Topic: DECENTRALIZED crypto currency (including Bitcoin) is a delusion (any solutions?) - page 39. (Read 91110 times)

If you making mining unprofitable, won't you lose the honest miner's incentive to win the block reward rather than to double spend?

Because they want to send a transaction to the block chain.

TPTB_need_war, why would anybody secure your currency if mining is unprofitable?

Added these to the upthread PoS post:

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After eating most of blood flow to the stomach leaving less oxygen for the brain. Are you sure you can "single-handedly" analyze those posts?

You think it is professor JorgeStolfi?

Perhaps due to the academic knowledge displayed but I doubt he would be afraid.

I need to eat first and then catch up on the latest posts in this thread.

I completely agree that it is theoretically impossible, however that's not what I'm asking.

Total sequence is impossible. Say one node A is in New York, and node B is in Sydney. both measure data of one variable and broadcast message over the Internet.

A observes the timeseries, +3, +1, +5
B observes the timeseries, +1, +5, +3

Node in New York will observe all messages from A first, then B. Another different node in Paris might observe in mixed order:

e.g. +1 (B), +3 (A), +5 (B), +1 (A), +3 (B), +5 (A).

All nodes can agree on a partial order, with subject to some constraints. How to achieve total order nobody has clearly described.

It gets very interesting and complicated if one attempts to model a program as a flow of messages over a network.


double spending for partial order order is solved. it might be that PoW is not 100% fair or efficient, but no doubt it does work to some extent.

Total order of events is unsolved. I don't see how trees, DAG's, or anything else can even address the problem. One would always need to trust nodes which are closest to the source of events. Only the node which broadcasts the message will know the ultimate truth.

Aye, the same is observed in general theory of relativity

Agreed. The analogy is that with one transaction per block, two blocks referencing the same parent represent a partial ordering equivalent to two transaction within the same block.

However, getting back to my original question above; do you agree that a partial ordering is a strictly weaker requirement than a total ordering, which would, indeed be 'enough' to solve the problem of a trustless consensus?

(https://bitcointalksearch.org/topic/m.13581964)

Blockchains allow for partial order and eventual consistency. Not all nodes agree on everything. In particular in Bitcoin they don't agree whether transaction A happened before transaction B (total order of events). Double spend problem means one can order transaction in packages called blocks. Blockchains implement partial order of events. That's also why script is Turing non complete.

More formally, one can sort transactions (or events or messages) by time the way Lamport did. So its mathematically a partially ordered set, i.e. a relation of a set of events (transactions are events or messages). The relation can deliver an answer for 2 events A and B and determine whether event A happened strictly before, strictly after, or roughly at the same time (in one block). What makes it even more complicated is that Bitcoin has a statistical distribution. The longer in the past A and B the more sure one is, since more nodes have confirmed it.

To have a total order of events, I think nobody has even an approximation. Two nodes will always disagree on total order, the same way two people in the same room will always see something different if they are in different locations. But they might agree enough.

I don't think one transaction per block would solve that problem. I believe its impossible to implement total order or anything like it, without a actually distributed timestamp mechanism. One can imagine a system where all computers connected to the Internet at the carrier level also have a timestamp protocol. If carriers are trustworthy (a very big ask), then everyone could look up the timestamp for a message. TCP/IP packets are not timestamped on top level and no entity on the Internet holds a history of events on the protocol level (everything refers to only the current state).

A good reference for these things is also the work of Carl Hewitt: https://en.wikipedia.org/wiki/Carl_Hewitt . He invented messaging with actors and wrote about eventual consistency.

And if you allowed only one transaction per block?

edit: The partial ordering can only be within one single block, and the total ordering is of all blocks, so if you have only one transaction per block, doesn't it follow that you have a total ordering of transactions?

A system based on math does not agree to your conclusions.. It either works or doesnt for all cases. That is what btc to the stage as ideal money

?

Go back a page, and you will find the answer.

wonder who the new user really is.. scared that he will lose the argument? why do ppl hide behind nicknames?

You are right. Even more, some percent of double-spendings can be tolerated if we save a lot of resources by allowing this. Every day new counterfeit dollars appear in the streets but Earth doesn't stop spinning. If we accept that it's fine for FED to print more money, why a skilled guy from Harlem can't do the same? Hell, I would prefer the latter, at least he can't print that many banknotes.

CAP does not apply to distributed systems. Sure, state can be inconsistent, but that's not necessarily a problem. Consistency is usually over-rated by academics, and that's how one often ends up with misleading theorems. Any two computers communicating over a distance will be out of sync. The basis of blockchains is Lamport's work on how communication can happen in such a distributed system. In essence there needs to be consensus on a partial order of events. Total consensus on one variable is impossible, since information can't travel faster than light, but it is not required. If node A knows that X = 1, he sends a message to B "X = 1". But it might be that before that message reaches B, that X = 2. This in itself is not a problem. Bitcoin's PoW indeed solves the double-spending problem. Its possible even at a distance to know what happens first, as long as Peers are honest (if A sends message X = 3, although X=1, the result will be false in any case independent of the order). Say in Bitcoin everyone knows that Alice owns 1 BTC. If she sends a message to all peers, that she wishes to transfer her wealth to Mallory, then this message will only be applied after a rather long interval - the block cycle. Blockchains doesn't mean that all nodes agree on a total order of events. It means consensus on partial order of events. The most important article for understanding blockchains very few seem to have read and understood is: http://research.microsoft.com/en-us/um/people/lamport/pubs/time-clocks.pdf . Lamport also came up later with the Byzantine Generals problem.

This is not specifically about trees; it could be any single, completely linear sequence of chained transactions. In fact, I think the reader would be enlightened by the answer to this simple, direction question about trustless consensus:

Why is it not enough to find one global sequence for all transactions ever made?

As I see it, sequencing is all you need, even in the face of double spends because the first time an output is spent in this linear sequence, subsequent spends of the same output will simply be invalid.