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Question: Bitcoin fork proposal by respected Bitcoin lead dev Gavin Andresen, to increase the block size from 1MB to 20MB.
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Author Topic: Bitcoin 20MB Fork  (Read 154258 times)
davout
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February 16, 2015, 05:52:51 PM
 #1541

There is no reduction in security.

It becomes much easier to pretend some blocks don't exist to selected targets, and get them to accept selectively rewritten history for just long enough to rip them off.

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NewLiberty
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February 16, 2015, 05:56:17 PM
 #1542

There is no reduction in security.

It becomes much easier to pretend some blocks don't exist to selected targets, and get them to accept selectively rewritten history for just long enough to rip them off.

This security risk is balanced by the correspondingly increased number of nodes, given an equivolent Bitcoin Network Cost, where:
Bitcoin Network Cost = Data Size * Decentralization.

So the net result is no decrease in security.

We can expect a marginal increase in security as the node maintenance cost becomes less 'chunky'.

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DeathAndTaxes
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February 16, 2015, 06:00:39 PM
Last edit: February 16, 2015, 06:34:53 PM by DeathAndTaxes
 #1543

There is no reduction in security.

It becomes much easier to pretend some blocks don't exist to selected targets, and get them to accept selectively rewritten history for just long enough to rip them off.

All nodes maintain a full copy of the blockheaders.   If you can prevent a node from obtaining a block then you can denial of service the validation of the chain but you can't trick a node into thinking a block doesn't exist.  An attacker can't fake the content because that would require a preimage of the blockhash.  If one peer refuses to provide a block, you can ask another peer.  If all of them also refuse you can connect to new peers.  If you are unable to find a single peer to provide the requested block then you can't validate the chain but the attack is limited to a denial of service.  If a full node hasn't received all the blocks then it hasn't synced and it can't validate transactions.  It should not provide unvalidated information to the user.

With the blockheaders of the longest chain a node knows the full set of blocks that exist.  It may not know the contents yet but it already knows they exist.
davout
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February 16, 2015, 06:10:01 PM
 #1544

This security risk is balanced by the correspondingly increased number of nodes, given an equivolent Bitcoin Network Cost, where:
Bitcoin Network Cost = Data Size * Decentralization.

You can't arrive to meaningful conclusions if you base your reasoning on undemonstrated equalities.


All nodes maintain a full copy of the blockheaders.   If you can prevent a node from obtaining a block then you can denial of service the validation of the chain but you can't trick a node into thinking a block doesn't exist.  An attacker can't fake the content because that would require a preimage of the blockhash.  If an attacker has the valid block his only option is to not provide that block but that exists today with full nodes.  If all your peers refuse to provide you a requested block you can't validate the chain.  This however is limited to a denial of service.   If a full node hasn't received all the blocks then it hasn't synced and it can't validate transactions anyways.  If it is then the node is flawed and insecure.   

With the blockheaders of the longest chain a node knows the full set of blocks that exist.  It may not know the contents yet but it already knows they exist.

Yes, I was reasoning in the context of a "hey, i'm getting back online, what's the network been up to?" scenario.

traincarswreck
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February 16, 2015, 06:21:02 PM
Last edit: February 16, 2015, 06:42:18 PM by traincarswreck
 #1545

So...

Have we reached our consensus yet?

And do we know yet what is "Ideal Money"?

(euro/greek talk http://ec.europa.eu/avservices/ebs/live.cfm?page=2)

Quote from: Ideal Money
But if, for example, all of the countries of the world would base the value for their national currencies on the value of the british currency then this situation would appear singular and unstable, while it was not so singular for a lot of countries to base their currency value on gold.
DeathAndTaxes
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February 16, 2015, 06:28:43 PM
 #1546

Yes, I was reasoning in the context of a "hey, i'm getting back online, what's the network been up to?" scenario.

It is true that if you do not know the longest chain then you have no security.  That is the foundation on which all other layers of security depend.  Running a full node will not make you any more secure if you can not connect to at least one honest node.  All nodes (including full nodes) must know the chaintip of the longest chain in order to sync in a trustless manner.
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February 16, 2015, 06:36:18 PM
Last edit: February 16, 2015, 06:58:06 PM by Cryddit
 #1547

Quote

No. He is talking about the 970-980 kB blocks which not rare these days. While the average is around 300kB, that means we are at 1/3 capacity. And I personally think 1/3 is where we should seriously consider our options for scalability. The way people are split on the subject right now it is even more urgent to start getting a consensus.

But on the other hand there is no hurry and no crisis. The extra transactions can just go through altcoins if Bitcoin chooses the 1MB block + higher fees 'solution'. Wink

They aren't rare, but they are not the norm.  Most aren't near full.
F2Pool solved a few that were close recently, above 900K.  With a good number of freebies.

https://blockchain.info/block/0000000000000000175b44859017a5148c48ecba7a67f14012232e9bb6b47a73

https://blockchain.info/block/00000000000000000f9597aed448ce8429c550a65f896b66760381d0c364901e

and then there is this 7K block in between
https://blockchain.info/block/000000000000000014efb22561313ebe3c27780808b5d8939ebc1a850badf9da

There are a lot of blocks with <200K, so we'd get some scalability of more Tx/s with a minimum block size too, but that would not be a good thing to do.

The more merchant involvement there is, the more we need to be thinking about the spikes associated with merchant business.   We need to think about what happens at 8 AM Pacific Time on Black Friday - when the local credit card network in the places where I shopped couldn't handle the traffic and were knocked offline for an hour and then backlogged for the next six.

The more trader business there is, the more we need to be thinking about the spikes associated with exchange businesses.  We need to think about what happened in the markets the next day after Jim Leeson took down Barents, when the mortgage meltdown chain reaction set in after Lehman Bros. defaulted and made $trillions evaporate overnight, when Madoff announced that his $billions were all part of a Ponzi scheme, and when Cyprus announced its plan to just TAKE whatever money people happened to have trusted banks with.  When people finally take that 'Beware False Profits' message to heart, odds are they'll want to trade into Bitcoin.  It'd be a real shame if they can't.

And we also need to consider the enormous follow-on effects of government decisions that change the rules more broadly.  We need to think about what happens at 8 AM GMT on the International Currency Exchange the day after Brussels announces that Europe will either form a fiscal union (ie, have a uniform tax law and a uniform policy for allocation of the funds so collected) or end its attempt to have a common Euro fiat currency without one.  'Cause that's going to happen - what they've got now isn't a stable configuration in the long term.

I think there's all kinds of reasons why, when we need bigger volume, we're going to need enormous amounts of it very suddenly.  The call for bigger volume is sometimes a result of predictable but large events, and sometimes a response to statistical 'Black Swan' events that result in a scramble to reach a new balancing point far from the old one.

We're seeing spikes to 1MB now, even without driving events we can point at. So, at the moment when 1MB definitively isn't enough, I fear that 5MB won't be enough either.  Transaction volume in the real world is incredibly spiky in response to such events, and Bitcoin is starting to have closer and closer interactions with the 'real world.'

Cryddit
davout
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February 16, 2015, 06:40:06 PM
 #1548

All nodes (including full nodes) must know the chaintip of the longest chain in order to sync in a trustless manner.

That's backwards.

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February 16, 2015, 06:56:09 PM
Last edit: February 16, 2015, 07:24:33 PM by DeathAndTaxes
 #1549

All nodes (including full nodes) must know the chaintip of the longest chain in order to sync in a trustless manner.

That's backwards.

No it isn't.
NewLiberty
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February 16, 2015, 06:59:34 PM
 #1550

This security risk is balanced by the correspondingly increased number of nodes, given an equivolent Bitcoin Network Cost, where:
Bitcoin Network Cost = Data Size * Decentralization.

You can't arrive to meaningful conclusions if you base your reasoning on undemonstrated equalities.

gmaxwell put out a recent and good discussion on this, in regards to this topic here:
https://bitcointalk.org/index.php?topic=946236.msg10369307#msg10369307

Though he calls it the "inherent cost of transactions", this is the bitcoin network's fundamental cost and value added for if there are no transactions ever again, there is not any more meaning to Bitcoin.

What sort of demonstration are you seeking?  Why is this in doubt?

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NewLiberty
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February 16, 2015, 07:02:22 PM
 #1551

We're seeing spikes to 1MB now, even without driving events we can point at. So, at the moment when 1MB definitively isn't enough, I fear that 5MB won't be enough either.  Transaction volume in the real world is incredibly spiky in response to such events, and Bitcoin is starting to have closer and closer interactions with the 'real world.'

So in your formulation, a single block is a meaningful spike?

If so, there isn't a max block size that can accommodate.

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davout
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February 16, 2015, 07:21:09 PM
 #1552

All nodes (including full nodes) must know the chaintip of the longest chain in order to sync in a trustless manner.

That's backwards.

No it isn't.

It's backwards in the sense that nodes sync in a trustless manner to gain knowledge of the tip, not the other way around.
I wasn't following up on the pruning discussion.

davout
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February 16, 2015, 07:24:51 PM
 #1553

gmaxwell put out a recent and good discussion on this, in regards to this topic here:
https://bitcointalk.org/index.php?topic=946236.msg10369307#msg10369307

Though he calls it the "inherent cost of transactions", this is the bitcoin network's fundamental cost and value added for if there are no transactions ever again, there is not any more meaning to Bitcoin.

What sort of demonstration are you seeking?  Why is this in doubt?

He seems to simply be asserting it without actually backing it in any way.
If taken for granted it actually weakens the hardforkers' position.

Cryddit
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February 16, 2015, 07:29:30 PM
 #1554

Quoting myself from another thread....  given a bit of data, I think 12x average utilization is probably a very good target for a maximum utilization.  It seems to work for VISA (most of the time, at any rate).  That would put us at 3600KB blocks for now, and if there's a "phase shift" where utilization suddenly goes up by a factor of 100, we'd be able to adapt within a couple of weeks, meaning before the opportunity is completely gone.

Really, what I'm worried about is the 'phase shift' scenario.  I've worked at a bunch of startups, and when a new thing hits, it tends to hit suddenly and hard.  At a completely unpredictable time, after/during years of hard work during which you don't know whether it's going to happen let alone when.  

If Bitcoin goes mainstream, it will not do so gradually; it will be a phase shift where, a few months after 'a few' people are using it here and there, 'everybody' is using it all the time.  

I think we need an adaptive limit because the exponential growth outlined by Gavin is too slow to handle that kind of rapid  phase shift.  It's the right shape for the curve, but the curve happens over a period of twenty weeks, not over a period of twenty years.  And you never know when the curve you need to respond to is ready to begin.   Not being ready to roll out and scale, QUICKLY, could result in missing it when the opportunity does happen.  Scaling in advance of need, on the other hand, simply invites the waste of resources.

All that said, yes, I am STILL in favor of raising the block size limit, whether it is done the way I'd prefer it, or not.  As far as I'm concerned, this proposal is still "HELL YES" even though I think I might know a better way to do it, because not doing either thing would make failure certain.

VISA only has an average txn capacity of 2,000 tps but their network can handle a peak traffic of 24,000 tps.  Nobody designs a system with a specific limit and then assumes throughput will be equal to that upper limit.

That is a very valuable observation.  An 'adaptive' block size limit would set a limit of some multiple of the observed transaction rate, but most of its advocates (including me) haven't bothered to look up what the factor ought to be. what you looked up above presents real live information from a functioning payment system.  

The lesson being that an acceptable peak txn rate for a working payment network is about 12x its average txn rate.  

Which, in our case with average blocks being around 300 KB, means we ought to have maximum block sizes in the 3600KB range.  

And that those of us advocating a self-adjusting block size limit ought to be thinking in terms of 12x the observed utilization, not 3x the observed utilization.


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February 16, 2015, 07:31:01 PM
 #1555

Quoting myself from another thread....  given a bit of data, I think 12x average utilization is probably a very good target for a maximum utilization.  It seems to work for VISA (most of the time, at any rate).  That would put us at 3600KB blocks for now, and if there's a "phase shift" where utilization suddenly goes up by a factor of 100, we'd be able to adapt within a couple of weeks, meaning before the opportunity is completely gone.

But then we won't have "ideal money"...

Quote from: Ideal Money
The actors on the stage of the drama formed by the actions that determine the trends in the value of a national currency are themselves players in a game and they can be rationally viewed as such. The theme of "rational expectations" naturally enters. Those who ARE NOT in control but who ARE naturally concerned with the expectations for the value trend of a national currency cannot be wisely assumed to be entirely naive and unable to form "rational expectations" regarding the currency. So the (possibly) "Keynesian" players in this game have natural opponents (or co-players, beyond zero-sum perspectives) who are interested in not being themselves "outsmarted" by those who control the options that determine, say, the quantity supplied of the national currency.
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February 16, 2015, 07:31:55 PM
Last edit: February 16, 2015, 07:49:07 PM by DeathAndTaxes
 #1556

All nodes (including full nodes) must know the chaintip of the longest chain in order to sync in a trustless manner.

That's backwards.

No it isn't.

It's backwards in the sense that nodes sync in a trustless manner to gain knowledge of the tip, not the other way around.
I wasn't following up on the pruning discussion.

Which is dependent to access to at least one honest peer.  You can't fully sync if you don't have access to at least one peer that can provide you blockheaders up to the chaintip of the best chain.  Maybe I worded it poorly but it was in response to this false claim.

Quote
It becomes much easier to pretend some blocks don't exist to selected targets, and get them to accept selectively rewritten history for just long enough to rip them off.

If a node has the full set of headers then it can't be tricked into thinking a block on the longest chain doesn't exist.  In order for a node to obtain the full set of headers it must have at least one honest peer which also has a copy of that full set of headers.  This is independent of the number of peers have a particular block of the blockchain.  Pruned nodes or a DHT node do not reduce the number of copies of the blockheaders, they reduce the number of copies of blocks.  Full blocks are not needed to determine the longest chain in a trustless manner.  If it was than SPV clients would be impossible as well.  To trick a node into thinking a 'block doesn't exist' requires an attacker keep that node from learning of one or more blockheaders.  If the node has the blockheader for most recent block it know the block exists.  It may not (yet) know the contents but it certainly knows it is exists.  A node which knows a block exists but doesn't know the contents of that block is not yet done syncing.
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February 16, 2015, 07:36:24 PM
 #1557


Even if the miners were dumb enough to broadcast the new version and triggered the fork, that doesn't mean they will stay on the fork. They will soon find that it is not possible to sell their USGavincoins for the price they were expecting. And seeing as how mining is a barely profitable venture (due to adjusting difficulty), they will be forced to switch to the original chain or shut down entirely.

This makes so much nonsense it's breathtaking.  It is a single, perfect, priceless jewel that deserves to be preserved for all time.  I was unaware that such pure examples of nonsense existed in the modern world.  I am humbled before a true master.
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February 16, 2015, 07:54:45 PM
 #1558


This makes so much nonsense it's breathtaking.  It is a single, perfect, priceless jewel that deserves to be preserved for all time.  I was unaware that such pure examples of nonsense existed in the modern world.  I am humbled before a true master.
It is helpful, in dialogue, to stay "mature".  And also to have read the relevant materials.

On the one hand, I am of the impression the best decision would be make a decision that supports the creation of "Ideal Money".

Yet on the other hand, it seems we do need some form of (general) consensus which could even involve compromise in that regard.

And then further to another hand the "idealness" of a currency seems to be related somehow to the psychological and especially in regards to the future stability of it:
Quote from: Ideal Money
   From the viewpoint of parties domiciled outside of the territory of where a specific currency (such as, e.g. the currency of Brazil) is established the "quality" of that currency is evaluated according to the reasonable appraisals of the probabilities of loss in value of the unit of that currency, particularly in comparison with other currencies and also in comparison with alternatives available for  use for "storage of value", like gold or commodities in general.
    The more that the probabilities of loss seem to be large the more that currency will be evaluated as of "low quality".
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February 16, 2015, 07:55:58 PM
 #1559

It doesn't matter what miners want. If you had truly been reading the logs, you would have known that.

Yes it matters what miners want.

I guess you don't follow hyperlinks, or know how to use them for that matter. Moving on...

I think I have read most of what has been written on the subject, including the 2 last years of trilema (and some older articles) + months of logs of b-a.

I have not seen where or how the old bitcoin would survive :
- under a difficulty that matches a target for which it has 5% of the required hashrate
- under the risk of an attacker committed to write empty blocks on the chain as long as it is possible

I do not say :
- that the gigablockchain is a good idea,
- or that a majority of miners will switch to it.

What I say is that IF miners switch, with 95% of the hashrate or more, THEN the old chain is dead. And I don't see any arguments that could explain how it could be any different from what MP himself wrote here.

If you've read so much of the log and trilema then why aren't you in the WoT? Get on that.

Even if the miners were dumb enough to broadcast the new version and triggered the fork, that doesn't mean they will stay on the fork. They will soon find that it is not possible to sell their USGavincoins for the price they were expecting. And seeing as how mining is a barely profitable venture (due to adjusting difficulty), they will be forced to switch to the original chain or shut down entirely.

You are assuming that some miners will make the voluntary choice to switch to gavincoin, then wait for at least 95% of other miners to do the same, then do the hard fork, then see that the legacy-bitcoin is stalled at 0 tps, which will mean that, contrarily to my original belief, there will be no market for mpcoin, and then switch back to mpcoin ?

I am sorry but I don't understand how your brain allows you to believe that.

No. You are assuming that there will be a market for USGavincoins. Who is supposed to buy these things? MPEx won't accept them. Maybe you don't think that means much, but that's 31 thousand bitcoin monthly volume that won't take place on the new chain. If #bitcoin-assets users aren't going to buy Gavin's altcoin, who is? Seriously where is the support going to come from? At least some of the miners will necessarily have to remain on the old chain to meet the demand of MPEx users. The real question is, how many miners will stick with the new chain? I guess there will be a little bit of demand for it to support some change tipping, but it's nowhere near 31 thousand bitcoin a month worth.

How does my brain believe this? I'm actually using it. Try it some time.

Marriage is a permanent bond (or should be) between a man and a woman. Scripture reveals a man has the freedom to have this marriage bond with more than one woman, if he so desires. But, anything beyond this is a perversion. -- Darwin Fish
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February 16, 2015, 08:17:49 PM
 #1560


Even if the miners were dumb enough to broadcast the new version and triggered the fork, that doesn't mean they will stay on the fork. They will soon find that it is not possible to sell their USGavincoins for the price they were expecting. And seeing as how mining is a barely profitable venture (due to adjusting difficulty), they will be forced to switch to the original chain or shut down entirely.

This makes so much nonsense it's breathtaking.  It is a single, perfect, priceless jewel that deserves to be preserved for all time.  I was unaware that such pure examples of nonsense existed in the modern world.  I am humbled before a true master.

To expand on my previous post, there is also the matter of the sell pressure that will come from us "anti-forkers." So not only will Gavin's spambots need to support the usual 36 hundred bitcoin mined per day, but they will have to take on thousands if not millions of double-spent coins that were purchased before the fork. It's really comical that you guys think you have even the slightest sliver of a chance to win this thing. But by all means, quote me and laugh; I'll have the last one.

Marriage is a permanent bond (or should be) between a man and a woman. Scripture reveals a man has the freedom to have this marriage bond with more than one woman, if he so desires. But, anything beyond this is a perversion. -- Darwin Fish
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