Questions tagged [proof-of-work]

This tag should be used for questions regarding how Proof of Work works and Proof of Work algorithms. Proof of Work is a scheme where a 3rd party can verify that someone performed at least a certain amount of work to produce something. This is used in Bitcoin mining.

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31 views

Chain Race: How to know chain-length of competing chain?

If a fork happens, miners mine on the block they receive at first. Further, they only forward the block they received first (so the block they will use to mine)! So it can happen that 10% of the ...
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Why is proof-of-work required in Bitcoin?

It seems that the rationale behind the proof-of-work requirement in Bitcoin is that it creates trust in a decentralized trustless network by: helping to reach consensus on which version of the ...
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Beneficial proofs of work [duplicate]

I'm new to this community and a Bitcoin novice. I believe to have understood the concept and purpose of proof of work but also, that the high energy consumption of proofs of work is a major problem ...
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144 views

Hash-based crypto-currencies?

What are the most famous crypto-currencies which use repeated hashes as proof-of-work? What are the other proof-of-work methods?
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Does proof-of-work contribute directly to prevent double-spending?

I know similar questions have been asked before (e.g. How proof of work prevents double spend) but I'm struggling to visualise the solution to double-spending being directly reliant on proof of work. ...
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30 views

Mining operation calculation

My goal is to understand bitcoin. I have read what happens during a transaction and have a question about it: When a transaction happen, the miners compute a value called "prof of work". This value ...
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2answers
94 views

What would happen if miners refused halving

In may 2020 the supply of bitcoin per block is supposed to be reduced by half https://www.bitcoinblockhalf.com/ What if after this phase the first miner or more than 51% of them decide to keep the ...
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184 views

Difference between Hashcash proof of work algorithm and Ethash proof of work algorithm?

Understand that each proof of work algorithm has its pros and cons. Difference between Hashcash proof of work algorithm and Ethash proof of work algorithm? Nathan Aw
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What Value does mining provide?

After reading the O'Reilly book and perusing online resources, I'm still confused about the value that the actual mathematical mining provides to Network (I understand it does provide value, but not ...
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2answers
278 views

Why can't miners meet the difficulty by picking a low number for the block hash?

In terms of 'proof of work' my novice understanding is that miners are tying to come up with a 64-digit hexadecimal number, "hash," that is less than or equal to the target hash. Can't miners always ...
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35 views

What is stopping me from modifying the mempool of my node (may it be PoS or PoW)?

I have been trying to wrap my head around some core concepts of how a blockchain works and something has been bothering me for a while. Let's consider a case where I am running a full node of a ...
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Why is the winner of Pow different everytime?

I just read about how miners have to change the nonce bit in order to find an hash below a certain result. Granted each miner process it the same way, incrementally, adding 1 and hashing, adding one ...
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A question about Proof-of-Work(PoW)

I will describe my question using an example. Let's say the network is working on adding block #100 to the blockchain. An attacker recreates block #99 with a combination of transactions that are "...
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33 views

Timer-based consensus algorithm in blockchain

Assume that there is an algorithm that ensures: 1- That a full node chooses an honest random wait time. 2- That the same node has waited the specified amount of time before proceeding to mine a block. ...
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182 views

Is the purpose of proof-of-work the immutability of the blockchain?

I have a disagreement with a person: I believe that the primary and most important goal of including proof-of-work (and therefore the nonce) in a block is to make it hard for an attacker to change ...
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55 views

Mining Probability

Assuming two miners have a (1/x) chance of finding a block over some time period, is the probability of both miners finding a block within that period simply (1/x^2)? More generally, would n miners ...
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Is Bitcoin PoW actually SHA256 + Merkle generation? Or have I misunderstood coinbase/append?

Miners can mutate nonce (32 bits) + time (mutates once a second). This allows for 232 (~4 billion) hashes per second. That's not enough anymore for our ASICs as they perform in the TH/s now rather ...
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590 views

How does a mix between Proof of Work/Stake work? (Peercoin)

I think I understand Proof of Stake and Proof of Work from a conceptual point now. For themselves both are good ideas for sure, but how would a crypto currency like Peercoin (PPC) combine both of them?...
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60 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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PoW 51% attack vs. BFT 1/3 attack?

So from what I understand, Bitcoin's PoW is prone to 51% attack, but as a distributed system it is also prone to BFT's 1/3 attack right? I think it's mathematically proven that in a distributed system,...
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Finding target based on difficulty calculation

I'm trying to find the current target value, but it is not listed in any place. So far I found out that the only way to get target value is to calculate it from "difficulty" value, which is now: 6,379,...
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32 views

Estimating difficulty of “Memory-Hard Proof-of-Work” based on “size of memory”?

In Bitcoin proof-of-work, the difficulty of Proof-of-Work is estimated and calculated based on total hashing power of the participants. If total hashing power of the participants is higher, then PoW ...
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How does proof of work inspire trust when the work is just guessing?

I'm struggling to understand the value added by machines guessing at inputs to create a hash below a target value in order to produce a proof of work. I understand the proof of work is somehow ...
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1answer
215 views

How does Proof of Stake prevents dishonest behaviour compared to PoW?

I know that in Proof of Work (PoW) once a node has found the solution (the nonce) they announce it to the network. Then the rest of the nodes can easily verify the correctness of the block hash and ...
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1answer
136 views

Why do we need to chain the blocks (creating blockchain) in a permissioned blockchain?

The main question is: What does "chaining block" mean in a permissioned blockchain? OR in any blockchain network in which creating a new block does NOT need consuming resources/energy ? (even in the ...
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How do blockchains in each nodes maintain consistency?

What I understand as (Please correct me if any statement is wrong) Every full node tries to generate a new block, in which different amount of transactions are included and what to be included will ...
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2answers
38 views

How do bitcoin miners determine the next valid state of a ledger?

I know bitcoin miners compete for a reward by seeing who can solve a difficult hashing problem first (proof-of-work). However, how does this random hash problem help validate the transactions in the ...
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How to change Bitcoin's proof of work? Then enable miner [closed]

I'm using https://github.com/jgarzik/pyminer/blob/master/pyminer.py to test a few different hash functions. Instead, I'd like to try keccak, a few of them in some order like an "X5" and so on. This ...
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1answer
40 views

When does miner insert the coinbase transaction?

When a miner creates the candidate block with transactions from the mempool, does he insert the coinbase transaction after winning the PoW or during PoW?
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How to model randomness in validators selection in PoS?

I searched a lot here and on the Internet to figure how how randomness selection of validators in PoS works? I understand it is a random selection based on fraction of stake a validator has, similar ...
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2answers
472 views

Proof of work - lottery approach

I'm sure I am missing something here. But not sure what ... Proof of work - after all is said and done, when a hash is found (about 10 min), it is said to be like someone hitting the lottery. Anyone ...
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77 views

What is entropy mean in this context?

"The Bitcoin nonce forms part of the block header, which is used by miners to provide entropy as part of the Proof of Work process, to try and find a hash meeting the difficulty requirement." Quote ...
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1answer
200 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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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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109 views

Permissioned or Permissionless blockchain? Which one is PoS more adapted for?

Since in proof-of-stake (PoS) there is no mining process, according to functionality of permissioned and permissionless blockchains, which type is PoS more adapted for? In the other words, is a PoS-...
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73 views

where in the source code is the the proof of work checking the blockheader hash and nonce?

Where in the source code do we check whether hash(blockheader*nonce) < Difficulty In fact, the line I found is as follows: https://github.com/bitcoin/bitcoin/blob/v0.17.0.1/src/pow.cpp#L87 My ...
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45 views

If all Proof of … systems use mining

I understand how Proof of Work (PoW) works now, and am beginning to look at different Proof of ... systems like these: Proof of Stake Proof of Ownership Proof of Existence Proof of Space From what I ...
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Proof-of-Stake: How to ensure immutability of the blockchain?

In Proof-of-Work, a miner tries to solve PoW puzzle based on the hash of previous block, such that in case of changing block B_i, all blocks after that (blocks B_i+1, B_i+2, ...) are no longer valid ...
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20 views

Is it possible to accurately map hashing power to network size?

Let's say we have a network with n nodes in it. Is it possible, when the hashing power of the network is calculated after a proof-of-work, to accurately estimate n with an algorithm taking the ...
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What's the difference between PoW and PoS?

I'm looking for an explanation of the difference between Proof of Work algorithm and the Proof of Stake and how they relate to Bitcoin and the Blockchain. Also looking for a fairly simple, non-...
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81 views

group proof of work

Right now, every node in a Proof of Work system, solves the POW puzzle independently. Is there any concept of group proof of work, where everyone in the group needs to solve part of the puzzle.
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Who decides what the next, correct Nonce is?

As I understand finding the correct Nonce is the basis when hashing transactions for Proof of Work. How and where is this decided in the ecosystem what the next Nonce is? In my limited understanding ...
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1answer
147 views

What hash algorithm is used in Bitcoin Cash?

I know that bitcoin uses hashcash as PoW algorithm, Ethereum uses EtHash and Litecoin uses Scrypt. But I didn't found anywhere the PoW algorithm used in BitCoin Cash, does it uses hashcash too?
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The bitcoin mining algorithm from a programmer's viewpoint

This page: Blocks said mining is actually to solve a mathematical problem, but reading Block hashing algorithm doesn't give much help. I also tried reading bitcoind source code, but reading code takes ...
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1answer
613 views

Where can i find proof of work in bitcoin core source code?

does anyone knows which part of the bitcoin core source code contains the proof of work for mining, creating of block and adding to blockchain? what are the files and functions involves? https://...
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4answers
112 views

Use of proof of work in bitcoin

I am trying to understand what problem in bitcoin proof of work solves and came to this somewhat helpful quote: So, for instance, if a miner controls one percent of the computing power being used ...
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1answer
93 views

What is the “main” difference between consensus mechanism of Bitcoin and Ethereum?

Bitcoin and Ethereum both use proof-of-work (PoW) consensus mechanism. One of differences between Bitcoin Pow and Ethereum PoW is difficulty level, meaning that while in bitcoin block generation rate ...
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is the proof-of-work for safety or efficiency?

i am reading the proof-of-work (aka: pow, target threshold, difficulty, etc.); my understanding is that pow adds a requirement to validate block headers, so that both benign and malign nodes need a ...
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What exactly is Mining?

I have heard that mining is for people with ready hardware and blah blah blah... But what exactly is it? Does it operate like real mining? I mean, people talk about it like you are physically mining.
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91 views

Partial Proof of Work in Pools

Technically speaking a full PoW solution is one whose hash value is below a certain threshold value say V. It is not equivalent to saying that the hash value must begin with say X number of zeros (...