Bitcoin as Global Truth

I should expand on something that I said earlier:

Quote from: nullius on March 26, 2021, 09:39:02 AM

The Bitcoin ledger is a single global truth.

The phrase “global truth” was not intended as an ideological statement. A monetary system perforce requires that if Alice makes two transactions doubly-spending the same coin to Bob and to Charlie, then there must emerge a single global truth about who gets the money. Otherwise, the money is worthless: Who wants money that 99.9% of people believe you have, and 0.1% of people believe really belongs to someone else?

A useful lay definition: The Bitcoin consensus is a single global truth of who has what money at each point in time. The truth must be absolutist, with zero tolerance for any deviations: Either Bob has the coin, or Charlie has the coin—either-or, with no room for any disagreement.

Bitcoin achieves a single, global, unanimous Consensus of absolute Truth, even in the face of Byzantine faults—although it does so probabilistically. In the above example, as the number of confirmations of the winning transaction increases, the probability approaches 1 that absolutely 100% of honest nodes will reach the same conclusion about who has the coin—either Bob, or Charlie. And each additional confirmation exponentially increases the security of this automagical unanimous agreement. Satoshi knew this; see §11 of the Bitcoin whitepaper.

In the context of Bitcoin, that is the meaning of “consensus”. And...

Quote from: nullius on March 26, 2021, 09:39:02 AM

Mutually untrusting nodes agree on this one truth, with no central authority to call the shots or enforce rules.

Bitcoin reaches this Truth with no central authority: Nobody in the world has an override button for ruling in favour of Charlie over Bob, or vice versa.

Quote from: d5000 on April 02, 2021, 08:51:53 PM

Quote from: nullius on March 26, 2021, 09:39:02 AM

There is hereby a failure of human language usage: The word “consensus” is overloaded.

In Bitcoin, the word “consensus” has the very specific technical meaning. It does not refer to an agreement amongst humans, as in colloquial usage. Rather, it denotes the resolution of a synchronized state in a distributed system.[...]

In Bitcoin, the consensus means that all nodes arrive at the exact same conclusions about the current global state of the blockchain ledger: The set of valid transactions that exist, the meaning of each of those transactions, and the order of those transactions.

You are of course right, the usage of the word in this thread is a bit ambiguous/imprecise, mixing the "colloquial" with the "technical" meaning, but I think nevertheless the discussion here has to do with consensus.

Much mischief is done by the ambiguity of overloaded words. Another example is “entropy”. The word “entropy” has multiple distinct technical meanings in multiple fields, and multiple distinct meanings within the fields related to cryptography; if you confuse different types of “entropy”, then you will break your random number generator.

You understand the distinction here, but I think I really need to drive the point home for the public benefit:

In the context of Bitcoin, “consensus” is not how people agree to the rules, but how nodes agree on a global state based on the rules that everyone already agreed to. This is not simply my opinion: It is the meaning of the word “consensus” in the context of distributed systems architecture.

Compare and contrast the problem formulation in this excellent paper:

Quote from: Heidi Howard, Richard Mortier. “A Generalised Solution to Distributed Consensus” https://arxiv.org/abs/1902.06776

Problem definition

The classic formulation of consensus considers how to decide upon a single value in a distributed system. This seemingly simple problem is made non-trivial by the weak assumptions made about the underlying system: we assume only that the algorithm is correctly executed (i.e., the non-Byzantine model). We do not assume that participants are either reliable or synchronous. Participants may operate at arbitrary speeds and messages may be arbitrarily delayed.

We consider systems comprised of two types of participant: servers, which store the value, and clients, which read/write the value. Clients take as input a value to be written and produce as output the value decided by the system. Messages may only be exchanged between clients and servers and we assume that the set of participants, servers and clients, is fixed and known to the clients.

An algorithm solves consensus if it satisfies the following three requirements:

Non-triviality. All output values must have been the input value of a client.
Agreement. All clients that output a value must output the same value.
Progress. All clients must eventually output a value if the system is reliable and synchronous for a sufficient period.

The words “servers” and “clients” must be adapted to the context of a P2P network. The portions highlighted in pink do not apply to Bitcoin. Bitcoin is designed on the Byzantine model. Also, it arguably does not guarantee progress.

Quote from: d5000 on April 02, 2021, 08:51:53 PM

The "global state" of the blockchain can be altered only following the strict rules of the Bitcoin protocol. [...]

Indeed.

Quote from: d5000 on April 02, 2021, 08:51:53 PM

But maybe here we shouldn't talk about "the consensus" but about "protocol rules" or "consensus rules", or "how consensus rules are established".

Good idea.

Quote from: Metal Brain on Today at 01:17:58 PM

A previous poster on here said the NSA created the backbone of the bitcoin network with backdoor vulnerabilities. Perhaps they don't need to go through the expense of a 51% attack. They can pull the plug whenever they want. Heck, the establishment probably created it and own most of the bitcoin and are just doing a big pump and dump scheme.

Are you sure that “a previous poster” isn’t you? Roll Eyes

You created your account after that “previous poster’s” first crap on this thread had been ignored for almost two days. You bumped it, then started spreading more crap in the guise of asking questions. You have only posted on this thread. Now, you are not-so-subtly calling attention to utter crap from “a previous poster”—and in the same breath, you have overtly started to parrot the “previous poster’s” party line. I think that I can call this one.

Quote from: DooMAD on April 20, 2021, 11:52:25 AM

Quote from: pooya87 on April 20, 2021, 06:09:11 AM

Quote from: btc-room101 on April 18, 2021, 12:20:37 PM

of course NSA could crack this stuff all along.

Any proof or is it just the tinfoil hat talking?

Pretty sure that applies to every post this user has ever made. I don't think I've ever witnessed them utter a word of sense in all 294 posts.

Pretty sure he’s trolling. Like posting a comment about Microsoft Linux on Slashdot in 1999, and waiting for a dozen people to correct that in gruesome detail.

Or on second thought, he looks like a scammer...

Anyway, he predicted that SHA-256 would be broken by 2020; so take his nonsense for what it’s worth. 🗑️

Quote from: btc-room101 on April 18, 2021, 12:20:37 PM

quantum-computers are way off, but 2^256 will be cracked soon with off the shelf hw.

Quote from: btc-room101 on Today at 07:46:34 AM

The so called block-chain, is just what we call a linked-list in computer science, 70 year old tech nowadays.

Yup, grade F transparent troll. Yawn. He may have better luck spreading rumours that nullius works for the NSA.

(From my desk in Fort Meade.)