Questions tagged [consensus]

Questions about the consensus system of Bitcoin and the protocol rules that are consensus critical.

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29 views

Mining process in a blockchain

Let's consider a blockchain. They mining nodes are listening to transactions and every one is building is own block. Due to latency and other issues, every miner is probably building a different block,...
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28 views

When exactly do the transactions get validated?

I have some gaps in my understanding to the life cycle of the transaction that I want someone to help me fill them specially with the validation. What I understand about the life cycle with my ...
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28 views

Was it always required for the Coinbase transaction to be the first transaction in a block?

The user tempo mentioned on another topic: "At least in the early protocol versions it was possible to put the coinbase transaction not on the top of the outputs." I have never heard about this ...
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86 views

Can a blockchain's transactions be reversed?

Blockchains are often described as 'immutable' (meaning the history cannot be rewritten after the fact), but is this really true? How easy is it to change the history? I have read about the Etheruem ...
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1answer
34 views

Could a malicious attacker subvert the Bitcoin network by failing to create a block?

I know its astronomically improbable, but say a malicious node "wins" the proof of work inherent to the Bitcoin protocol. If a malicious node simply waited indefinitely, or maliciously disconnected ...
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20 views

Can you call PoW 2f resilient?

Can you call PoW 2f resilient if all nodes would have same hash power? PoW is called eventually consistence. Even in an asynchronous network. The only attack possible is 51% attack. Further, there is ...
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30 views

Bitcoin consensus and server of miners

I know consensus is what 51% thinking.My questions is where miners communicated?On what server,what port??Where??The must push own api (copy of blocks) for thinking of consensus.So where BTC miners ...
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3answers
71 views

What is “consensus”?

I’m really struggling to get my head around a particular piece of lingo in the bitcoin/blockchain space, and would really appreciate if someone was able to give a bit of clarity. I have been doing a ...
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17 views

The time when the miner get a new block [duplicate]

I am wondering the time when get a reward for new mined block. Theoretically, miner will earn reward when they mine new block. but at that time, there is no way to verify that they really waste hash ...
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1answer
85 views

Consensius algorithm difference to PoW and BFT

I have a question on the consensus algorithms, in particular, what is the principal difference conceptual to the family algorithm od PoW(used to bitcoin) and BFT(used to Libra blockchain with the ...
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28 views

How to detect a consensus is BFT or not? [closed]

Can we divide consensus algorithms into BFT (Byzantine Fault Tolerant) and non-BFT ? If so, How to detect a consensus is BFT or non-BFT ? Is there any non-BFT consensus algorithm example ?
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174 views

What is the difference between BFT and PBFT

What are the differences between BFT and PBFT? I want to know the difference between these two concepts. If there is any improvement in the BFT's limitations, let me know. Please answer. Thank you.
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Do Full Nodes validate all transactions and make new blocks after all bitcoin are mined?

Do Full Nodes validate all transactions after all bitcoin are mined? A fork of bitcoin core with all coins pre mined would be behaving in this way too I'd imagine..? Also, would these nodes still ...
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106 views

How does the 51 percent or 2/3 majority voting rule work?

For a block to be added to the chain, it needs vote from majority of miners, is that correct? If yes, does that mean a single block gets worked upon by all of the miners?
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24 views

Proof-of-Stake: What if a bad enactor is chosen by random?

My understanding of proof-of-stake is the following: The node that mines the next block is chosen, randomly in proportion to the amount of nodes they have in the network (ex. person who who owns 5% ...
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1answer
28 views

How do nodes come to consensus on whether a timestamp is valid?

From bitcoin wiki: A timestamp is accepted as valid if it is greater than the median timestamp of previous 11 blocks, and less than the network-adjusted time + 2 hours. If a miner submits a block ...
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32 views

PBFT vs. Proof-of-Authority?

based on this answer: https://bitcoin.stackexchange.com/a/79402/41513 : PBFT (Practical Byzantine Fault Tolerance) is a voting based consensus algorithm in which every node must send messages to ...
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1answer
52 views

What are the biggest Proof-of-Stake roadblocks? [closed]

What are the biggest hurdles (technological or otherwise) that the Proof-of-Stake consensus algorithm must overcome to become the de facto consensus algorithm for blockchain? Or put differently, what'...
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24 views

What is meant with 'the highest PoW'?

What is meant when the nodes select the chain with the highest cumulated PoW? How is the highest highest PoW calculated? I thought the concept itself is called PoW.
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Activation of SegWit v1

The segregated witness soft fork of August 2017 included a versioning field which would allow for future incrementation. Anthony Towns has recently posted an early draft of the proposal for the SegWit ...
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1answer
39 views

Ripple: Validators

All the validators need to reach consensus in ripple. Would it that mean that, the more validators there are, the slower the process results? But the less validators there are, the more unsafe the ...
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2answers
46 views

Does a Node connect to all the peers?

Does a Node connect to all the peers in the network? Or just a few? If its just a few, how many? If its just a few, what about if all of those nodes in the list are malicious?
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1answer
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Blockchain: How do nodes know what Data is correct from Consensus process?

How do nodes know what data is correct from consensus? What about if two nodes execute two different consensus with 2 different Valid blocks with the same height at the same time, can that happen? ...
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1answer
25 views

as a individual miner's side, how UASF, UAHF agree or disagree is occurred?

UASF is timestamp-based method. after that time, new rules will start. but i have a few question about this. how this rules is accepted by USER? does miner program contains 'yes' or 'no' about this ...
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Does everything of a Blockchain Network rely on its underlying “Consensus Protocol”?

I have been reading about and researching on Blockchain Technology for quite a while now, and what I can comprehend from the very primitive architecture of these "Distributed Databases" is that ...
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25 views

How is the fault tolerance measured?

“If the number of nodes that agree exceeds 2/3, the blocks or transactions of clients will be accepted” Practical Byzantine fault tolerance (pBFT) : (n - 1) / 3 I read those 2 things in a PDF that a ...
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Byzantine Fault Tolerant - what a benefit? [duplicate]

According to wiki, if we had m generals, than we need 2m+1 to meet consensus. So it's about 66.6% + 1 generals But what the reason to use consensus like BFT? Why we can't get result of the most (50%...
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Private Blockchains: Blocks’ validation

I’m a software developer and I’m trying to understand blockchain at a code level I have the following issue: There’s a private blockchain, this private blockchain does not have any relation to ...
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41 views

Private Blockchains: Validation

I'm a software developer, and I have some questions about private blockchains, I'd like to have technical answers since I'm trying to understand blockchain at a code level. I'm going to write a ...
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2answers
58 views

Proof for “Is an immutable, decentralized blockchain possible without economical incentives?”

Bitcoin is immutable because of economical incentives. Those who are able to 51% the network can't do it, because it'll result in the value of the currency to drop tremendously, which causes waste of ...
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26 views

Bitcoin Pluggable Consensus with Algorand? [closed]

Algorand is an extremely promising consensus protocol -- Could Bitcoin be configured to use Algorand?
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55 views

On blockchain scalability bottleneck

It is often said that the major bottleneck of blockchain scalability is that every (honest) node has to process every (valid) transactions. But the progress of a blockchain is how fast it reaches ...
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248 views

Did the introduction of VerifyScript cause a backwards incompatible change to consensus?

My question is about the changes to bitcoin done by commit range [a75560d8, 6ff5f718], and their effect on consensus. Out of this range of four commits (all attributed to satoshi) during the dates ...
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42 views

Why is PoW 51% attack resistant?

I was trying to understand why PoW makes the blockchain 51% attack resistant. From my understanding, we can think of PoW as a way to assign a leader who would decide what the next block is. I can see ...
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What is the best way to test new consensus protocol?

I wanted to test a new consensus protocol. However, the bitcoin core is a large codebase (>100k lines). Is there any small codebase which is designed to test new consensus protocols and includes only ...
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1answer
67 views

In what way does Spectre have “weak” liveness?

In his article The Spectre Protocol, Aviv Zohar, one of Spectre's authors, mentions that Spectre has weak liveness. Why does he mention that Spectre has "weak" liveness, and how would "strong liveness"...
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2answers
415 views

Exact definition of “Liveness” and “Safety” properties in a consensus?

Two main properties of a consensus are "Liveness" and "Safety". What are the exact and precised definition of "Liveness" and "Safety" properties in a consensus ? Are the following definitions ...
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1answer
60 views

Is there a max number of tx outputs allowed by consensus? [duplicate]

It seems good for preventing an UTXO bloat by restricting max number of outputs of TX(or block) can have. Is there such a restriction? if there is, which part of source code should I read? If not, why ...
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1answer
35 views

Does the BFT solution from lamport guarantee liveness?

Solution: https://people.eecs.berkeley.edu/~luca/cs174/byzantine.pdf Although there is a lot of material about this, I am still not sure what the answer is. I found two different statements: Yes, it ...
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1answer
57 views

Bitcoin economic nodes, concensus, and historical nodes

With regards to the recent dos + inflation bug, and seeing that most nodes on the network have still not upgraded with the patch (lukedashjr's chart here: https://luke.dashjr.org/programs/bitcoin/...
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1answer
233 views

Byzantine Fault Tolerance Threshold of Bitcoin: 1/2 or 1/3? (Edited)

According to this answer: https://bitcoin.stackexchange.com/a/58908/41513 a Byzantine Fault Tolerant (BFT) consensus threshold is 1/3. On the other hand, there is a common belief that Bitcoin network ...
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2answers
75 views

Do miners become temporary dictators of blocks they mined?

This is something I've read here: https://blockgeeks.com/guides/bitcoin-forks-guide/ "When a group of miners discovers and mine a new block, they become temporary dictators of that block" Can anyone ...
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2answers
311 views

Why didn't Bitcoin implement segwit in the first place?

Why didn't Bitcoin implement segwit in the first place? Why and how does non-segwit Bitcoin enable a miner to change a transaction's txid? From Mastering Bitcoin ch. 7 § "Transaction identifiers": ...
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3answers
270 views

Game Theory in Blockchain?

The blockchain consensus seems to be very related to the Game Theory, when each participant tries to achieve their "favorites", where defining "what favorites means" is not very easy, since a ...
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1answer
96 views

Tendermint consensus: Are validators “known” and “pre-selected”?

What are similarities and differences between Tendermint consensus and Proof-of-Stak? For example, in both consensus, a validator is selected randomly (I think in Tendermint consensus they are ...
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1answer
27 views

Bitcoin version conundrum

Given that the Bitcoin node software not centrally controlled (auto updated) and many different versions and implementations exist around the world, how would a core change be possible if it is not ...
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1answer
248 views

Is PBFT a consensus algorithm?

Can we consider PBFT (Practical Byzantine Fault Tolerance) as a consensus algorithm ? And if yes, How does it work? And is it similar to other consensuses such as PoW, PoS or PoA ? Or it is totally ...
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1answer
228 views

Is “Proof-of-work” a subset of “Byzantine fault tolerance (BFT)”?

Can we say that Proof-of-work is a type of Byzantine fault tolerance (BFT) ? In other words, is PoW a subset of BFT ? Or they are two different categories? Please note that there is a similar ...
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65 views

Consensus roles for op_return

What is the validation rule, not policy, for op_return? What is the maximum length of the data that can be attached? Is it 514 bytes? As if the maximum script size was 520 bytes -1 byte for the ...
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1answer
159 views

How to select a leader in RAFT consensus protocol [closed]

Suppose a network of 5 nodes uses RAFT consensus protocol. Each nodes maintains a transactions log which consists of a list of the log entries. Each log entry again consists of index and term. All of ...