Re: [Bitcoin-development] Economics of information propagation
> Of course, in reality smaller miners can just mine on top of block headers > and include no transactions and do no validation, but that is extremely > harmful to the security of Bitcoin. If it's only during the few seconds that it takes to to verify the block, then would this really be that big of a deal? E.g. even if all miners did this, a 10 second delay would only yield an average of a couple blind/empty blocks per day. On Sun, Apr 20, 2014 at 10:06 PM, Peter Todd wrote: > -BEGIN PGP SIGNED MESSAGE- > Hash: SHA256 > > That is mistaken: you can't mine on top of just a block header, leaving > small miners disadvantaged as they are earning no profit while they wait > for the information to validate the block and update their UTXO sets. This > results in the same problem as before, as the large pools who mine most > blocks can validate either instantly - the self-mine case - or more quickly > than the smaller miners. > > Of course, in reality smaller miners can just mine on top of block headers > and include no transactions and do no validation, but that is extremely > harmful to the security of Bitcoin. > > > On 20 April 2014 23:58:58 GMT-04:00, Mark Friedenbach > wrote: > >As soon as we switch to headers > >first - which will be soon - there will be no difference in propagation > >time no matter how large the block is. Only 80 bites will be required > >to > >propagate the block header which establishes priority for when the > >block is > >fully validated. > >On Apr 20, 2014 6:56 PM, "Jonathan Levin" > > > >wrote: > > > >> Hi all, > >> > >> I am a post-graduate economist writing a paper on the incentives of > >> mining. Even though this issue has been debated in the forums, I > >think it > >> is important to get a sense of the magnitude of the incentives at > >play and > >> determine what implications this has for the transaction fee market. > >> > >> As it has been pointed out before the marginal cost for miners does > >not > >> stem from the private cost of the miner validating the signature and > >> including it in the list of transactions in the block but rather the > >> increased probability that the block will be orphaned as a result of > >slower > >> propagation. Gavin did some back of the envelope worst case > >calculations > >> but these overstated the effect of propagation delay. The reason > >being the > >> 80ms additional time to reach 50% of the network is spread throughout > >the > >> time that it takes to reach 50% of the network. During this time > >miners are > >> notified about the block and treat it as the longest chain and hence > >are no > >> longer mining with the aim to produce a competing block. > >> > >> I am looking to calculate the change in the curvature of the > >probability > >> mass function that a block hears about my block in any given second > >as a > >> function of the block size. Although there is likely to be > >significant > >> noise here, there seems to be some stable linear relationships with > >the > >> time that it takes to reach different quartiles. Has anyone done > >this? I > >> have used some empirical data that I am happy to share but ideally I > >would > >> like analytical solutions. > >> > >> Following Peter Todd, I also find the concerning result that > >propagation > >> delays results in increasing returns to higher shares of the hashing > >power. > >> Indeed it may well be in the interest of large pools to publish large > >> blocks to increase propagation delays on the network which would > >increase > >> orphan rates particularly for small miners and miners that have not > >> invested in sufficient bandwidth / connectivity. If a small miner > >hears > >> about a block after 4.5 seconds on average there is a 0.7% chance > >that > >> there is already a block in circulation. Large miners can increase > >the > >> time that it takes for small miners to hear about blocks by > >increasing the > >> size of their blocks. For example if the time that it takes for a > >small > >> miner to hear about the block goes to 12 seconds there is a 2 percent > >> chance there is already a block in circulation for the small miner. > >There > >> is also a 1.2% chance that there will be a competing block published > >after > >> a small miner propagates in the time that it gets to full > >propagation. Am I > >> getting this right that the probability of a miner’s block being > >orphaned > >> is comprised of the probability that the miner was not the first to > >find a > >> valid block and the probability that given they are first, someone > >else in > >> the absence of hearing about it finds a competing valid block. > >> > >> One question is: Are orphans probabilistic and only resolved after > >hearing > >> about a new block that lengthens the chain or is there a way to know > >in > >> advance? Is it frowned upon to mine on top of a block that you have > >just > >> found even though it is very likely going to end up an orphan? > >> > >> Would be happy to share
Re: [Bitcoin-development] we can all relax now
Hey Peter, something seems wrong with your above analysis: I think a miner would withhold his block not because it leads to a greater probability of winning the next one, but because it increases his expected revenue. Suppose a cabal with fraction q of the total hashing power is n blocks ahead on a secret branch of that has mined r_tot coins, and let r_next be its next block's reward. If the cabal chooses not to broadcast its secret chain until at least the next block, its expected revenue after the next block is found is (1 - (1-q)^(n+1))*(r_tot + r_next) If it does broadcast, its expected revenue after the next block is found is r_tot + q * r_next If the cabal seeks only to maximize immediate revenue, then after a bit of algebra we find that it will withhold its chain if q > 1 - ( 1 + r_tot / r_next )^(-1/n) So if the cabal has just mined his first block off of the public chain, i.e. n = 1, and if the block reward is relatively stable, i.e. r_next = r_tot, then it needs q > 50% to profitably withhold, not the 29.2% you calculated. >From this formula we can also see that if the miner wins the race and withholds again, then he must grow q to compensate for the increase in r_tot, and any decrease in n. So generally publication becomes increasingly in the cabal's interest, and secret chains will tend not to grow too large (intuition tells me that simulations using the above formula should bear this out). This seem correct to you? On Thu, Nov 7, 2013 at 9:14 AM, Mike Hearn wrote: > Once the ASIC race calms down because everyone has one, has more or less > optimal power supplies, process improvements aren't easily reachable > anymore etc then I'd expect people to dissipate from the large pools > because eliminating their fees will become the next lowest hanging fruit to > squeeze out extra profit. There's no particular reason we need only a > handful of pools that control a major fraction of the hashpower. > > If we end up with a few hundred pools or lots of miners on p2pool, then a > lot of these theoretical attacks become not very relevant (I don't think ID > sacrifices will be so common or large as to justify a pile of custom mining > code+strategies at any point ...) > > > On Thu, Nov 7, 2013 at 2:24 PM, Peter Todd wrote: > >> On Thu, Nov 07, 2013 at 02:56:56PM +1000, Gavin Andresen wrote: >> > > P.S: If any large pools want to try this stuff out, give me a shout. >> You >> > > have my PGP key - confidentiality assured. >> > > >> > >> > If I find out one of the large pools decides to run this 'experiment' on >> > the main network, I will make it my mission to tell people to switch to >> a >> > more responsible pool. >> >> I hope they listen. >> >> A few months ago ASICMiner could have made use of that attack if my >> memories of their peak hashing power were correct. They certainely could >> have used the selfish miner version, (we need better name for that) >> although development costs would eat into profits. >> >> GHash.IO, 22%, says they're a "private Bitfury ASIC mining pool" - dunno >> what they mean by that, but they're involved with CEX.IO who has >> physical control of a bunch of hashing power so I guess that means their >> model is like ASICMiners. They're a bit short of 30%, but maybe some >> behind-the-scenes deals would fix that, and/or lowering the barrier with >> reactive block publishing. (a better name) >> >> > And if you think you can get away with driving up EVERYBODY's orphan >> rate >> > without anybody noticing, you should think again. >> >> ...and remember, if you only do the attack a little bit, you still can >> earn more profit, and only drive up the orphan rate a little bit. So who >> knows, maybe the orphans are real, or maybe they're an attack? ASICMiner >> was involved with a bunch of orphans a while back... >> >> You know what this calls for? A witchhunt! >> >> BURN THE LARGE POOLS! >> >> > > P.P.S: If you're mining on a pool with more than, like, 1% hashing >> > > power, do the math on varience... Seriously, stop it and go mine on a >> > > smaller pool, or better yet, p2pool. >> > > >> > >> > That I agree with. >> >> Glad to hear. >> >> -- >> 'peter'[:-1]@petertodd.org >> 0007bd936f19e33bc8b8f9bb1f4c013b863ef60a7f5a6a5d2112 >> >> >> -- >> November Webinars for C, C++, Fortran Developers >> Accelerate application performance with scalable programming models. >> Explore >> techniques for threading, error checking, porting, and tuning. Get the >> most >> from the latest Intel processors and coprocessors. See abstracts and >> register >> >> http://pubads.g.doubleclick.net/gampad/clk?id=60136231&iu=/4140/ostg.clktrk >> ___ >> Bitcoin-development mailing list >> Bitcoin-development@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/bitcoin-development >> >> > > > ---
Re: [Bitcoin-development] Identity protocol observation
Names clearly solve a different problem than that, but we still use them, so they must be solving _some_ problem :p In this case they're a unique identifier humans can remember after a bit of use and easily communicate to each other with little room for error. Securely mapping them to public keys would make key verification simpler. Simpler than checking a much larger key fingerprint, at least. Like I said, it's probably a niche product ;) I used to remember dozens of phone numbers before my phone did it for me, but maybe I was just weird. On Thu, Oct 3, 2013 at 9:22 AM, Mike Hearn wrote: > 1) Generate sacrifice proof file using an app > 2) Load file into browser > 3) Surf > > Where are the names in that design? I'm not sure where NameCoin comes into > this. The point of a sacrifice is it's an anonymous identity, there's no > point attaching a name to it. > > BTW I keep phone numbers in an address book ;) > > > > > On Thu, Oct 3, 2013 at 5:16 PM, Daniel Lidstrom wrote: > >> Fair enough, though people still manage okay with phone numbers. And a >> decentralized naming system seems to come at great cost - with namecoin you >> need the whole blockchain to resolve names without trust. Strip out a bell >> and whistle - meaningfulness and transferability of names - and you get a >> simple, rudimentary (spam killing!) system that scales on any device. I'll >> only argue that it seems to be Good Enough *for the types of people who >> might care about decentralized names*. Probably a very small set :) >> >> >> On Thu, Oct 3, 2013 at 8:00 AM, Mike Hearn wrote: >> >>> Interesting observation, thanks. >>> >>> I'd think any competent implementation of such an identity scheme would >>> not involve end users directly handling randomized nonsense words, however. >>> I always imagined a sacrifice as being a file that you make with a GUI tool >>> and load into a browser extension. >>> >>> >>> On Thu, Oct 3, 2013 at 3:35 PM, Daniel Lidstrom wrote: >>> >>>> A couple more thoughts on this: >>>> >>>> 1) Both c and k can be kept if c is pronounced 'ch', giving ~10.9 bits >>>> per phoneme. >>>> 2) An extra phoneme (4 encode 43 bits total) gives room to put extra >>>> information into the name, e.g. the first 5 bits could be input as the key >>>> to a PRP that permutes the last 38 back to a standard encoding of a tx >>>> location. This would give the user 32 random names per sacrifice to choose >>>> from, and 38 bits to encode its location in the blockchain, which is enough >>>> for pretty large blocks. >>>> >>>> Sample 4 phoneme names: >>>> ~milmoz-vyrnyx >>>> ~mypnoz-fojzas >>>> ~sawfex-bovlec >>>> ~fidhut-guvgis >>>> ~bobfej-jessuk >>>> ~furcos-diwhuw >>>> ~wokryx-wilrox >>>> ~bygbyl-caggos >>>> ~vewcyv-jyjsal >>>> ~daxsaf-cywkul >>>> >>>> They're not that bad IMHO, especially if you get to pick a decent one >>>> from a bunch. >>>> >>>> >>>> On Thu, Oct 3, 2013 at 3:35 AM, Daniel Lidstrom >>>> wrote: >>>> >>>>> The location of a tx in the blockchain can be encoded in >>>>> n=log2(h)+log2(t) bits, where h is the block height, and t is the number >>>>> of >>>>> transactions in the block. Currently h~250,000 and t~500, so n~27. A CVC >>>>> phoneme encodes ~10.7 bits *, so a transaction today can be located in the >>>>> blockchain with 3 of these, e.g. reb-mizvig. This is reasonably short, >>>>> readable and memorable. >>>>> >>>>> The identity protocol Jeff Garzik is working on will link a public key >>>>> fingerprint to a miner sacrifice transaction. This tx could in turn be >>>>> uniquely described with a short name as above. Associating this name with >>>>> the public key becomes secure once the tx is sufficiently buried in the >>>>> blockchain. In the identity protocol, lightweight clients check the >>>>> validity of a sacrifice tx by checking that its merkle path is valid. But >>>>> this path encodes, via the ordering of the hashes at each level, the >>>>> location of the transaction in the block, so the lightweight client can >>>>> verify the sacrifice tx's short name using only the information he already >>>>> has. >>
Re: [Bitcoin-development] Identity protocol observation
Fair enough, though people still manage okay with phone numbers. And a decentralized naming system seems to come at great cost - with namecoin you need the whole blockchain to resolve names without trust. Strip out a bell and whistle - meaningfulness and transferability of names - and you get a simple, rudimentary (spam killing!) system that scales on any device. I'll only argue that it seems to be Good Enough *for the types of people who might care about decentralized names*. Probably a very small set :) On Thu, Oct 3, 2013 at 8:00 AM, Mike Hearn wrote: > Interesting observation, thanks. > > I'd think any competent implementation of such an identity scheme would > not involve end users directly handling randomized nonsense words, however. > I always imagined a sacrifice as being a file that you make with a GUI tool > and load into a browser extension. > > > On Thu, Oct 3, 2013 at 3:35 PM, Daniel Lidstrom wrote: > >> A couple more thoughts on this: >> >> 1) Both c and k can be kept if c is pronounced 'ch', giving ~10.9 bits >> per phoneme. >> 2) An extra phoneme (4 encode 43 bits total) gives room to put extra >> information into the name, e.g. the first 5 bits could be input as the key >> to a PRP that permutes the last 38 back to a standard encoding of a tx >> location. This would give the user 32 random names per sacrifice to choose >> from, and 38 bits to encode its location in the blockchain, which is enough >> for pretty large blocks. >> >> Sample 4 phoneme names: >> ~milmoz-vyrnyx >> ~mypnoz-fojzas >> ~sawfex-bovlec >> ~fidhut-guvgis >> ~bobfej-jessuk >> ~furcos-diwhuw >> ~wokryx-wilrox >> ~bygbyl-caggos >> ~vewcyv-jyjsal >> ~daxsaf-cywkul >> >> They're not that bad IMHO, especially if you get to pick a decent one >> from a bunch. >> >> >> On Thu, Oct 3, 2013 at 3:35 AM, Daniel Lidstrom wrote: >> >>> The location of a tx in the blockchain can be encoded in >>> n=log2(h)+log2(t) bits, where h is the block height, and t is the number of >>> transactions in the block. Currently h~250,000 and t~500, so n~27. A CVC >>> phoneme encodes ~10.7 bits *, so a transaction today can be located in the >>> blockchain with 3 of these, e.g. reb-mizvig. This is reasonably short, >>> readable and memorable. >>> >>> The identity protocol Jeff Garzik is working on will link a public key >>> fingerprint to a miner sacrifice transaction. This tx could in turn be >>> uniquely described with a short name as above. Associating this name with >>> the public key becomes secure once the tx is sufficiently buried in the >>> blockchain. In the identity protocol, lightweight clients check the >>> validity of a sacrifice tx by checking that its merkle path is valid. But >>> this path encodes, via the ordering of the hashes at each level, the >>> location of the transaction in the block, so the lightweight client can >>> verify the sacrifice tx's short name using only the information he already >>> has. >>> >>> Some more random names: >>> vec-halhic >>> wom-vizpyd >>> guv-zussof >>> jog-copwug >>> seg-rizges >>> jyg-somgod >>> pax-synjem >>> zyg-zuxdyj >>> gid-mutdyj >>> rel-hyrdaj >>> >>> Sources of inspiration: >>> urbit.org >>> https://en.bitcoin.it/wiki/Identity_protocol_v1 >>> >>> * This is somewhat restricted: I disallowed q for obvious reasons and k >>> because it conflicts with c, and c looks much softer and less like >>> Klingon. H is allowed for the first consonant, but not the second, and x >>> is allowed for the last one, but not the first one. Y is a vowel, but not >>> a consonant. Maybe these weren't quite the right choices. Paint away! >>> >> >> >> >> -- >> October Webinars: Code for Performance >> Free Intel webinars can help you accelerate application performance. >> Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most >> from >> the latest Intel processors and coprocessors. See abstracts and register > >> >> http://pubads.g.doubleclick.net/gampad/clk?id=60134791&iu=/4140/ostg.clktrk >> ___ >> Bitcoin-development mailing list >> Bitcoin-development@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/bitcoin-development >> >> > -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register > http://pubads.g.doubleclick.net/gampad/clk?id=60134791&iu=/4140/ostg.clktrk___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development
Re: [Bitcoin-development] Identity protocol observation
A couple more thoughts on this: 1) Both c and k can be kept if c is pronounced 'ch', giving ~10.9 bits per phoneme. 2) An extra phoneme (4 encode 43 bits total) gives room to put extra information into the name, e.g. the first 5 bits could be input as the key to a PRP that permutes the last 38 back to a standard encoding of a tx location. This would give the user 32 random names per sacrifice to choose from, and 38 bits to encode its location in the blockchain, which is enough for pretty large blocks. Sample 4 phoneme names: ~milmoz-vyrnyx ~mypnoz-fojzas ~sawfex-bovlec ~fidhut-guvgis ~bobfej-jessuk ~furcos-diwhuw ~wokryx-wilrox ~bygbyl-caggos ~vewcyv-jyjsal ~daxsaf-cywkul They're not that bad IMHO, especially if you get to pick a decent one from a bunch. On Thu, Oct 3, 2013 at 3:35 AM, Daniel Lidstrom wrote: > The location of a tx in the blockchain can be encoded in n=log2(h)+log2(t) > bits, where h is the block height, and t is the number of transactions in > the block. Currently h~250,000 and t~500, so n~27. A CVC phoneme encodes > ~10.7 bits *, so a transaction today can be located in the blockchain with > 3 of these, e.g. reb-mizvig. This is reasonably short, readable and > memorable. > > The identity protocol Jeff Garzik is working on will link a public key > fingerprint to a miner sacrifice transaction. This tx could in turn be > uniquely described with a short name as above. Associating this name with > the public key becomes secure once the tx is sufficiently buried in the > blockchain. In the identity protocol, lightweight clients check the > validity of a sacrifice tx by checking that its merkle path is valid. But > this path encodes, via the ordering of the hashes at each level, the > location of the transaction in the block, so the lightweight client can > verify the sacrifice tx's short name using only the information he already > has. > > Some more random names: > vec-halhic > wom-vizpyd > guv-zussof > jog-copwug > seg-rizges > jyg-somgod > pax-synjem > zyg-zuxdyj > gid-mutdyj > rel-hyrdaj > > Sources of inspiration: > urbit.org > https://en.bitcoin.it/wiki/Identity_protocol_v1 > > * This is somewhat restricted: I disallowed q for obvious reasons and k > because it conflicts with c, and c looks much softer and less like > Klingon. H is allowed for the first consonant, but not the second, and x > is allowed for the last one, but not the first one. Y is a vowel, but not > a consonant. Maybe these weren't quite the right choices. Paint away! > -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register > http://pubads.g.doubleclick.net/gampad/clk?id=60134791&iu=/4140/ostg.clktrk___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development
[Bitcoin-development] Identity protocol observation
The location of a tx in the blockchain can be encoded in n=log2(h)+log2(t) bits, where h is the block height, and t is the number of transactions in the block. Currently h~250,000 and t~500, so n~27. A CVC phoneme encodes ~10.7 bits *, so a transaction today can be located in the blockchain with 3 of these, e.g. reb-mizvig. This is reasonably short, readable and memorable. The identity protocol Jeff Garzik is working on will link a public key fingerprint to a miner sacrifice transaction. This tx could in turn be uniquely described with a short name as above. Associating this name with the public key becomes secure once the tx is sufficiently buried in the blockchain. In the identity protocol, lightweight clients check the validity of a sacrifice tx by checking that its merkle path is valid. But this path encodes, via the ordering of the hashes at each level, the location of the transaction in the block, so the lightweight client can verify the sacrifice tx's short name using only the information he already has. Some more random names: vec-halhic wom-vizpyd guv-zussof jog-copwug seg-rizges jyg-somgod pax-synjem zyg-zuxdyj gid-mutdyj rel-hyrdaj Sources of inspiration: urbit.org https://en.bitcoin.it/wiki/Identity_protocol_v1 * This is somewhat restricted: I disallowed q for obvious reasons and k because it conflicts with c, and c looks much softer and less like Klingon. H is allowed for the first consonant, but not the second, and x is allowed for the last one, but not the first one. Y is a vowel, but not a consonant. Maybe these weren't quite the right choices. Paint away! -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register > http://pubads.g.doubleclick.net/gampad/clk?id=60134791&iu=/4140/ostg.clktrk___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development
Re: [Bitcoin-development] Proposal: Vote on the blocksize limit with proof-of-stake voting
Reserving my judgement until I've though about it more (design by committee scares me, and this voting sounds expensive), I think the SPV-verifiable moving median can be done by binning the space of block size limits, and for each node in the UTXO tree, a value for each bin is stored which is the sum of the corresponding bins of each of the children. The childless nodes - which correspond to the individual UTXOs - increment the appropriate bin of their parents according to the rules you mentioned. The bin values in the root node of the UTXO tree would then be added to those, weighted appropriately, of the previous N blocks. The hash of a node would be that of the bin values, concatenated with the child nodes' hashes. In this way, any step of the calculation of the median would produce a localized error in the UTXO tree that's easily verified. The number of bins would have to be kept relatively small in order to keep this from adding too much data to the UTXO tree branches though. On Mon, Jun 10, 2013 at 2:30 AM, Peter Todd wrote: > On Mon, Jun 10, 2013 at 04:09:26AM +, John Dillon wrote: > > My general comments on the idea are that while it's hard to say if a > vote by proof-of-stake is really representative, it's likely the closest > thing we'll ever get to a fair vote. Proof-of-stake is certainely better > than just letting miners choose; as you point out miners can always > choose to decrease the blocksize anyway so we only need a vote on > allowable increases. Proof-of-stake also clearly favors those who > actually have invested in Bitcoin over those who only talk about > Bitcoin. > > I'll also say that while I know people will complain about putting > politics into a technical problem, as I keep saying, is *is* a political > issue. The limitations may be technical, but the ultimate issue is a > very political decision about what we want Bitcoin to be. Yes, there > will be people campaigning left and right to get users to vote for > various limits with their coins, deal with it. Democracy is messy. > > Voting would take a lot of the nastier politics out of the situation, > perhaps somewhat ironically. It would quite clearly take control away > from the core development team, and the Bitcoin Foundation, and put it > back in the hands of the community; you can't argue conspiracy theories > that the Foundation is trying to control Bitcoin when there is a > completely transparent voting system in place. People will complain that > big Bitcoin players are throwing their weight around, but the blockchain > itself is a voting mechanism that is anything but 1 person = 1 vote. > > Of course I wouldn't be the slightest bit surprised if users happily > vote themselves into something looking like a centralized PayPal > replacement in the long run, but at least if that happens the process by > which they get there will be transparent and relatively democratic. > > > > A vote will consist of a txout with a scriptPubKey of the following form: > > > > OP_RETURN magic vote_id txid vout vote scriptSig > > > > Where scriptSig is a valid signature for a transaction with nLockTime > > 500,000,000-1 spending txid:vout to scriptPubKey: > > > > OP_HASH160 H(OP_RETURN magic vote_id txid vout vote) OP_EQUAL > > I just wanted to point out how general this mechanism is. Regardless of > what the scriptPubKey form is, standard, P2SH, multisig, whatever to > vote is to simply prove you could have spent the txout. > > > vote_id is the ID of the specific vote being made, and magic is included > to > > allow UTXO proof implementations a as yet unspecified way of identifying > votes > > and including the weighted median as part of the UTXO tree sums. (it also > > allows SPV clients to verify the vote if the UTXO set is a Patricia tree > of > > scriptPubKeys) vote is just the numerical vote itself. > > Ah, you're assuming a direct Patricia tree. Keep in mind that > scriptPubKey's can be up to 10,000 bytes long, and an attacker can use > that (with 10,000 other txouts) to create some extremely deep trees. I > said on IRC a few days ago about how skeptical I am of implementing > consensus critical systems with such huge differences in average and > worst case, but I'll admit this is a decent use-case. > > Having said that, proof to SPV clients leaves open the interesting > possibility that a third-party holding Bitcoins on your behalf can prove > that they voted according to your wishes, or even prove they voted > according to all their users wishes. Basically we'd add a rule for the > UTXO tree where a specific OP_RETURN form is included in the UTXO tree, > even though it is unspendable, and is removed from the tree if the > master txout is spent. Note that in this case by "prove they voted" we > mean the service actually taking the step of ensuring their vote was > recorded in the blockchain. > > > The vote must compute > > the median, rather than the mean, so as to not allow someone to skew the > vote > > by simply
Re: [Bitcoin-development] Large-blocks and censorship
My views on censorship resistance in the face of scaling: 1) I expect if I'm not careful about preserving my privacy with the way I use Bitcoin, then I will always run the risk of being censored by miners. This means connecting to the network anonymously, not reusing addresses, and perhaps even mixing my coins. The onus is on me here to avoid censorship, but I'm optimistic that this privacy preservation can be made pretty automatic. 2) I expect anonymity systems to scale to accommodate Bitcoin full nodes, not Bitcoin to stay small to avoid putting pressure on anonymity systems to scale. 3) If 2 is too tall an order, then mining in a pool is always an option. There should always be some countries in the world free enough to allow mining pools to operate, and miners in countries that ban Bitcoin can simply connect to these anonymously. If not, then Bitcoin is toast anyway, is it not? If these miners are really interested in avoiding censoring transactions, then they will do their due diligence and choose a pool that doesn't do this. But even if they don't, censorship can be personally avoided by following 1. On Thu, Mar 7, 2013 at 2:19 PM, Mike Hearn wrote: > As an aside, there's a paper coming out in perhaps a few months that > describes a new way to provide Chaum-style privacy integrated with > Bitcoin, but without the use of blinding and without any need for > banks. It's quite smart, I was reviewing the paper this week. > Unfortunately the technique is too slow and too complicated to > actually integrate, but you'd probably get a kick out of it. It's > based on zero knowledge proofs. You can talk to Ian Miers if you like, > perhaps he'll send you a copy for review. > > Back on topic. > > This idea is not new. I proposed the idea of regulating miners to > freeze certain outputs two years ago: > >https://bitcointalk.org/index.php?action=printpage;topic=5979.0 > > I concluded that it was not a real risk because both mining and > transactions can be done anonymously. > > Your argument rests on the assumption that you can't mine large blocks > anonymously because Tor doesn't scale. Even if we go along with the > idea that Tor is the only way to escape regulation (it's not), you > should maybe take up its inability to move data sufficiently fast with > the developers. Given that they routinely push two gigabits/second > today, with an entirely volunteer run network, I think they'll be > surprised to learn that their project is doomed to never be usable by > miners. > > > -- > Symantec Endpoint Protection 12 positioned as A LEADER in The Forrester > Wave(TM): Endpoint Security, Q1 2013 and "remains a good choice" in the > endpoint security space. For insight on selecting the right partner to > tackle endpoint security challenges, access the full report. > http://p.sf.net/sfu/symantec-dev2dev > ___ > Bitcoin-development mailing list > Bitcoin-development@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/bitcoin-development > -- Symantec Endpoint Protection 12 positioned as A LEADER in The Forrester Wave(TM): Endpoint Security, Q1 2013 and "remains a good choice" in the endpoint security space. For insight on selecting the right partner to tackle endpoint security challenges, access the full report. http://p.sf.net/sfu/symantec-dev2dev___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development
Re: [Bitcoin-development] Enforcing inflation rules for SPV clients
Here's the conversation I had with Mike that Gregory requested a
link to:
Thanks!
Bad or hacked client devs is indeed a huge, worrying problem.
The official client is addressing this with a system called
gitian, where multiple developers all compile the same source to
the same binary and then sign the results. Multi-signatures
raise the bar for releasing hacked clients a lot. We're starting
to investigate this with bitcoinj too, but it's a lot of work.
Generally, the more people you have to involve in a
conspiracy, the less likely it is to succeed. If a few miners
started to dominate the system they have strong financial
incentives to cheat, alternatively, they may be subjected to
government pressure. Having to get the client developers
involved too makes it much harder, especially as users have to
actually upgrade.
I started a thread on the development mailing list with your
suggestion, by the way.
On Mon, Jun 25, 2012 at 1:00 AM, Daniel
Lidstrom <lidstro...@gmail.com>
wrote:
Hey Mike,
I put our conversation in the email for easy reference.
In the unlikely event of a miner conspiracy to print
money, is it really so much of a further stretch to think
the developers of a widely used client could also be
involved? (Well, maybe, since miners are unaccountable
and developers are not. OTOH if most users are
apathetic...) Also, isn't the advantage for lightweight
clients of SPV over the server-client model that you don't
have to trust any operator? Maybe I'm being too much of a
purist here...
Regarding errors being cheap to send and expensive to
verify, compartmentalizing them the way I suggested before
would make them individually cheaper to verify. Just
throwing around ideas: requiring the error message be
received by a quorum of peers before checking, and
dropping misbehaving or unreliable peers could help.
Also, not verifying error messages unless the peers
relaying them are willing to send all the data necessary
to do so would help. Hashcash could also be used to
balance the costs to send and to verify a given type of
error message. I like your idea to only check errors in
blocks that are split points, and the length of the split
could also be a consideration.
Can we move further conversations
to email please? SMF kind of sucks as an inbox.
Anyway, yes, your proposal makes a lot of sense,
although I think in practice this is unlikely to be an
issue. If a majority of miners did start mining on a
chain with new rules, even if SPV clients couldn't
detect the switch automatically it's very likely the
developers of those clients would notify the users out
of band in some way. For example, by pushing an update
to users that explains the new rules to them and tells
them how they can cash out of the Bitcoin economy if
they disagree with the new consensus.
If users are on the losing side of a rule change and
want to stay there (eg, maybe most non-miners want to
stay on the slower chain), then the client can just
checkpoint the first block after the rule change
occurred. Now even though there's a harder chain with
the new rules, the client will stay with the old rules
despite being blind to them. There's nothing that says
checkpoints have to be hard coded - clients could poll
the client developers every day to get new ones. So as
long as the SPV devs are on the ball, most users would
stay on the old rules even if the software can't do it
by itself.
All that said, broadcasting messages proving a block
broke the rules is a nice backstop if it can be done
without excessive complexity. There are some details to
think about. These messages would be cheap to create and
expensive to verify. There has to be something that
stops me claiming to SPV clients that every single block
is invalid and forcing
