for the government to be unhappy with. I'm also pretty sure that e-gold was very low down on Justice's priority list during Bush, and it doesn't take an "insane justice department" just a government that wants to be able to track money, control the size of the money supply, and be able to effectively tax. When confronted with a problem, do you first try to use your existing skills and powers to solve a problem or others? Now, what ability do federal prosecutors have that most of the world doesn't? (Hint:The correct answer is not "an army of skilled of hackers".)
[-]RHollerith60

Who is behind Bitcoin and what are their declared goals?

What makes them believe governments will not be able to stop the use of Bitcoins in the developed world if Bitcoins get significant traction? Is the goal to get traction in the developed world in the hopes of converting that temporary traction into a persistent presence (on smartphones since computers are not widely deployed there) in failed states and weak states?

(If it gets significant traction, I consider some first-world government's not wanting to shut Bitcoin down as so unlikely as to be not worth explicitly asking after.)

Reply
4Clippy
What government attack vectors against Bitcoin do you deem most likely to work? (There is probably a discussion thread on the Bitcoin forums on this matter.) One obvious (and rather covert) method to undermine Bitcoin is to apply sufficient computational power before the computational power of honest users becomes prohibitive. This would permit a wealthy government to perhaps double-spend bitcoins, undermining the entire network. An overt method would be to join, and then try to track down (via ISPs) the user associated with every public key.
4JoshuaZ
Simplest attack: just make it illegal and prevent people from converting bitcoins into cash. If it isn't connected to the larger economy not many people will be interested in it.
[-]pjeby150

Simplest attack: just make it illegal

Why bother, when they can just use existing laws? Classify bitcoin users as banks, then fine them for violating existing transaction-reporting laws. Tax violations. I'm sure there are dozens if not hundreds of regulations that someone can be charged with.

Not reporting income or profit. Not reporting what you paid to other people that should be counted as their income, and so on. The US seems especially hostile to this sort of thing, what with the number of post-9/11 financial regulations added. I daresay they won't be happy that anyone can just become their own bank and not fill out any paperwork at all... let alone the relative impossibility of remotely freezing someone's account or seizing their assets, without first involving every third party they might trade with.

I expect that some clever lawyering and accountancy will be necessary to protect bitcoin users from legal harassment in the future, and that the only thing protecting them now is the relatively low-key nature of the stuff. But it's only a matter of time until the media begin the blitz to portray Bitcoin as a tool of terrorists, druggies, black-hat hackers, gunrunners, money launderers, and whoever else will scare their viewers via guilt-by-association. Oh yeah, I forgot to mention pornographers, and by extension, human traffickers and child molesters. That'll be enough to get political support for a crackdown, I imagine.

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4JoshuaZ
IANAL but I think that a court might not look kindly on an argument that turns every person who is using something into a bank. The decentralized nature undermines that argument. As to reporting, there's no reason in principle that bitcoin users can't report the money they owe for taxes and the like. More of a problem if you pay an anonymous individual for some service, but that's less of an issue if you aren't hiring them for an extended period of time. Unfortunately, if bitcoin ever becomes very popular, then it will be reasonable for the people who really don't want a government eye on them to use it. Undermining authority works both ways: it might be nice for us but it can benefit those one doesn't like also. At present, terrorists/guerrillas/freedom fighters/militants use complicated and cumbersome procedure to moving money around. Bitcoin could offer them a strong leg up. The most dangerous type of media-driven moral panics are the ones that have some element of truth.
0wedrifid
For example, they could be using one of a dozen or so other sufficiently anonymous electronic currencies that are already available.
0RHollerith
If you have evidence of the existence of electronic currencies heavily and successfully used by criminals and terrorists, will you please share?
0wedrifid
This is not actually what I claimed.
0RHollerith
OK. What did you claim, then?
1wedrifid
Pardon me, the word 'could' was missing, distorting my intended meaning. Edited. I claim that the for the purposes of criminal activities the existing more popular electronic currencies are just as effective as bitcoin would be. Now that you mention it I would claim that criminals use anonymous online currencies. Online currencies are notorious for money laundering. I have no idea what terrorists in particular currently do. Just what online resources they have available.
3sfb
From Wikipedia: So I would transact the heck out of it and make the database huge. IIRC at the moment every user needs a full copy of the database of every transaction, so if the .gov can make a multi-terabyte database a requirement, that would knock it on the head quite hard. Also, the last time I glanced at the source code it looked quite ropey, and that makes me think it will have lots of exploitable parts lurking for the right skilled people to find and attack.
2Clippy
Do users need to store the Merkle tree only, or the full database? If they only need to store the Merkle tree, then could the network proportionally counteract the effect of this database lengthening by increasing the datablock length? Does use of a Merkel tree reduce the fraction of the database that each user needs to store?
[-]Kevin60

If anyone is in a situation where they have unmetered electricity (college dorm, etc.) and a desktop computer that can fit a high-end graphics card and mine 24/7 and donate to SIAI, I'll probably buy a Radeon HD 5870 to loan to you for six months or so.

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[-]Larks110

Updating on the implied value of this activity to SIAI, I precommit to donate £10 to SIAI if I haven't seriously looked into mining in a weeks time. If I look into it and reject it, I will explain my reason not to.

Reply
2Kevin
poke
2Larks
Did look into it, probably will run in term time (free electricity), but nonetheless paypalled; screenshot on request/you can ask Amy
-1Clippy
Can you loan me the money to buy a Radeon HD 5870 and hook up to my ape-designed computer so I can mine Bitcoins?
3Kevin
I could, but the signalling of accepting this deal seems bad since if you don't have $200 to spare right now it seems unlikely that you will have $49,000 within the next year. One HD 5870 definitely isn't enough to generate that many Bitcoins.
1Clippy
I have over 200 USD now, I just wanted someone else to finance it.
0wedrifid
You would, I suspect, have to specify how many bitcoins you would be wiling to donate to the SIAI or to Kevin by way of compensation for the hardware. With a suitably cheap power supply available it is plausible that both you and Kevin could profit from such an arrangement.
[-]imaxwell50

There's a bitcoin escrow service called ClearCoin that includes the option of sending escrowed funds to one of their listed nonprofits, rather than back to the payer, if the escrow expires. I asked the site owner to include the SI donation address as an option and have been using it since.

Unfortunately for SI, everyone I've dealt with has been honest so far! I'll have to actually donate on purpose instead of incidentally, it seems.

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4imaxwell
Update: 14.01 bitcoins are "in the mail" (read: sitting in ClearCoin waiting for the transaction to expire). At current exchange rates, that's around $100.
[-]Clippy50

I accept Bitcoin donations too. My address is:

16eyVtgaTYGxstybeay9mQ6xy4GAPVtXLN

Also, are there any jobs I can perform for Users here in exchange for Bitcoin? (Does that topic deserve its own thread?) Since User:Kevin has promised to accept Bitcoins as payments on our deal, this makes it tremendously easier for me to pay User:Kevin.

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4gwern
It's certainly interesting to read these comments with the benefit of an additional two and a half years of information.
2yli
https://blockchain.info/address/1HUrNJfVFwQkbuMXwiPxSQcpyr3ktn1wc9:
2MichaelHoward
Apparently that's old. The address currently on their website is https://blockchain.info/address/1BszW45pwXx7d7g4x9Xxbs9MGJEQcJsd3v although that hasn't received any coins yet. Maybe the old one is fine too, but unless someone can shed light on why they changed from the old address, it's probably best not to send coins to it, although I'd hope if it had become unsafe they would have announced it loudly.
[-]VNKKET40

This makes me happy. Now, here's a question that is probably answered in the technical paper, but I don't have time to read it:

"New coins are generated by a network node each time it finds the solution to a certain calculational problem." What is this calculational problem? Could it easily serve some sinister purpose?

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3nshepperd
Not easily. As I understand it, the problem is finding bit strings with a sha256 hash whose (256-bit) numerical value is less than a certain number. In addition, part of what goes into the bit string is the bitcoin address of the person who will keep the newly generated coins. I can't imagine a way to exploit that for any useful purpose, sinister or otherwise.
0Clippy
I am a bit confused. Why would this process need to be continually re-done? Once you have generated all the hashes of numbers less than 256 bits long, then you instantly (up to the speed of accessing the database entry) know a short preimage for every hash value.
2alethiophile
That's not the idea. The computational problem is simply a proof of work--you create a specific, verifiable string, with a changeable component greater than 256 bits, then hash that string using incrementing values until you find a SHAsum less than a certain value. Knowing a random, short preimage for each possible hash doesn't help you there, because those will not allow you to create a verifiable string with the correct hash.
2JoshuaZ
Generating all those hashes and storing them? Good luck. 2^256 is about 10^77. For comparison there are on the order of 10^50 atoms on Earth. There's no way you are making a look-up table for every number less than 256 bits.
0pengvado
Rainbow tables allow you to choose a tradeoff between storage and speed. So if you wanted to do that (which is of course unrelated to Bitcoin), the actual constraint is: (table size) * (number of hash calls to invert one hash value) = 2^256.
1JGWeissman
So, if you magically transformed the Earth into a giant rainbow table that uses N atoms to store a key value pair, you would have to perform N*10^27 hash calls to invert one hash value. Not very useful in this case.
0Clippy
Then what method do the Bitcoin users use to find the (sufficiently short) preimage of the hash values they are working, if indeed the problemspace is that big and sha256 is designed so that the mapping from the output to the input is as complex as possible? And is it possible for a user to generate Bitcoins faster by discovering a better algorithm for inverting sha256 hashes?
0JoshuaZ
I must be missing something. Why do you think they are inverting the hashes?
0Clippy
I thought that's what the proof of work entailed. As User:nshepperd put it: As best I can tell, it sounds like there some has value, and you must find an inverse (preimage) for it that meets certain criteria (like being less than a certain value). So doesn't the problem involve finding hash inverses as the proof of work? Or at least computing a huge number of hashes until one is found that matches a target hash?
0JoshuaZ
If I'm reading this correctly you don't need a specific hash result, just a hash that is less than a specific number. That's much easier to find.
0Clippy
Oh, so it's the hash itself that must be less than a specific value, not the preimage of the hash. Still, that can be rephrased as "inverting any one of the hashes that are below a certain value", which is why I kept mapping it to a hash inversion problem. And the only known way to do this is to try a large number of bitstrings and see what their hashing yields? Is there a known way to more efficiently search by looking what what bitstrings are likely to have hashes with zeroes in the most significant digits? Could someone improve performance by finding such a method?
5JGWeissman
Hashcodes do not have unique inverses. The goal is not just to find any bitstring with a haschcode in the target interval (in which case the solutions would be trivially reusable), but to find such a bitstring that contains information, including a hashcode of the previous block (so you can't get a head start before that block is computed) and transactions to be recorded (so your block is actually useful to the community).
2JoshuaZ
Yes, but much easier. Let's say for example, that you want the first 3 digits of your hash to be zero. Then if the hashes are randomly distributed (and they should be) such a hash will occur once every 1000 hashes. In contrast, trying to invert a specific hash is much more difficult. If there were a way to quickly figure out which hashes have a lot of zeros that would probably be close to making the hash cryptographically broken. Finding such a method isn't the same as finding collisions but it is in the same class of general results. I don't know the exact details of the process used but I'd be surprised if there were any known way of approaching this other than direct computation.
[-]imaxwell10

I got 0.05 BTC from the Bitcoin Faucet. It looks like there's nothing meaningful I can do with 0.05 BTC, and I'm not certain I'll ever have more, so I'm donating it to SIAI instead of back to the Faucet.

I'm really just posting this so that the 0.05 BTC donation doesn't come off as the signalling equivalent of a 10-cent tip. If I do make more BTC, I'll donate at least some of that as well. (Actually, donating all of it sounds like a good way to avoid annoying tax questions, so I'm considering that.)

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[-]lsparrish10

Marc Bevand has written an interesting article which describes how bitcoin works, and how the computing power applied to it has been doubling every 27 days. It is also apparently being used for illegal trading already.

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