Quote from: jbreher on February 17, 2016, 05:18:04 AM

Quote from: madjules007 on February 17, 2016, 12:18:50 AM

So, centralization endangers security and fungibility, but "the network would operate just fine" if validators were centralized into smaller and smaller groups that omitted the vast majority of the userbase? At what point does it become "too centralized?"

Move goalposts much? As long as there is the _ability_ for anyone to run a node (i.e. no regulatory or exclusionary barrier), I am unconcerned about any amount of node centralization. After all, independent nodes add zero value. They can always be routed around by any other network entities. They are essentially non-entities as far as the network is concerned.

How have I moved the goalposts? The whole point is that as block size has increased, the ability for anyone to run a node, on average, has decreased. We have reason to believe this will continue until bandwidth bottlenecks are mitigated.

You keep saying "independent nodes add zero value" but you've done nothing to prove it. How exactly can nodes simple be "routed" around? How does one discriminate among nodes that are enforcing the same consensus rules? When your node connects with other nodes, you can't control which nodes they connect to. Unless a single entity controls a majority of nodes in the network, independent nodes absolutely cannot be "routed around."

Again:

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If miners could trivially bypass any nodes, that would suggest that a Sybil attack would be trivial to mount, correct?--as they could simply bypass all honest nodes. Miners have carried out attacks in the past, so why not Sybil attacks? If it's so easy to bypass the entire decentralized node system, why aren't miners attacking the userbase for profit on that basis? If miners can trivially control most nodes, they can censor and double-spend all day until the cows come home. Yet.... this doesn't happen. Why?

Quote from: jbreher on February 17, 2016, 05:18:04 AM

Perhaps you can explain to me -- in detailed fashion -- exactly what value you think it is that independent nodes provide? What task do they perform that cannot be countered? How exactly does their presence prevent nefarious action?

Here is a summary:

Quote from: madjules007 on February 14, 2016, 09:29:43 AM

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Every node must receive and process every transaction in every block. That distributes blockchain data to all nodes who enforce the rules, rather than a system where nodes trust a central source. [i.e. decentralization as a solution for the security faults of trust]

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The more nodes that exist that are enforcing the same rules, the more likely the longest valid blockchain data that you receive from them is accurate.

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If there are only mining nodes, the userbase, by definition, trusts miners. Hence why the existence of non-mining nodes secures bitcoin: by decentralizing hash power from validating nodes.

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One of the primary determining factors in whether a Sybil attack is possible is how cheaply identities (nodes) can be generated. The more nodes there are, and the more decentralized said nodes are, the bigger the cost of mounting a Sybil attack, since attackers must set up more nodes in more distinct locations.

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There have been past double-spend attacks by miners, so we know that rational miners will attack nodes if it is profitable to do so. That they have not used Sybil attacks specifically does not prove that it is not (and was not historically) possible to do so, but it certainly does not help your claim that non-mining nodes do nothing to secure the system. If they did nothing -- like padlocks on the lawn -- wouldn't that suggest it was cheap enough to attack them with Sybils?

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Non-mining nodes obviously aren't impotent because we are talking about theoretical Sybil attacks, not historical ones.

In summation: Nodes enable a decentralized, trustless system to exist in the first place (securing users' funds from centralization failure). They are the system's defense against Sybil attacks (preventing double-spending and censorship attacks) from miners or other attackers. Further, nodes, by self-validating, also decrease the number and scope of attacks on users of the system by eliminating trust-based protocols.

Quote from: jbreher on February 17, 2016, 05:18:04 AM

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Hash power is already highly centralized among a handful of pools; merchants almost entirely transact through two central processors (Bitpay and Coinbase); there are a handful of prominent exchanges and a couple handfuls more of dodgy, scammy ones. The network would run just fine if the entire userbase trusted these few entities to uphold the integrity of all transactions?

It doesn't matter whether or not we trust this small set. Any other nodes can be routed around.

Firstly, no, they can't be. Not unless an attacker can control who the network connects to (i.e. a Sybil attack). Secondly, this unfounded idea that all honest nodes can be trivially bypassed has nothing to do with the point I alluded to -- that node centralization introduces trust to the network by reducing redundancy and increasing reliance on a smaller group of validators.

Quote from: jbreher on February 17, 2016, 05:18:04 AM

But to answer your implied question, as long as transaction originators (i.e. exchanges, merchants, and wallets) are necessary nodes on the network, I expect their users will keep them honest. This does not omit the majority of the userbase, these entities are representative of the userbase.

Why should we trust that a business' customers will keep them honest? The whole point of having a network of peers propagating redundant information is that we don't need to place trust in Coinbase to be honest.

Bitcoin is P2P. We have no need for entities to "represent" us. The protocol does that for us. All we need to do is run nodes.

That's right. Bitcoin was conceived of as a trustless, P2P protocol. I'm beginning to wonder what coin you're talking about.

Quote from: jbreher on February 17, 2016, 05:18:04 AM

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If the entire userbase stopped running nodes (save for this few dozen entities), are you suggesting that it would not be easier for say, a miner or a government, to mount a Sybil attack on the network?

Why don't you first explain to me why you think independent nodes provide any sort of protection from Sybil attacks? Actually, first, why don't you describe to me exactly what form of Sybil attack you are concerned about here?

Regarding the first question, see the summary I quoted above. Regarding the second:

https://en.bitcoin.it/wiki/Weaknesses

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Sybil attack

An attacker can attempt to fill the network with clients controlled by him, you would then be very likely to connect only to attacker nodes. Although Bitcoin never uses a count of nodes for anything completely isolating a node from the honest network can be helpful in the execution of other attacks.

This state can be exploited in (at least) the following ways:
-The attacker can refuse to relay blocks and transactions from everyone, disconnecting you from the network.
-The attacker can relay only blocks that he creates, putting you on a separate network. You're then open to double-spending attacks.
-If you rely on transactions with 0 confirmations, the attacker can just filter out certain transactions to execute a double-spending attack.
-Low-latency encryption/anonymization of Bitcoin's transmissions (With Tor, JAP, etc.) can be defeated relatively easy with a timing attack if you're connected to several of the attacker's nodes and the attacker is watching your transmissions at your ISP.
-The attacker can see all of your transactions through the use of special programs.

Quote from: jbreher on February 17, 2016, 05:18:04 AM

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Honesty is not the issue here; network security is the issue.

Agreed. However, the Core SegWit Omnibus Changeset requires as much or more data transfer and storage by each fully validating node than does a simple 2MB bump. The necessary consequence of this is that using 'ZOMG centralization of the poor nodes' as a reason for Core SegWit Omnibus Changeset over simple 2MB is absolute twaddle.

How so? Operators that don't update their nodes out of bandwidth concerns aren't pressured to drop offline. Operators that update to Segwit see reduced fees by using less block space, and increased throughput by segregating signature data. That's the beauty of backwards compatibility and it's win-win for both capacity and decentralization.

Quote from: jbreher on February 17, 2016, 05:18:04 AM

Well, duh. We already have a solution for not-fully-validating wallets. Explain what you mean by 'externalizing the cost to all nodes' -- sounds an awful lot like 'trusting others to do the validation'. Care to explain how it differs?

If you're suggesting that SPV nodes are comparable to non-Segwit nodes, back up your claim. You keep suggesting that segregating signature data leads to trust issues. Signatures authorize TX outputs from the original owners. Notably, fully validating signature data means maintaining gigabytes of signatures that are buried under years of proof-of-work (Segwit also allows for pruning of this historical data). Signature data does not impact the TX ID; it has never been in the UTXO set; it's just a piece of data that is included with the TX hash. In other words, Segwit is optimizing transaction throughput by segregating the part of transactions that do not affect transaction validity (block validation will need to be addressed per the current architecture, though). And that's the case under the current rules. This aspect of Segwit is more akin to blockchain pruning than anything you're suggesting.

If you are suggesting a potential attack vector that exploits the segregation of signature data, please outline it. (crickets)

https://en.wikipedia.org/wiki/Cost_externalizing

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how a business maximizes its profits by off-loading indirect costs and forcing negative effects to a third party.

= distributing the cost of increased (unoptimized) throughput to nodes ... rather than optimizing throughput.

Quote from: jbreher on February 17, 2016, 05:18:04 AM

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Quote from: jbreher on February 15, 2016, 07:21:11 PM

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I don't think anyone here is really arguing about disk space. But could you provide some evidence that "an insignificant proportion of current nodes will stop node-ing" if block size doubles? No data I've seen appears to support that, but maybe you could provide some.

Merely a rationally reasoned conclusion. Can you support an assertion to the contrary?

So... you cite no evidence.

I see you cite no evidence as well.

I guess you missed the quote below, as you conveniently ignored it. Statistical, logical and anecdotal evidence. We cannot "prove" why operators have persistently chosen to shut down their nodes as block size has steadily increased. But the point here is not proof. The point is that logically, and based on infrastructural bandwidth limits, bandwidth bottlenecks are a plausible cause that fits the correlation. As such, we need to plan for it. Engineering, particularly when dealing with large scale systems, is about planning for worst case scenarios... not assuming that nothing can ever go wrong. Proof of worst case scenarios does not exist until they occur.

Anyway:

Quote from: madjules007 on February 17, 2016, 12:18:50 AM

For starters, there is a clear negative correlation between node health and block size. As average block size increases, average node count falls. This is a recurrent trend over past years.

Logically, since bandwidth is the only major infrastructural bottleneck for nodes, one could surmise that if bandwidth requirements were low enough, non-broadband -- mobile, dialup, ham radio, etc. -- users could operate a node, and further, that some would run nodes (after all, some users evidently still run nodes despite the availability of SPV). Conversely, as bandwidth requirements increase against a static bandwidth cap (as is commonly in place for cable customers), that decreases the bandwidth a user can allocate towards running a node or towards another bandwidth-heavy activity, increasing the likelihood that the node will simply be shut down for lack of resources. When only 25% in a highly industrialized country (the US) have fiber connections, it's prudent to assume that most people are limited to at best cable internet (frequently bandwidth-capped), and at worst non-broadband connections that prohibit users from running a node at all.

Given the persistent negative correlation between node health and growth in block size, and given that upload bandwidth is a measurable pressure on nodes who are known to have bandwidth limits (speed in the case of DSL and satellite, and total bandwidth consumed in the case of cable), we have good reason to believe that there is a causal relationship at work here between node health and growth in block size.

Anecdotally, many on this forum have echoed the sentiment -- as do I -- that bandwidth is the only pressure that has ever caused us to shut down our nodes. I was recently lucky enough to upgrade to a fiber connection, but as recently as a few months ago, I refused to run a node full-time due to being capped by Time Warner Cable. Further, the operation of VPS nodes (which we cannot realistically estimate the quantity of) is in theory problematic since these nodes are not physically controlled by the operator, causing us to question how much it really adds to decentralization in attack scenarios.

Quote from: jbreher on February 17, 2016, 05:18:04 AM

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Then you cite "rationality" as the basis for your claims, without explaining the rationale.

Waah. Where's your rationale?

That decentralization is paramount to any other concerns, and that increasing block size (under the current bandwidth requirements and limitations) will quite obviously increase node centralization -- the extent to which is unclear.

Quote from: jbreher on February 17, 2016, 05:18:04 AM

Whatevs. Anyone running a node today is quite evidently interested in bitcoin. After all, they've devoted more than three dollars worth of disk space to the activity. And enough bandwith to (almost) carry on a Skype conversation. I don't think such a person is going to be deterred from running a node just because the cost rises to six bux and change in disk, and a bit more bandwidth than a Skype conversation. That's my rationale.

Right, right. Nodes get chopped in half in a couple years and...no one could ever be deterred from running a node because...Skype.

Quote from: jbreher on February 17, 2016, 05:18:04 AM

But it really doesn't matter, as independent nodes add no value to the network (see above).

They do. (See above)

Quote from: jbreher on February 17, 2016, 05:18:04 AM

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For starters, there is a clear negative correlation between node health and block size. As average block size increases, average node count falls.

If there's a point there, you're not making it. Coincidence does not imply causality. And your correlation is poor. Need more rigor if you're trying to claim causality here.

That's just dishonest of you. I stated the correlation, then went on to write three paragraphs laying out the statistical, logical and anecdotal evidence to suggest that there may be a case for causality. You simply ignored it. I re-quoted it above for you.

Since I've made quite an effort to provide evidence for causality, perhaps you could explain the negative correlation between node health and block size. Can you not even entertain the possibility that increasing bandwidth requirements deters the operation of nodes? If not, then at least formulate some sort of argument.

Quote from: jbreher on February 17, 2016, 05:18:04 AM

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If miners could trivially bypass any nodes, that would suggest that a Sybil attack would be trivial to mount, correct?

Before I can either disagree or agree with your proposition, you are going to first have to define the characteristics of this Sybil attack of which you speak. Then you are going to have to explain to me why you think any independent node might prevent such an attack. Care to do so?

I've done so above. Rather, it's a robust network of nodes that defends against Sybils. The very basis of a Sybil attack is filling the network with nodes you control. The more honest nodes there are, the more difficult such an attack is to mount. This is very, very basic.

Quote from: jbreher on February 17, 2016, 05:18:04 AM

Or more germane, which part of my statement are you trying to refute, by ignoring it in favor of your own proposition? Do you disagree that any miner could implement their own forwarding node? Do you disagree that said miner could connect explicitly to specific nodes? Do you disagree that these other nodes might be owned by other miners? Do you disagree that these other miners might plausibly have the same game intent as others? Or that the cost of such node be essentially noise to an industrial mining operation? What else in my assertion could you possibly be disagreeing with?

I didn't ignore anything. I plainly laid out why your assertion that miners can simply "route around" any nodes they want and therefore attack the system as they please was ridiculous.

A miner can communicate with whoever they want. They can communicate with other miners, sure. Other miners may share the same intentions (though we could never assume that; they are competing entities). But past the first degree of contact -- said miners have zero control over whom the nodes they connect to, connect to. Unless an attacker physically controls a node, he cannot control who it connects to. The network effect among nodes prevents any such "bypassing" of nodes. They can't "route around" anything unless they control a majority of either hash power or nodes.

And the cost of running a node =/= the cost of mounting a Sybil attack.

Quote from: jbreher on February 17, 2016, 05:18:04 AM

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--as they could simply bypass all honest nodes. Miners have carried out attacks in the past, so why not Sybil attacks? If it's so easy to bypass the entire decentralized node system, why aren't miners attacking the userbase for profit on that basis? If miners can trivially control most nodes, they can censor and double-spend all day until the cows come home. Yet.... this doesn't happen. Why?

Bullshit. But I'll first answer your questions - because it is not in their rational self interest.

Miners have carried out attacks in the past. Double spend attacks, withholding attacks. "But..... I thought they would never do that because of rational self-interest!!!" No. If an attack is profitable, a miner will carry it out. That's what logic says, that's what history says. Miners are fairly anonymous too; there is really no rational reason not to attack nodes or other miners if it is profitable to do so. After the attack, they can simply point their hashpower elsewhere, pools can shut down and reopen under new names, etc.

You trust miners far too much.

Quote from: jbreher on February 17, 2016, 05:18:04 AM

What proportion of miners do you think it is that does not broadcast to other miners? Do you understand that every hop in the chain adds latency, and thereby increases the chance that their block will be orphaned? In the light of this, why on earth would they trust the broadcast to some ad-hoc association of fly-by-night independent nodes, when they can broadcast directly to other miners? Or to the (oddly centralized) relay network?

I'm unsure why you're so obsessed with this idea of miners communicating with miners. Miners are not the only actors; nodes determine blockchain validity, not hashpower. Miners still need to propagate to the network; their blocks are still subject to validation by the every node in the network. You can keep telling yourself that some cabal of miners is responsible for validating the blockchain... but they answer to a much larger network of nodes that tells miners what is the longest valid blockchain:

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Miners are at the whims of nodes. Running an ASIC farm doesn't give you any rights over what node software I run. And an army of nodes enforcing bitcoin's rules (including a 1MB block size limit) is here to tell you that they do not give a shit about the opinions of miners.

Quote from: jbreher on February 17, 2016, 05:18:04 AM

I never said miners could control most nodes, I said that independent nodes are of no value in keeping miners in check.

That's because you fundamentally misunderstand why the inability for miners to control most nodes, by definition, prevents them from being able to mount certain attacks on the userbase.

Quote from: jbreher on February 17, 2016, 05:18:04 AM

Any given miner cannot truly censor any given transaction, when the next miner to solve a block might include the 'censored' transaction. No value in trying. And independent nodes would have no power to stop this anyhow. Each miner is the sole determinant of what transactions to include in any given block. What power does any node have to 'anti-censor'?

We're not only talking about miners. Governments, for instance, may have reason to launch censorship attacks. In a successful Sybil attack, it doesn't matter if another miner tries to include the censored transaction. If the attacker controls most nodes, he determines what transactions and blocks are valid or invalid to the rest of the network; he can simply render those blocks invalid.

Quote from: jbreher on February 17, 2016, 05:18:04 AM

Any given miner attempting to double-spend will find his double-spent transactions (thereby blocks) ignored by the rest of the mining network. Thereby losing his entire block reward. And independent nodes would have no power to stop this anyhow. Explain why you think otherwise?

Not if he has enough hashing power.

I'm not sure what kind of attack you're referring to. But as I've made the case for several times, the existence of nodes is the only defense against particular frauds based on a Sybil attack. If nodes were sufficiently centralized that an attacking miner could control the majority of nodes, the rest of the mining network is irrelevant. Again, hashpower is irrelevant to blockchain validity. The attacker can double spend all he wants, since he controls what the networks agrees is valid.

Quote from: jbreher on February 17, 2016, 05:18:04 AM

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That miner you mention is also competing against all other miners to have his blocks ~~validated by most nodes~~ accepted by the next miner to mine a block, so the presence of honest ~~nodes~~ miners disincentivizes him from attempting any attack on that basis ... "Bypassing any set of independent nodes" is meaningless if most ~~nodes~~ miners on the network are still enforcing the same rules. Either the miner is honest and bypassing any nodes is a moot point, or the miner is dishonest and bypassing any nodes causes his blocks to be rejected (e.g. as with double-spends) if he does not control most ~~nodes~~ miners.

^FTFY. The miner that solves a block doesn't give a rat's ass about what other nodes think. His interest is to have the next miner to solve a block to build on the chain he already extended. Period. This is fundamental.

Okay, you can keep thinking that nodes don't exist and that hashpower rules all. The miner very much cares what other nodes think, since nodes determine whether to reject his block or not. You seem to believe that the "longest chain" is all the matters... but nodes enforce the longest, valid chain. Doesn't matter how many blocks a miner extends on top of an invalid block. It seems you're incapable of imagining any situation beyond everyday orphaned blocks. But we're talking about potential attack vectors and contentious hard forks here.

Quote from: jbreher on February 17, 2016, 05:18:04 AM

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Ignoring hashpower-based attacks, I don't see any basis for your point unless this miner (or mining consortium) controls most nodes on the entire network, or sufficiently clusters Sybils in a given area sufficient to censor or double-spend transactions in that region. If he does not control most of the network, bypassing independent nodes accomplishes nothing.

There you go moving the goalposts again. The proposition under discussion is not whether it is in the interest of any miner to bypass independent nodes, it is that independent nodes add no ability to the network to keep miners in check. I have demonstrated above that there is nothing that independent nodes can do that any given miner cannot route around.

There you go with that misplaced goalposts phrase again. I'll make this one simple (and oversimplified):

Scenario A: 6000 nodes. It would take 6000+ nodes to mount a Sybil attack.
Scenario B: 100 nodes. It would take 100+ nodes to mount a Sybil attack.

Under which scenario are users more secure from attackers (miners or otherwise)? If the existence of nodes makes it more expensive or logistically difficult to mount a Sybil attack, that surely adds to the network's security.

But to hear you tell it, miners will never, ever attack anyone because it's not in their rational self-interest to do so. Roll Eyes

You haven't demonstrated in the slightest that "any given miner" can "route around" any and all nodes.

Quote from: jbreher on February 17, 2016, 05:18:04 AM

A necessary corollary of this is that attempts to maximize independent node count is useless.

Please elaborate.

Quote from: jbreher on February 17, 2016, 05:18:04 AM

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I don't think you've provided a modicum of evidence for #2.

And I don't think you've provided a modicum of evidence against it. I agree, simple reasoning is weak in the face of contrary evidence. Yet, I have not seen any contrary evidence yet - from you or other.

The difference is, I actually addressed this point and provided considerable evidence backing it up. And what did you do? You deleted all of it from your quotes and brushed it under the rug. Speaks volumes.

See near the top of the post, from "I guess you missed the quote below, as you conveniently ignored it."

Quote from: jbreher on February 17, 2016, 05:18:04 AM

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Regarding #3, the utility of, and incentive to run[ning] a node are elusive but not non-existent.

We're not arguing about the incentive for an individual to run a node, we're arguing about whether or not independent nodes add any value to the network. I say no, and I think I've conclusively demonstrated so. I await your rebuttal.

Actually, we were talking about the incentive for an individual to run a node at the time. Likewise, I await your rebuttal.

Quote from: jbreher on February 17, 2016, 05:18:04 AM

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Non-mining nodes are essential to maintaining the integrity and security of the protocol, and many on this forum including myself and David Rabahy above me, can attest to running nodes because we want the system to succeed and/or are invested in its success.

You may be running a node because you want bitcoin to succeed. I think your reasoning is incorrect. As far as David Rabahy, I certainly got the impression that he agreed with me that independent nodes add no value to the network.

I'm running nodes to keep the network decentralized.

Quote from: David Rabahy on February 11, 2016, 03:39:15 AM

Quote from: madjules007 on February 11, 2016, 03:32:36 AM

Logically, hoarders have an incentive to keep the system robust and decentralized -- i.e. running a node, even if not transacting.

Me exactly.

Quote from: jbreher on February 17, 2016, 05:18:04 AM

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But the more you squeeze node operators, the less of us there will be.

While probably true, this is only relevant to #2, and I deny the assertion that doubling storage and bandwidth requirements provides a significant squeeze.

Deny all you want. Any basis for that, or just intuition?