Re: [Bitcoin-development] Proposal: Vote on the blocksize limit with proof-of-stake voting

2013-06-28 Thread John Dillon
-BEGIN PGP SIGNED MESSAGE-
Hash: SHA256

 Thinking about this a little more, I guess it does not hurt to build some
 kind of voting system into the clients.  But I think it's more useful for
 straw polls.  For example a bug fix 100% of people should agree on.  A
 protocol optimization perhaps 80% would agree on.  A protocol change that
 redistributes wealth or incentives perhaps only 60% will agree on.

 At this point in time it's far too easy to deliver contentious changes into
 the hands of the general population.  I think that fortunately we're blessed
 with a very strong dev team, but the fundamental philosophy of bitcoin is to
 not put too much trust in single point, but rather, to distribute and
 diversify trust to the edges.

I disagree entirely. Your example of straw polls for bug fixes and
features is precisely what the current method of rough consensus and
running code, an IETF expression, handles just fine.

What the method does not handle effectively are issues that are
fundementally political rather than technical in nature. Blocksize is
precisely the latter because while the tradeoffs are technical in
nature the fundemental issue at hand is what do we want Bitcoin to be?
Who are we going to allow to participate?
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Re: [Bitcoin-development] Proposal: Vote on the blocksize limit with proof-of-stake voting

2013-06-22 Thread Melvin Carvalho
On 10 June 2013 06:09, John Dillon john.dillon...@googlemail.com wrote:

 -BEGIN PGP SIGNED MESSAGE-
 Hash: SHA256

 It has been suggested that we leave the decision of what the blocksize to
 be
 entirely up to miners. However this leaves a parameter that affects every
 Bitcoin participant in the control of a small minority. Of course we can
 not
 force miners to increase the blocksize if they choose to decrease it,
 because
 the contents of the blocks they make are their decision and their decision
 only. However proposals to leave the maximum size unlimited to allow
 miners to
 force us to accept arbitrarily large blocks even if the will of the
 majority of
 Bitcoin participants is that they wish to remain able to validate the
 blockchain.

 What we need is a way to balance this asymetrical power relationship.

 Proof-of-stake voting gives us a way of achieving that balance.
 Essentially for
 a miner to prove that the majority will of the poeple is to accept a larger
 blocksize they must prove that the majority has in fact voted for that
 increase. The upper limit on the blocksize is then determined by the
 median of
 all votes, where each txout in the UTXO set is one vote, weighted by txout
 value. A txout without a corresponding vote is considered to be a vote for
 the
 status quo. To allow the voting process to continue even if coins are
 lost
 votes, including default votes, are weighted inversely according to their
 age
 in years after 1 year. IE a vote with weight 1BTC that is 1.5 years old
 will be
 recorded the same as a 1 year old vote weighted as 0.67BTC, and a 1 day
 old
 and 6 months old UTXO are treated equivalently. The 1 year minimum is
 simply to
 make voting required no more than once per year. (of course, a real
 implementation should do all of these figures by block height, IE after
 52,560
 blocks instead of after 1 year)

 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

 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. The vote must
 compute
 the median, rather than the mean, so as to not allow someone to skew the
 vote
 by simply setting their value extremely high. Someone who still remembers
 their
 statistics classes should chime in on the right way to compute a median in
 a
 merkle-sum-tree.

 The slightly unusual construction of votes makes implementation by wallet
 software as simple as possible within existing code-paths. Votes could
 still be
 constructed even in wallets lacking specific voting capability provided the
 wallet software does have the ability to set nLockTime.

 Of course in the future the voting mechanism can be used for additional
 votes
 with an additional vote_id. For instance the Bitcoin community could vote
 to
 increase the inflation subsidy, another example of a situation where the
 wishes
 of miners may conflict with the wishes of the broader community.

 Users may of course actually create these specially encoded txouts
 themselves
 and get them into the blockchain.  However doing so is not needed as a
 given
 vote is only required to actually be in the chain by a miner wishing to
 increase the blocksize. Thus we should extend the P2P protocol with a
 mechanism
 by which votes can be broadcast independently of transactions. To prevent
 DoS
 attacks only votes with known vote_id's will be accepted, and only for
 txid:vout's already in the blockchain, and a record of txouts for whom
 votes
 have already broadcast will be kept. (this record need not be
 authoritative as
 its purpose is only to prevent DoS attacks) Miners wishing to increase the
 blocksize can record these votes and include them in the blocks they mine
 as
 required. To reduce the cost of including votes in blocks 5% of every block
 should be assigned to voting only. (this can be implemented by a soft-fork)

 For any given block actual limit in effect is then the rolling median of
 the
 blocks in the last year. At the beginning of every year the value
 considered to
 be the status quo resets to the mean of the limit at the beginning and end
 of
 the interval.  (again, by year we really mean 52,560 blocks) The rolling
 median and periodic reset process ensures that the limit changes gradually
 and
 is not influenced by temporary events such as hacks to large exchanges or
 malicious wallet software.  The rolling median also ensures that for a
 miner
 the act of including a vote is never wasted due to the 

Re: [Bitcoin-development] Proposal: Vote on the blocksize limit with proof-of-stake voting

2013-06-15 Thread John Dillon
-BEGIN PGP SIGNED MESSAGE-
Hash: SHA256

On Mon, Jun 10, 2013 at 5:43 PM, Peter Todd p...@petertodd.org wrote:
 On Mon, Jun 10, 2013 at 01:25:05PM -0400, Alan Reiner wrote:
 to sign votes.  Not only that, but it would require them to reveal their
 public key, which while isn't technically so terrible, large amounts of
 money intended to be kept in storage for 10+ years will prefer to avoid
 any exposure at all, in the oft-chance that QCs come around a lot
 earlier than we expected.  Sure, the actual risk should be pretty much
 non-existent, but some of the most paranoid folks are probably the same
 ones who have a lot of funds and want 100.00% of the security that is
 possible.   They will see this as wildly inconvenient.

 Solving that problem is pretty easy actually: just add a voting only
 public key to your outputs. Specifically you would have an opcode called
 something like OP_VOTE and put a code-path in your script that only
 executes for that specific key.

Rather than OP_VOTE all you really need is the spending tx matches a
template functionality that has been proposed for many other things.
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Re: [Bitcoin-development] Proposal: Vote on the blocksize limit with proof-of-stake voting

2013-06-10 Thread Daniel Lidstrom
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 p...@petertodd.org 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 setting their value extremely high. Someone who still
 remembers their
  

Re: [Bitcoin-development] Proposal: Vote on the blocksize limit with proof-of-stake voting

2013-06-10 Thread Melvin Carvalho
On 10 June 2013 06:09, John Dillon john.dillon...@googlemail.com wrote:

 -BEGIN PGP SIGNED MESSAGE-
 Hash: SHA256

 It has been suggested that we leave the decision of what the blocksize to
 be
 entirely up to miners. However this leaves a parameter that affects every
 Bitcoin participant in the control of a small minority. Of course we can
 not
 force miners to increase the blocksize if they choose to decrease it,
 because
 the contents of the blocks they make are their decision and their decision
 only. However proposals to leave the maximum size unlimited to allow
 miners to
 force us to accept arbitrarily large blocks even if the will of the
 majority of
 Bitcoin participants is that they wish to remain able to validate the
 blockchain.

 What we need is a way to balance this asymetrical power relationship.

 Proof-of-stake voting gives us a way of achieving that balance.
 Essentially for
 a miner to prove that the majority will of the poeple is to accept a larger
 blocksize they must prove that the majority has in fact voted for that
 increase. The upper limit on the blocksize is then determined by the
 median of
 all votes, where each txout in the UTXO set is one vote, weighted by txout
 value. A txout without a corresponding vote is considered to be a vote for
 the
 status quo. To allow the voting process to continue even if coins are
 lost
 votes, including default votes, are weighted inversely according to their
 age
 in years after 1 year. IE a vote with weight 1BTC that is 1.5 years old
 will be
 recorded the same as a 1 year old vote weighted as 0.67BTC, and a 1 day
 old
 and 6 months old UTXO are treated equivalently. The 1 year minimum is
 simply to
 make voting required no more than once per year. (of course, a real
 implementation should do all of these figures by block height, IE after
 52,560
 blocks instead of after 1 year)

 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

 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. The vote must
 compute
 the median, rather than the mean, so as to not allow someone to skew the
 vote
 by simply setting their value extremely high. Someone who still remembers
 their
 statistics classes should chime in on the right way to compute a median in
 a
 merkle-sum-tree.

 The slightly unusual construction of votes makes implementation by wallet
 software as simple as possible within existing code-paths. Votes could
 still be
 constructed even in wallets lacking specific voting capability provided the
 wallet software does have the ability to set nLockTime.

 Of course in the future the voting mechanism can be used for additional
 votes
 with an additional vote_id. For instance the Bitcoin community could vote
 to
 increase the inflation subsidy, another example of a situation where the
 wishes
 of miners may conflict with the wishes of the broader community.

 Users may of course actually create these specially encoded txouts
 themselves
 and get them into the blockchain.  However doing so is not needed as a
 given
 vote is only required to actually be in the chain by a miner wishing to
 increase the blocksize. Thus we should extend the P2P protocol with a
 mechanism
 by which votes can be broadcast independently of transactions. To prevent
 DoS
 attacks only votes with known vote_id's will be accepted, and only for
 txid:vout's already in the blockchain, and a record of txouts for whom
 votes
 have already broadcast will be kept. (this record need not be
 authoritative as
 its purpose is only to prevent DoS attacks) Miners wishing to increase the
 blocksize can record these votes and include them in the blocks they mine
 as
 required. To reduce the cost of including votes in blocks 5% of every block
 should be assigned to voting only. (this can be implemented by a soft-fork)

 For any given block actual limit in effect is then the rolling median of
 the
 blocks in the last year. At the beginning of every year the value
 considered to
 be the status quo resets to the mean of the limit at the beginning and end
 of
 the interval.  (again, by year we really mean 52,560 blocks) The rolling
 median and periodic reset process ensures that the limit changes gradually
 and
 is not influenced by temporary events such as hacks to large exchanges or
 malicious wallet software.  The rolling median also ensures that for a
 miner
 the act of including a vote is never wasted due to the 

Re: [Bitcoin-development] Proposal: Vote on the blocksize limit with proof-of-stake voting

2013-06-10 Thread Pieter Wuille
On Mon, Jun 10, 2013 at 10:14 AM, Melvin Carvalho
melvincarva...@gmail.com wrote:
 However, Bitcoin's fundamental philosophy was one CPU one vote.

This is perhaps the largest misconception that keeps being repeated.
Bitcoin is not a democracy; it is a zero-trust system. The rules are
set in stone, and every full node verifies all rules and must
independently come to the same result as everyone else. Obviously, if
everyone changes their software, anything can change, but from within
the system there is no way to change which blocks are considered
valid, and there is certainly no voting mechanism about that.

What is voted about, is the one single thing that cannot be decided by
each node individually: namely the order of otherwise valid and
non-conflicting transactions, and that's just because it's a
necessity. Because deciding the order includes delaying transaction
potentially indefinitely, a majority of miners can indeed choose the
enforce an additional rule about which transactions are considered
valid, but the rules implemented in full nodes do not change without
changing the software. For example, miners cannot decide to raise the
block subsidy, even if every single miner out there would want that.
They'd just end up being ignored by everyone else.

 Voting is easily gamed.  While this may work in one particular case, it is
 perhaps a bad precedent to set.  Establishing methods of voting can lead to
 single points of failure.

The problem is that at some point, you have to look at the system from
a higher level than just the technical part. And because ultimately
the possibility exists where everyone changes their software, and
there is an exceedingly high incentive for consensus (a deliberate
hard-fork where two groups of users decide to use different and
incompatible rules, aware of eachother, is suicide for the system, in
my opinion). This results in the fact that proposed changes can indeed
become new adopted hard rules in the system, and I don't think there's
anything that can be done about it. Bitcoin is a consensus system - at
the technical level - but also a consensus of the people using it, and
ultimately they decide the rules.

 Unless there's a very good reason not to, e.g. miners are clearly abusing
 the system, we should stick with 1 CPU one vote.

So you're saying that instead of a zero-trust system, we should move
to a system where miners can decide _everything_ - as opposed to just
being in charge of ordering transactions? I don't think you understand
the system at all, if that is what you're proposing.

-- 
Pieter

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Re: [Bitcoin-development] Proposal: Vote on the blocksize limit with proof-of-stake voting

2013-06-10 Thread Mark Friedenbach

-BEGIN PGP SIGNED MESSAGE-
Hash: SHA1

John,

What you are recommending is a drastic change that the conservative
bitcoin developers probably wouldn't get behind (but let's see). However
proof-of-stake voting on protocol soft-forks has vast implications even
beyond the block size limit. Within Freicoin, we have looked at is as a
possibility for determining how to distribute the demurrage, a proposal
we are calling 'Republicoin' due to the fact that with proxy voting we
expect a system to emerge similar to the government budgeting in
parliamentary republics. Distributed, non-coersive government by
protocol, if you will.

So anyway, even if you get shot down, please continue to pursue this
proposal. It very likely has uses that you haven't thought of yet.

Cheers,
Mark

On 6/9/13 9:09 PM, John Dillon wrote:
 It has been suggested that we leave the decision of what the blocksize to be
 entirely up to miners. However this leaves a parameter that affects every
 Bitcoin participant in the control of a small minority. Of course we
can not
 force miners to increase the blocksize if they choose to decrease it,
because
 the contents of the blocks they make are their decision and their decision
 only. However proposals to leave the maximum size unlimited to allow
miners to
 force us to accept arbitrarily large blocks even if the will of the
majority of
 Bitcoin participants is that they wish to remain able to validate the
 blockchain.

 What we need is a way to balance this asymetrical power relationship.

 Proof-of-stake voting gives us a way of achieving that balance.
Essentially for
 a miner to prove that the majority will of the poeple is to accept a
larger
 blocksize they must prove that the majority has in fact voted for that
 increase. The upper limit on the blocksize is then determined by the
median of
 all votes, where each txout in the UTXO set is one vote, weighted by txout
 value. A txout without a corresponding vote is considered to be a vote
for the
 status quo. To allow the voting process to continue even if coins are
lost
 votes, including default votes, are weighted inversely according to
their age
 in years after 1 year. IE a vote with weight 1BTC that is 1.5 years
old will be
 recorded the same as a 1 year old vote weighted as 0.67BTC, and a 1
day old
 and 6 months old UTXO are treated equivalently. The 1 year minimum is
simply to
 make voting required no more than once per year. (of course, a real
 implementation should do all of these figures by block height, IE
after 52,560
 blocks instead of after 1 year)

 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

 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. The vote must
compute
 the median, rather than the mean, so as to not allow someone to skew
the vote
 by simply setting their value extremely high. Someone who still
remembers their
 statistics classes should chime in on the right way to compute a
median in a
 merkle-sum-tree.

 The slightly unusual construction of votes makes implementation by wallet
 software as simple as possible within existing code-paths. Votes could
still be
 constructed even in wallets lacking specific voting capability
provided the
 wallet software does have the ability to set nLockTime.

 Of course in the future the voting mechanism can be used for
additional votes
 with an additional vote_id. For instance the Bitcoin community could
vote to
 increase the inflation subsidy, another example of a situation where
the wishes
 of miners may conflict with the wishes of the broader community.

 Users may of course actually create these specially encoded txouts
themselves
 and get them into the blockchain.  However doing so is not needed as a
given
 vote is only required to actually be in the chain by a miner wishing to
 increase the blocksize. Thus we should extend the P2P protocol with a
mechanism
 by which votes can be broadcast independently of transactions. To
prevent DoS
 attacks only votes with known vote_id's will be accepted, and only for
 txid:vout's already in the blockchain, and a record of txouts for whom
votes
 have already broadcast will be kept. (this record need not be
authoritative as
 its purpose is only to prevent DoS attacks) Miners wishing to increase the
 blocksize can record these votes and include them in the blocks they
mine as
 required. To reduce the cost of including votes in blocks 5% of every
block
 should be 

Re: [Bitcoin-development] Proposal: Vote on the blocksize limit with proof-of-stake voting

2013-06-10 Thread Alan Reiner
One major problem I see with this, no matter how well-thought-out it is,
it's unlikely that those with money will participate.  Those with the
most stake, likely have their private keys behind super-secure
accessibility barriers, and are not likely to go through the effort just
to sign votes.  Not only that, but it would require them to reveal their
public key, which while isn't technically so terrible, large amounts of
money intended to be kept in storage for 10+ years will prefer to avoid
any exposure at all, in the oft-chance that QCs come around a lot
earlier than we expected.  Sure, the actual risk should be pretty much
non-existent, but some of the most paranoid folks are probably the same
ones who have a lot of funds and want 100.00% of the security that is
possible.   They will see this as wildly inconvenient.

I think this a great thought experiment, and I'd like to see where this
idea goes, in terms of designing ways for a decentralized community to
find consensus for important decisions, but I don't think that any idea
that requires users to dig up their private keys is going to be feasible
(or possibly reconstruct them from pieces and/or get multiple
signatures).  Especially if the system requires some kind of persistent
voting.

-Alan


On 06/10/2013 12:46 PM, Mark Friedenbach wrote:

 John,

 What you are recommending is a drastic change that the conservative
 bitcoin developers probably wouldn't get behind (but let's see).
 However proof-of-stake voting on protocol soft-forks has vast
 implications even beyond the block size limit. Within Freicoin, we
 have looked at is as a possibility for determining how to distribute
 the demurrage, a proposal we are calling 'Republicoin' due to the fact
 that with proxy voting we expect a system to emerge similar to the
 government budgeting in parliamentary republics. Distributed,
 non-coersive government by protocol, if you will.

 So anyway, even if you get shot down, please continue to pursue this
 proposal. It very likely has uses that you haven't thought of yet.

 Cheers,
 Mark

 On 6/9/13 9:09 PM, John Dillon wrote:
  It has been suggested that we leave the decision of what the
 blocksize to be
  entirely up to miners. However this leaves a parameter that affects
 every
  Bitcoin participant in the control of a small minority. Of course we
 can not
  force miners to increase the blocksize if they choose to decrease
 it, because
  the contents of the blocks they make are their decision and their
 decision
  only. However proposals to leave the maximum size unlimited to allow
 miners to
  force us to accept arbitrarily large blocks even if the will of the
 majority of
  Bitcoin participants is that they wish to remain able to validate the
  blockchain.

  What we need is a way to balance this asymetrical power relationship.

  Proof-of-stake voting gives us a way of achieving that balance.
 Essentially for
  a miner to prove that the majority will of the poeple is to accept a
 larger
  blocksize they must prove that the majority has in fact voted for that
  increase. The upper limit on the blocksize is then determined by the
 median of
  all votes, where each txout in the UTXO set is one vote, weighted by
 txout
  value. A txout without a corresponding vote is considered to be a
 vote for the
  status quo. To allow the voting process to continue even if coins
 are lost
  votes, including default votes, are weighted inversely according to
 their age
  in years after 1 year. IE a vote with weight 1BTC that is 1.5 years
 old will be
  recorded the same as a 1 year old vote weighted as 0.67BTC, and a 1
 day old
  and 6 months old UTXO are treated equivalently. The 1 year minimum
 is simply to
  make voting required no more than once per year. (of course, a real
  implementation should do all of these figures by block height, IE
 after 52,560
  blocks instead of after 1 year)

  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

  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. The vote must
 compute
  the median, rather than the mean, so as to not allow someone to skew
 the vote
  by simply setting their value extremely high. Someone who still
 remembers their
  statistics classes should chime in on the right way to compute a
 median in a
  merkle-sum-tree.

  The slightly unusual construction of votes makes implementation by
 wallet
  software as simple as 

Re: [Bitcoin-development] Proposal: Vote on the blocksize limit with proof-of-stake voting

2013-06-09 Thread John Dillon
-BEGIN PGP SIGNED MESSAGE-
Hash: SHA256

On Mon, Jun 10, 2013 at 4:44 AM, Edmund Broadley rebr...@gmail.com wrote:
 I really like this idea. I also like that users with no clue will leave
 their vote to the default chosen by the software developers, which hopefully
 will be 1MB. I like how coin age is factored in do votes are hopefully
 proportional to bitcoin assert ownership.

The default should *not* be set by wallets at all in fact. The default is that
by not voting, you accept the status quo, which is defined as the mean of the
old and new limits in the past year.

So lets say the limit is 1MB, and through voting it ends up at 2MB in one year.
Until that time by not voting you are in effect voting for the limit to be 1MB,
but after the next interval you not voting is equivalent to voting for a 1.5MB
limit. A subtle issue is then txout age, and at that point a 1.5 year old txout
should be like voting for the 1MB limit still, albeit weighted less. What you
don't want is your lack of vote to suddenly turn into a 1.5MB vote. This makes
sure that at all levels the increases are gradual rather than abrupt, although
the rate of increase may still be quite fast if the community votes that way.
(first derivative of the limit is a close approximation to a continuous
function)
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Re: [Bitcoin-development] Proposal: Vote on the blocksize limit with proof-of-stake voting

2013-06-09 Thread Peter Todd
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 setting their value extremely high. Someone who still remembers 
 their
 statistics classes should chime in on the right way to compute a median in a
 merkle-sum-tree.

I think the definition of the median requires knowledge of all the points so
it'll have to be a separate sorted tree - kinda complex unfortunately if
you really do want to be able to do full proof to SPV clients. Maybe
just putting the hash of the overall results in the coinbase is enough
for now.

The term to google is moving median - looks complex.

 Of course in the future the voting mechanism can be used for additional votes
 with an additional vote_id. For instance the Bitcoin community could vote to
 increase the inflation subsidy, another example of a situation where the 
 wishes
 of miners may conflict with the wishes of the broader community.

Good idea on keeping the code general.

 For any given block actual limit in effect is then the rolling median of the
 blocks in the last year. At the beginning of every year the value considered 
 to
 be the status quo resets to the mean of the limit at the beginning and end of
 the interval.  (again, by year we really mean 52,560 blocks) The rolling
 median and periodic reset