Re: [Bitcoin-development] side-chains 2-way pegging (Re: is there a way to do bitcoin-staging?)
For those following this thread, we have now written a paper describing the side-chains, 2-way pegs and compact SPV proofs. (With additional authors Andrew Poelstra Andrew Miller). http://blockstream.com/sidechains.pdf Haven't seen any material discussion of this paper in this mailing list, so I'll start. (Otherwise, I've seen Peter Todd's reaction on reddit.) This paper fails to demonstrate that sidechains are anything more than a wishful thinking. It can be distilled down to this: We want such and such features, hence we'll use DMMS, the same thing Bitcoin uses, thus it will be secure! Um, no. Alt-coins also use DMMS, but aren't as secure as Bitcoin. So DMMS does not work by itself, it is a mechanism to secure a blockchain using economic incentives. The sidechains paper does not mention this, as far as I can tell. In my opinion, this is not acceptable. If you're making a proposal, you need to describe what conditions are required for it to work. Authors are clearly aware of the problem and mention it in section 6 Future directions 6.1. Hashpower attack resistance. The problem is they do not make it clear that the proposal just makes no sense until this is solved. In the discussions on reddit I've noticed that pretty much everybody believes that release of sidechains paper implies that the proposal is complete and now we are just waiting the implementation. It doesn't help that the paper itself tries to sweep the problem under the rug and has misleading statements. Particularly, I'm talking about section 4.2. Fraudulent transfers: Reorganisations of arbitrary depth are in principle possible, which could allow an attacker to completely transfer coins between sidechains before causing a reorganisation longer than the contest period on the sending chain to undo its half of the transfer. ... If the attacker is allowed to return the transferred coins to the original chain, he would increase the number of coins in his possession at the expense of other users of the sidechain. Before discussing how to handle this, we observe that this risk can be made arbitrarily small by simply increasing the contest period for transfers. Wow, really? Is this risk stochastic? The first sentence implies that attacker is able to cause a reorganization of an arbitrary depth, but the rest of the section implies that reorganizations are a naturally occurring phenomenon. All in all, I find this paper really disappointing. It's going to be influential (9 co-authors, many of which are regarded as Bitcoin core developers, must be good!) and hyped, and thus might focus research on an area which is fundamentally flawed. -- ___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development
Re: [Bitcoin-development] side-chains 2-way pegging (Re: is there a way to do bitcoin-staging?)
On Mon, Nov 3, 2014 at 1:12 PM, Alex Mizrahi alex.mizr...@gmail.com wrote:
For those following this thread, we have now written a paper
describing the side-chains, 2-way pegs and compact SPV proofs.
(With additional authors Andrew Poelstra Andrew Miller).
http://blockstream.com/sidechains.pdf
Haven't seen any material discussion of this paper in this mailing list, so
I'll start.
(Otherwise, I've seen Peter Todd's reaction on reddit.)
This paper fails to demonstrate that sidechains are anything more than a
wishful thinking.
It can be distilled down to this:
We want such and such features, hence we'll use DMMS, the same thing
Bitcoin uses, thus it will be secure!
Um, no.
Alt-coins also use DMMS, but aren't as secure as Bitcoin.
So DMMS does not work by itself, it is a mechanism to secure a blockchain
using economic incentives.
The sidechains paper does not mention this, as far as I can tell.
In my opinion, this is not acceptable. If you're making a proposal, you need
to describe what conditions are required for it to work.
From the introduction [...]Because signers prove computational work,
rather than proving secret knowledge as
is typical for digital signatures, we refer to them as miners. To
achieve stable consensus on the
blockchain history, economic incentives are provided where miners are
rewarded with fees and
subsidies in the form of coins that are valuable only if the miners
form a shared valid history,
incentivising them to behave honestly.[...]
Ignoring altrustic miners, the irreversibility of a DMMS chain
obviously depends on the rewards received by miners on that chain.
Nobody is claiming that sidechains will be as secure bitcoin, any 2
way pegged assets is always more secure (probably too vague of a
term in this context) in its original chain.
Authors are clearly aware of the problem and mention it in section 6 Future
directions 6.1. Hashpower attack resistance.
The problem is they do not make it clear that the proposal just makes no
sense until this is solved.
Since all seigniorage from Bitcoin's initial distribution is spent on
mining subsidies for the main chain, it is not available to subsidize
sidechains too. Thus sidechains, in principle, reward their miners
with the same Bitcoin will use in the future: only transaction fees.
Since some people claim that won't be enough (is not always clear to
me if they believe that won't be enough for sidechains or also for
bitcoin when the subsidies are gone), we included this section with
other ideas we have explored to further. Some of them, like
time-shifted fees could be interesting for Bitcoin itself in the
future.
It doesn't help that the paper itself tries to sweep the problem under the
rug and has misleading statements.
Particularly, I'm talking about section 4.2. Fraudulent transfers:
Reorganisations of arbitrary depth are in principle possible, which could
allow an attacker to
completely transfer coins between sidechains before causing a reorganisation
longer than the contest
period on the sending chain to undo its half of the transfer. ... If the
attacker is allowed to return the transferred coins to the original
chain, he would increase the number of coins in his possession at the
expense of other users of the sidechain.
Before discussing how to handle this, we observe that this risk can be made
arbitrarily small by
simply increasing the contest period for transfers.
Wow, really? Is this risk stochastic?
The first sentence implies that attacker is able to cause a reorganization
of an arbitrary depth, but the rest of the section implies that
reorganizations are a naturally occurring phenomenon.
Reorganizations are both a naturally occurring phenomenon and
something that an attacker may cause to revert history.
Section 11. Calculations of the Bitcoin whitepaper gives you this
formula (in C code):
#include math.h
double AttackerSuccessProbability(double q, int z)
{
double p = 1.0 - q;
double lambda = z * (q / p);
double sum = 1.0;
int i, k;
for (k = 0; k = z; k++)
{
double poisson = exp(-lambda);
for (i = 1; i = k; i++)
poisson *= lambda / i;
sum -= poisson * (1 - pow(q / p, z - k));
}
return sum;
}
Also says Given our assumption that p q, the probability drops
exponentially as the number of blocks the
attacker has to catch up with increases.
In this case, the contest period determines z, the number of blocks
the attacker has to catch up from the honest chain.
So the longer the contest period is, the harder it is to succeed with
a fraudulent transfer.
For example, if a given sidechain chooses 52560 as the contest period
(1 year assuming 10 min blocks), it will be very hard for an attacker
to produce a fake alternative longest-than-the-last-year-of-history
fork to steal coins.
A sidechain with such an extreme contest period would probably not be
very practical though, since honest users would have to wait more than
Re: [Bitcoin-development] side-chains 2-way pegging (Re: is there a way to do bitcoin-staging?)
From the introduction [...]Because signers prove computational work, rather than proving secret knowledge as is typical for digital signatures, we refer to them as miners. To achieve stable consensus on the blockchain history, economic incentives are provided where miners are rewarded with fees and subsidies in the form of coins that are valuable only if the miners form a shared valid history, incentivising them to behave honestly.[...] This isn't applicable in case of sidechains: anybody with sufficient hashpower will be able to unlock a locked coin on the parent chain by producing an SPV proof. Only if the miners form a shared valid history isn't a requirement here, as miner will get bitcoins which aren't in any way connect to sidechain he have wrecked. Thus there is no incentive to behave honestly. Thus sidechains, in principle, reward their miners with the same Bitcoin will use in the future: only transaction fees. Since some people claim that won't be enough Whether it is enough depends on a variety of factors, including existence of other chains miner can mine. You cannot assume that it is the same situation as with a simple single-chain model. E.g. imagine 1000 BTC were moved to a sidechain. Miners can keep mining bitcoins as usual, and in parallel work on an SPV proof to claim these 1000 BTC. (I assume that merged-mining is allowed.) In this case the amount of fees which miners could collect by honest mining on the sidechain is irrelevant, as long as it is smaller than 1000 BTC. This is quite different from attacks which can be performed on vanilla Bitcoin (see below), so I don't think you can say that the security model is the same. Also says Given our assumption that p q, the probability drops exponentially as the number of blocks the attacker has to catch up with increases. Yes, but that doesn't apply to reorganizations which attacker might cause intentionally. Hence I think it was disingenuous to include these two very different treats into one section: it sounds like you claim that attacker-induced reorganizations are unlikely, while it isn't the case. So the longer the contest period is, the harder it is to succeed with a fraudulent transfer. Yes, but harder isn't same as unlikely. Another problem with this section is that it only mentions reorganizations. But a fraudulent transfer can happen without a reorganization, as an attacker can produce an SPV proof which is totally fake. So this is not similar to double-spending, attacker doesn't need to own coins to perform an attack. I hope this clarifies our assumptions. Yep, thanks. It looks like you assume that sidechain security will be similar to Bitcoin security in the long term. Now quite the assumptions I've been looking for, but OK... I'm sorry for the harsh tone, but I just find it hilarious that people who explained that proof-of-stake is not going to work because an attacker might collect everybody's past signing keys to rewrite the whole history (I'm referring to this: https://download.wpsoftware.net/bitcoin/pos.pdf ) didn't bother to mention that miners can collude to wreck a sidechain and get an awesome reward, basically for free. something something the mote in thy brother's eye something something -- ___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development
Re: [Bitcoin-development] side-chains 2-way pegging (Re: is there a way to do bitcoin-staging?)
On Mon, Nov 3, 2014 at 5:01 PM, Alex Mizrahi alex.mizr...@gmail.com wrote: This isn't applicable in case of sidechains: anybody with sufficient hashpower will be able to unlock a locked coin on the parent chain by producing an SPV proof. Only if the miners form a shared valid history isn't a requirement here, as miner will get bitcoins which aren't in any way connect to sidechain he have wrecked. Thus there is no incentive to behave honestly. But if the majority of the sidechain miners keep working on the honest chain, anyone can submit a reorg proof during the contest period that invalidates this unlockment on the parent chain. Honest sidechain miners will get rewarded in the sidechain, and those rewards will only be valuable if they form a shared valid history. Whether it is enough depends on a variety of factors, including existence of other chains miner can mine. You cannot assume that it is the same situation as with a simple single-chain model. This is correct. There's many variables at play. E.g. imagine 1000 BTC were moved to a sidechain. Miners can keep mining bitcoins as usual, and in parallel work on an SPV proof to claim these 1000 BTC. (I assume that merged-mining is allowed.) In this case the amount of fees which miners could collect by honest mining on the sidechain is irrelevant, as long as it is smaller than 1000 BTC. As explained many times, sidechains and merged mining are orthogonal: pegged sidechains don't need to use merged mining just as merged mining altchains don't need to be sidechains. Anyway, I think you're somehow assuming that deciding to mine against the sidechain instead of mining for its rewards. This is simply not true. No matter how big the attack incentive is, if you're assuming my 52560 contest period example and that the attacker doesn't control the majority of the hashing power on the sidechain, the probability of achieving a one-year reorg is negligible. In the meantime honest nodes are getting some reward, let's say 0.1 BTC per block. That's 5256 btc/year to the honest nodes vs 0 btc/year for the attacker. If the attacker controls, say, 10% of the network, he's losing 525.6 btc/year in opportunity costs for an extremely small chance of getting 1000 btc. This is quite different from attacks which can be performed on vanilla Bitcoin (see below), so I don't think you can say that the security model is the same. We're not claiming that the security model is the same, we just compare it to Bitcoin's because it's similar in many senses. Also says Given our assumption that p q, the probability drops exponentially as the number of blocks the attacker has to catch up with increases. Yes, but that doesn't apply to reorganizations which attacker might cause intentionally. Yes, that's precisely the kind of reorganizations the BITCOIN WHITEPAPER is talking about in section 11 Calculations: reorganizations caused intentionally by an attacker. Please read it again. q_z = probability THE ATTACKER will ever catch up from z blocks behind. Hence I think it was disingenuous to include these two very different treats into one section: it sounds like you claim that attacker-induced reorganizations are unlikely, while it isn't the case. If it sounds to you like we're claiming that attacker-induced reorganizations are not likely, maybe we could have expressed it some other way. That was certainly not the intention. That's not true for Bitcoin itself and that's not what we're claiming. So the longer the contest period is, the harder it is to succeed with a fraudulent transfer. Yes, but harder isn't same as unlikely. Exponentially harder with the number of blocks is good enough for me. Another problem with this section is that it only mentions reorganizations. But a fraudulent transfer can happen without a reorganization, as an attacker can produce an SPV proof which is totally fake. So this is not similar to double-spending, attacker doesn't need to own coins to perform an attack. That would be a reorganization too, you can't create a completely fake history for a sidechain, the attacker will share some of the chain's history. Yes, the attacker can create an SPV proof of a fake chain and in that sense, this is different from a regular double-spend. If honest miners control the majority of the hashing power, they will produce a valid chain longer than the fake chain. And then anyone can use that reorg proof to stop the attacker before the contest period. You see, SPV security is not the same as SPV security with more than 52560 confirmations of the transaction I'm receiving. I hope this clarifies our assumptions. Yep, thanks. It looks like you assume that sidechain security will be similar to Bitcoin security in the long term. Now quite the assumptions I've been looking for, but OK... I'm sorry for the harsh tone, but I just find it hilarious that people who explained that proof-of-stake is not going to work because an
Re: [Bitcoin-development] side-chains 2-way pegging (Re: is there a way to do bitcoin-staging?)
On Mon, Nov 03, 2014 at 06:01:46PM +0200, Alex Mizrahi wrote: Yes, but harder isn't same as unlikely. We are aware of the distintion between hardness (expected work) and likelihood of successful attack -- much of Appendix B talks about this, in the context of producing compact SPV proofs which are (a) hard to forge, and (b) very unlikely to be forgeries. We did spend some time formalizing this but due to space constraints (and it being somewhat beside the point of the whitepaper beyond we believe it is possible to do), we did not explore this in as great depth as we'd have liked. Another problem with this section is that it only mentions reorganizations. But a fraudulent transfer can happen without a reorganization, as an attacker can produce an SPV proof which is totally fake. So this is not similar to double-spending, attacker doesn't need to own coins to perform an attack. Well, even in the absense of a reorganization, the attacker's false proof will just be invalidated by a proof of longer work on the real chain. And there is still a real cost to producing the false proof. -- Andrew Poelstra Mathematics Department, University of Texas at Austin Email: apoelstra at wpsoftware.net Web: http://www.wpsoftware.net/andrew pgpHV90RFPrEv.pgp Description: PGP signature -- ___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development
Re: [Bitcoin-development] side-chains 2-way pegging (Re: is there a way to do bitcoin-staging?)
-BEGIN PGP SIGNED MESSAGE- Hash: SHA512 Possibly relevant... https://www.iacr.org/archive/eurocrypt2002/23320001/euro02.ps Some interesting stuff here too http://des.cse.nsysu.edu.tw/asiacrypt2014/accepted/index.htm Andrew Poelstra wrote: false proof - -- http://abis.io ~ a protocol concept to enable decentralization and expansion of a giving economy, and a new social good https://keybase.io/odinn -BEGIN PGP SIGNATURE- iQEcBAEBCgAGBQJUV9mzAAoJEGxwq/inSG8C0qwIAJZdOmeSK7pIw2KTj0lQlPIp MIc1w2KL+qIVXSrlqyNlcIhlW4gK+/cuYD+PZ7wSGHV2k9OD6AcOo3JfGYgk4LP/ 3GIrY/+TQVoTRKVgTGvR2uqUILuwCPTtr/7Uy2s2y2mveyFda6ZA7sMeoeiTsQQe 9aPS6tLK0W7g+gbqM2QwC3G521iPJ9RE9JOsxCVxGplVUuOLpPzovQjFO3MKYdeu eBq5ORr4ICvphk+yVygkQvw/AuYZjqTuKEjRfK0v5EryZM9Qsj/1pEhYAH8tdLrV 4NB5lDXIo3rt58wPqyeacMF6WW2LShb1VDl6Hnvi35GXURpBgxXM/N4pO+l444k= =9q9h -END PGP SIGNATURE- -- ___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development
Re: [Bitcoin-development] side-chains 2-way pegging (Re: is there a way to do bitcoin-staging?)
On 22 October 2014 23:54, Adam Back a...@cypherspace.org wrote: For those following this thread, we have now written a paper describing the side-chains, 2-way pegs and compact SPV proofs. (With additional authors Andrew Poelstra Andrew Miller). http://blockstream.com/sidechains.pdf A very well written paper, thank you for putting it together and sharing. Given it's the 6 year birthday of satoshi's white paper, I just read through it again. I find it interesting that bitcoin is never defined in Satoshi's paper, indeed, it never appears after the first word. The term Electronic Coin is defined. The terminology of bitcoin / altcoin / altchain / blockchain in this paper still leaves me slightly uneasy, and I try to use the terms electronic coin and electronic cash, more often. If satoshi were to come back and continue his work, would it be an altcoin, would it be The blockchain, would it be bitcoin, or would what we know as bitcoin become an alt. I suspect these questions are nothing more than academic curiosity. But I think I'll get more used to it over time :) In any case, happy birthday bitcoin :) Adam On 16 March 2014 15:58, Adam Back a...@cypherspace.org wrote: So an update on 1-way pegging (aka bitcoin staging, explained in quoted text at bottom): it turns out secure 2-way pegging is also possible (with some bitcoin change to help support it). The interesting thing is this allows interoperability in terms of being able to move bitcoin into and out of a side chain. The side chains may have some different parameters, or experimental things people might want to come up with (subject to some minimum compatibility at the level of being able to produce an SPV proof of a given form). At the time of the 1-way peg discussion I considered 2-way peg as desirable and it seemed plausible with bitcoin changes, but the motivation for 1-way peg was to make it less risky to make changes on bitcoin, so that seemed like a catch-22 loop. Also in the 2-way peg thought experiment I had not realized how simple it was to still impose a security firewall in the 2-way peg also. So Greg Maxwell proposed in Dec last year a practically compact way to do 2-way pegging using SPV proofs. And also provided a simple argument of how this can provide a security firewall. (Security firewall means the impact of security bugs on the side-chain is limited to the people with coins in it; bitcoin holders who did not use it are unaffected). [1] How it works: 1. to maintain the 21m coins promise, you start a side-chain with no in-chain mining subsidy, all bitcoin creation happens on bitcoin chain (as with 1-way peg). Reach a reasonable hash rate. (Other semantics than 1:1 peg should be possible, but this is the base case). 2. you move coins to the side-chain by spending them to a fancy script, which suspends them, and allows them to be reanimated by the production of an SPV proof of burn on the side-chain. 3. the side-chain has no mining reward, but it allows you to mint coins at no mining cost by providing an SPV proof that the coin has been suspended as in 2 on bitcoin. The SPV proof must be buried significantly before being used to reduce risk of reorganization. The side-chain is an SPV client to the bitcoin network, and so maintains a view of the bitcoin hash chain (but not the block data). 4. the bitcoin chain is firewalled from security bugs on the side chain, because bitcoin imposes the rule that no more coins can be reanimated than are currently suspend (with respect to a given chain). 5. to simplify what they hypothetical bitcoin change would need to consider and understand, after a coin is reanimated there is a maturity period imposed (say same as fresh mined coins). During the maturity period the reanimation script allows a fraud proof to spend the coins back. A fraud bounty fee (equal to the reanimate fee) can be offered by the mover to incentivize side-chain full nodes to watch reanimations and search for fraud proofs. 6. a fraud proof is an SPV proof with a longer chain showing that the proof of burn was orphaned. There are a few options to compress the SPV proof, via Fiat-Shamir transform to provide a compact proof of amount work contained in a merkle tree of proofs of work (as proposed by Fabien Coelho link on http://hashcash.org/papers/) with params like 90% of work is proven. But better is something Greg proposed based on skip-lists organized in a tree, where 'lucky' proofs of work are used to skip back further. (Recalling that if you search for a 64-bit leading-0 proof-of-work, half the time you get a 65-bit, quarter 66-bit etc.) With this mechanism you can accurately prove the amount of proof of work in a compressed tree (rather than ~90%). Apart from pegging from bitcoin to a side-chain, if a private chain is made with same rules
Re: [Bitcoin-development] side-chains 2-way pegging (Re: is there a way to do bitcoin-staging?)
For those following this thread, we have now written a paper describing the side-chains, 2-way pegs and compact SPV proofs. (With additional authors Andrew Poelstra Andrew Miller). http://blockstream.com/sidechains.pdf Adam On 16 March 2014 15:58, Adam Back a...@cypherspace.org wrote: So an update on 1-way pegging (aka bitcoin staging, explained in quoted text at bottom): it turns out secure 2-way pegging is also possible (with some bitcoin change to help support it). The interesting thing is this allows interoperability in terms of being able to move bitcoin into and out of a side chain. The side chains may have some different parameters, or experimental things people might want to come up with (subject to some minimum compatibility at the level of being able to produce an SPV proof of a given form). At the time of the 1-way peg discussion I considered 2-way peg as desirable and it seemed plausible with bitcoin changes, but the motivation for 1-way peg was to make it less risky to make changes on bitcoin, so that seemed like a catch-22 loop. Also in the 2-way peg thought experiment I had not realized how simple it was to still impose a security firewall in the 2-way peg also. So Greg Maxwell proposed in Dec last year a practically compact way to do 2-way pegging using SPV proofs. And also provided a simple argument of how this can provide a security firewall. (Security firewall means the impact of security bugs on the side-chain is limited to the people with coins in it; bitcoin holders who did not use it are unaffected). [1] How it works: 1. to maintain the 21m coins promise, you start a side-chain with no in-chain mining subsidy, all bitcoin creation happens on bitcoin chain (as with 1-way peg). Reach a reasonable hash rate. (Other semantics than 1:1 peg should be possible, but this is the base case). 2. you move coins to the side-chain by spending them to a fancy script, which suspends them, and allows them to be reanimated by the production of an SPV proof of burn on the side-chain. 3. the side-chain has no mining reward, but it allows you to mint coins at no mining cost by providing an SPV proof that the coin has been suspended as in 2 on bitcoin. The SPV proof must be buried significantly before being used to reduce risk of reorganization. The side-chain is an SPV client to the bitcoin network, and so maintains a view of the bitcoin hash chain (but not the block data). 4. the bitcoin chain is firewalled from security bugs on the side chain, because bitcoin imposes the rule that no more coins can be reanimated than are currently suspend (with respect to a given chain). 5. to simplify what they hypothetical bitcoin change would need to consider and understand, after a coin is reanimated there is a maturity period imposed (say same as fresh mined coins). During the maturity period the reanimation script allows a fraud proof to spend the coins back. A fraud bounty fee (equal to the reanimate fee) can be offered by the mover to incentivize side-chain full nodes to watch reanimations and search for fraud proofs. 6. a fraud proof is an SPV proof with a longer chain showing that the proof of burn was orphaned. There are a few options to compress the SPV proof, via Fiat-Shamir transform to provide a compact proof of amount work contained in a merkle tree of proofs of work (as proposed by Fabien Coelho link on http://hashcash.org/papers/) with params like 90% of work is proven. But better is something Greg proposed based on skip-lists organized in a tree, where 'lucky' proofs of work are used to skip back further. (Recalling that if you search for a 64-bit leading-0 proof-of-work, half the time you get a 65-bit, quarter 66-bit etc.) With this mechanism you can accurately prove the amount of proof of work in a compressed tree (rather than ~90%). Apart from pegging from bitcoin to a side-chain, if a private chain is made with same rules to the side-chain it becomes possible with some modifications to the above algorithm to peg the side-chain to a private chain. Private chain meaning a chain with the same format but signature of single server in place of hashing, and timestamping of the block signatures in the mined side chain. And then reactive security on top of that by full nodes/auditors trying to find fraud proofs (rewrites of history relative to side-chain mined time-stamp or approved double-spends). The reaction is to publish a fraud proof and move coins back to the side chain, and then regroup on a new server. (Open transactions has this audit + reactive model but as far as I know does it via escrow, eg the voting pools for k of n escrow of the assets on the private server.) I also proposed the same reactive audit model but for auditable namespaces [4]. Private chains add some possiblity for higher scaling, while retaining bitcoin security properties. (You need to add the ability for a user to
Re: [Bitcoin-development] side-chains 2-way pegging (Re: is there a way to do bitcoin-staging?)
I've already added it here: http://www.opencryptocurrencyreview.com/papers/123/enabling-blockchain-innovations-with-pegged-sidechains I made this site to allow discussions on exactly these sorts of things to be publicly visible and easily discoverable in the future (this is why I replied to all). Please let me know what you think of the site. Daniel p.s. I'm not trying to monetize this site. I just tried to make something I thought could be useful. On Wed, Oct 22, 2014 at 10:54 PM, Adam Back a...@cypherspace.org wrote: For those following this thread, we have now written a paper describing the side-chains, 2-way pegs and compact SPV proofs. (With additional authors Andrew Poelstra Andrew Miller). http://blockstream.com/sidechains.pdf Adam On 16 March 2014 15:58, Adam Back a...@cypherspace.org wrote: So an update on 1-way pegging (aka bitcoin staging, explained in quoted text at bottom): it turns out secure 2-way pegging is also possible (with some bitcoin change to help support it). The interesting thing is this allows interoperability in terms of being able to move bitcoin into and out of a side chain. The side chains may have some different parameters, or experimental things people might want to come up with (subject to some minimum compatibility at the level of being able to produce an SPV proof of a given form). At the time of the 1-way peg discussion I considered 2-way peg as desirable and it seemed plausible with bitcoin changes, but the motivation for 1-way peg was to make it less risky to make changes on bitcoin, so that seemed like a catch-22 loop. Also in the 2-way peg thought experiment I had not realized how simple it was to still impose a security firewall in the 2-way peg also. So Greg Maxwell proposed in Dec last year a practically compact way to do 2-way pegging using SPV proofs. And also provided a simple argument of how this can provide a security firewall. (Security firewall means the impact of security bugs on the side-chain is limited to the people with coins in it; bitcoin holders who did not use it are unaffected). [1] How it works: 1. to maintain the 21m coins promise, you start a side-chain with no in-chain mining subsidy, all bitcoin creation happens on bitcoin chain (as with 1-way peg). Reach a reasonable hash rate. (Other semantics than 1:1 peg should be possible, but this is the base case). 2. you move coins to the side-chain by spending them to a fancy script, which suspends them, and allows them to be reanimated by the production of an SPV proof of burn on the side-chain. 3. the side-chain has no mining reward, but it allows you to mint coins at no mining cost by providing an SPV proof that the coin has been suspended as in 2 on bitcoin. The SPV proof must be buried significantly before being used to reduce risk of reorganization. The side-chain is an SPV client to the bitcoin network, and so maintains a view of the bitcoin hash chain (but not the block data). 4. the bitcoin chain is firewalled from security bugs on the side chain, because bitcoin imposes the rule that no more coins can be reanimated than are currently suspend (with respect to a given chain). 5. to simplify what they hypothetical bitcoin change would need to consider and understand, after a coin is reanimated there is a maturity period imposed (say same as fresh mined coins). During the maturity period the reanimation script allows a fraud proof to spend the coins back. A fraud bounty fee (equal to the reanimate fee) can be offered by the mover to incentivize side-chain full nodes to watch reanimations and search for fraud proofs. 6. a fraud proof is an SPV proof with a longer chain showing that the proof of burn was orphaned. There are a few options to compress the SPV proof, via Fiat-Shamir transform to provide a compact proof of amount work contained in a merkle tree of proofs of work (as proposed by Fabien Coelho link on http://hashcash.org/papers/) with params like 90% of work is proven. But better is something Greg proposed based on skip-lists organized in a tree, where 'lucky' proofs of work are used to skip back further. (Recalling that if you search for a 64-bit leading-0 proof-of-work, half the time you get a 65-bit, quarter 66-bit etc.) With this mechanism you can accurately prove the amount of proof of work in a compressed tree (rather than ~90%). Apart from pegging from bitcoin to a side-chain, if a private chain is made with same rules to the side-chain it becomes possible with some modifications to the above algorithm to peg the side-chain to a private chain. Private chain meaning a chain with the same format but signature of single server in place of hashing, and timestamping of the block signatures in the mined side chain. And then reactive security on top of that by full nodes/auditors trying to find fraud proofs (rewrites of history relative to side-chain mined time-stamp or approved
Re: [Bitcoin-development] side-chains 2-way pegging (Re: is there a way to do bitcoin-staging?)
Sorry Bryan, this was the first paper posted to this list since I've been on it that I added to my site. I was quite excited about this. I was not planning on and certainly won't be making this advertisement after every paper posted on this list (I may do it on reddit). I did post on reddit a few times yes, but I assumed that this list's user base didn't overlap extremely (does it?). I'm not sure why my posts got down voted there. The down voters gave me no constructive feedback about the usefulness of my site, and neither have you. Are you able to give me your feedback on the site I've spent quite some time setting up privately so that we don't spam this list again? On Wed, Oct 22, 2014 at 11:35 PM, Bryan Bishop kanz...@gmail.com wrote: On Wed, Oct 22, 2014 at 5:01 PM, Daniel Murrell dsmurr...@gmail.com wrote: p.s. I'm not trying to monetize this site. I just tried to make something I thought could be useful. [Unsolicited administrivia follows.] You have been posting this in a bunch of places for a while now, at least three times today by my count on other mediums. I also observed negative karma scores associated with these posts. Maybe you could consider toning down the message frequency? I think by now everyone knows you want them to use your site. I also think that in the limit that it would be inappropriate for /everyone/ to post all possible research sites, or even vaguely topical discussion sites, for every paper posted. Personally, I would much rather have discussions happen on the mailing list anyway, although if I had a different opinion I certainly hope I would still send this message. Thank you. - Bryan http://heybryan.org/ 1 512 203 0507 -- ___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development
Re: [Bitcoin-development] side-chains 2-way pegging (Re: is there a way to do bitcoin-staging?)
Take the discussion of this site to another M-L, please. It is off-topic. Actual discussion of the paper and side-chains is on-topic. This M-L is publicly archived. On Wed, Oct 22, 2014 at 6:52 PM, Daniel Murrell dsmurr...@gmail.com wrote: Sorry Bryan, this was the first paper posted to this list since I've been on it that I added to my site. I was quite excited about this. I was not planning on and certainly won't be making this advertisement after every paper posted on this list (I may do it on reddit). I did post on reddit a few times yes, but I assumed that this list's user base didn't overlap extremely (does it?). I'm not sure why my posts got down voted there. The down voters gave me no constructive feedback about the usefulness of my site, and neither have you. Are you able to give me your feedback on the site I've spent quite some time setting up privately so that we don't spam this list again? On Wed, Oct 22, 2014 at 11:35 PM, Bryan Bishop kanz...@gmail.com wrote: On Wed, Oct 22, 2014 at 5:01 PM, Daniel Murrell dsmurr...@gmail.com wrote: p.s. I'm not trying to monetize this site. I just tried to make something I thought could be useful. [Unsolicited administrivia follows.] You have been posting this in a bunch of places for a while now, at least three times today by my count on other mediums. I also observed negative karma scores associated with these posts. Maybe you could consider toning down the message frequency? I think by now everyone knows you want them to use your site. I also think that in the limit that it would be inappropriate for /everyone/ to post all possible research sites, or even vaguely topical discussion sites, for every paper posted. Personally, I would much rather have discussions happen on the mailing list anyway, although if I had a different opinion I certainly hope I would still send this message. Thank you. - Bryan http://heybryan.org/ 1 512 203 0507 -- ___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development -- Jeff Garzik Bitcoin core developer and open source evangelist BitPay, Inc. https://bitpay.com/ -- ___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development
