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Proof-Of-Work is a Decentralized Clock

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Re: Proof-Of-Work is a Decentralized Clock

#91

Post by mrb »

rocqua wrote: post #30

I think some of this is kind of wrong. Mostly the claim that "The Difficulty is Intergalactic" is just flat wrong. Consider a miner on mars with 10% of the hash-rate on earth. Lets say the light delay from earth to mars is 10 minutes (it is 14 on average). Now, suppose mars has last seen block B_0 and it was mined on earth (as would happen most often due to 90% of the hash rate being there). We will call E_1 the next…

«for sha-256 using brute force, this probability is totally 0»

It's not zero. It's very small, but not zero. The difference between being "theoretically exactly zero" and "very small" (yet practically zero) is why we can say SHA-256 is memoryless.

Re: Proof-Of-Work is a Decentralized Clock

#92

Post by icebraining »

incompatible wrote: post #63
icebraining wrote: post #41

Earlier quoted context omitted.

Intuitively, for two planets, I'd say you need the delay to be inside (some percentile of) the variation between the time taken by each block, so that a planet has the chance to "leap ahead" of the other. So if a block takes X minutes with a 20% variation at, say, 95th percentile, and the inter-planet latency is 10 minutes, then I think the target time (X) must be more than 100 minutes, so that if Earth mined the las…

Earth would presumably still have the majority of the miners, so once they'd found a block they'd have a consensus. They'd ignore a block received from Mars that didn't build on that block. Mars wouldn't be able to do the same to Earth.

Right, the majority of time, that's what would happen. But sometimes, Earth would mine a block, send it to Mars and immediately start working on the next one, and yet Mars would win it simply because they got lucky enough to find the solution first, despite having a 20m handicap. And then Earth would have to get lucky (which would be easier, since they have more miners, but that's OK).

My idea is just that if you increase the target time quite a bit, Mars would get lucky more often.

In fact, this already happens: if an European miner wins a block, then why don't other European miners always win the subsequent blocks, since their latency to the winner is lower than American or Chinese miners? It's because the few miliseconds extra are not relevant when a block takes 10m on average to find.

My idea is just to increase the target time so that the 20mins latency are also not relevant.

Re: Proof-Of-Work is a Decentralized Clock

#93

Post by omarforgotpwd »

rocqua wrote: post #19

> The Bitcoin Difficulty adjusts dynamically so that a proper hash is found on average once every ten minutes. So here, the bitcoin network needs to defer to the actual time. The difficulty is adjusted every 2016 blocks. Then, the time it took to create those blocks is determined by looking at actual time stamps of the blocks. That is, time stamps that purport to be the time in UTC when the block was created. I never…

First of all the difficulty doesn't need to be set perfectly. It just can't be way too high or way too low. Even if the algorithm is slightly off the optimal difficulty everything still works fine. Secondly, because other nodes need to validate the submitted blocks for the miners get any reward they are strongly incentivized to fill out all the information in the block as correctly as possible, including the time. Imagine mining a block and getting a 12.5 BTC reward (currently valued at around $100,000) and having it get rejected because you put the wrong timestamps -- ouch. I don't know what logic they use to see if the timestamp is valid, but even if there was a bug in this logic that was used for nefarious purposes other peers would wise up and patch the software if it hurt anyone in any way. So yes, the difficulty calculation may not be perfect and could even be subject to manipulation but it seems good enough for now to me.

Re: Proof-Of-Work is a Decentralized Clock

#94

Post by [deleted] »

state_less wrote: post #66
danbruc wrote: post #58

Earlier quoted context omitted.

The problem is, where do your coins come from? Who or what is allowed to bring coins into existence and what prevents them from just creating as many as they like? The second problem is, how do you resolve conflicting transactions spending the same coins?

There wouldn't be any coins, instead double entry accounting I (pubkey:ae32...) owe (pubkey:af41...) 10 US dollars. Medium of exchange is agreed upon by the two parties, USD is one option. If you're my friend or a business, and you see my balance is deeply negative, maybe you don't give some service. If your my friend or a business, and my credit is not too bad, you follow my repo and give me some service. You commit…

[deleted]

Re: Proof-Of-Work is a Decentralized Clock

#95

Post by jacobush »

gruez wrote: post #35
rocqua wrote: post #33

Earlier quoted context omitted.

Is there a way to use clock drift to exclude certain miners? That is, change the time-stamp in such a way that honest miners using an actual time-stamp might get their blocks denied?

you can already exclude certain miners by not building ontop of their blocks.

Yes, but that shut the question down. There may be interesting nuances left to discover. If we do as you suggested, we would actively "attack" certain miners, quite openly. With a time shift, could miners collude to increase the burden on other miners not privy to the collusion? Perhaps ever so slightly?

Re: Proof-Of-Work is a Decentralized Clock

#96

Post by jacobush »

skybrian wrote: post #79
gtrubetskoy wrote: post #39

Earlier quoted context omitted.

>> Mostly the claim that "The Difficulty is Intergalactic" is just flat wrong. (I wrote the article) - I see your point, but I think the article is still correct. Now communicating the winning block is a problem, as you pointed out, so as a miner on Mars you're at a disadvantage, but that statistically the probability of solving the puzzle remains same regardless of your location in the universe is still true. As som…

While you don't have to report that you failed to calculate a hash, it matters that, had you succeeded, you would have reported it. Someone who calculates hashes with no ability to report them shouldn't count as a participant. To put it another way: if there is a group of participants with spotty Internet that, after succeeding in calculating a hash, have only 10% chance of actually reporting it, then working backwar…

(multiply by zero)

Re: Proof-Of-Work is a Decentralized Clock

#97

Post by jacobush »

incompatible wrote: post #63
icebraining wrote: post #41

Earlier quoted context omitted.

Intuitively, for two planets, I'd say you need the delay to be inside (some percentile of) the variation between the time taken by each block, so that a planet has the chance to "leap ahead" of the other. So if a block takes X minutes with a 20% variation at, say, 95th percentile, and the inter-planet latency is 10 minutes, then I think the target time (X) must be more than 100 minutes, so that if Earth mined the las…

Earth would presumably still have the majority of the miners, so once they'd found a block they'd have a consensus. They'd ignore a block received from Mars that didn't build on that block. Mars wouldn't be able to do the same to Earth.

If we are going to get this paper clip optimizer really started, Earth is not going to cut it. There is much more mining energy to be tapped closer to the Sun.

Re: Proof-Of-Work is a Decentralized Clock

#98

Post by jacobush »

state_less wrote: post #87
danbruc wrote: post #78

Earlier quoted context omitted.

So the entire thing starts with everyone having a balance of zero. Then A signs a transaction that he gives $1000 to B and we broadcast that transaction, new balances A $-1000, B $+1000. Now B wants to buy something for $500 from C and signs a matching transaction. What does C do? Is A a bank that provided a $1000 loan and therefore C will be able to actually get $500 from A? Or are A and B one and the same poor guy…

The important part is A signed over to B $1000. B and C may be the same person. B wanting to do business as C. If A, B and C are all the same person and there wasn't an identity attached to any account, outsiders wouldn't value the record much, especially if they were transactions of significant value. C could redeem the value with Western Union (or similar agent). They might say you have to agree to sign the closure…

"similar plausible deniability as Bitcoin" - not very much, then.

Re: Proof-Of-Work is a Decentralized Clock

#99

Post by hudon »

> There is a separate consensus in a rare but common case of two consecutive ticks being associated with conflicting blocks. The conflict is resolved by what block will be associated with the next tick, rendering one of the disputed blocks “orphan”. How the chain will continue is a matter of chance

It being a "matter of chance" may be false and thus the thesis that this clock is "decentralized" should be questioned. There are situations where there will be conflicting blocks and no block gets orphaned unless a central authority commands it to be so. This was seen in the 2013 Bitcoin fork, when Pieter and Luke ordered the miners to move away from the majority chain (0.8) onto the minority chain (0.7) and this was also seen in 2016 when Vitalik ordered that a permanent chain divergence (ie. fork) happen. In both cases, the blockchain split and a central authority was necessary to resolve the conflict. It was not a matter of chance. The fact that this clock can have permanently divergent chains and that a central authority is required to say which chain should be chosen as the right one means that this clock is not decentralized.

Re: Proof-Of-Work is a Decentralized Clock

#100

Post by icebraining »

state_less wrote: post #87
danbruc wrote: post #78

Earlier quoted context omitted.

So the entire thing starts with everyone having a balance of zero. Then A signs a transaction that he gives $1000 to B and we broadcast that transaction, new balances A $-1000, B $+1000. Now B wants to buy something for $500 from C and signs a matching transaction. What does C do? Is A a bank that provided a $1000 loan and therefore C will be able to actually get $500 from A? Or are A and B one and the same poor guy…

The important part is A signed over to B $1000. B and C may be the same person. B wanting to do business as C. If A, B and C are all the same person and there wasn't an identity attached to any account, outsiders wouldn't value the record much, especially if they were transactions of significant value. C could redeem the value with Western Union (or similar agent). They might say you have to agree to sign the closure…

Thing is, why would Western Union want to buy the debt unless they knew who A is and if they have any hope of collecting from them? This would probably only work if A was a known entity, and generally trusted to have the money they signed over. But if they are, why do we need Western Union at all? Just have C go to A to ask for the money. And if A is an publicly-known entity that exchanges signed amounts for the underlying currency, they're essentially an Exchange.

Combining this, you essentially get GNU Taler: https://taler.net/

No proof-of-work, just a way for people to get digital money (representing USD, gold, or anything else) issued by A (Exchanges). And rather than regular signatories they use blind ones, so that A doesn't even know that B spent its coins on C.

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