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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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1answer
93 views

Can we construct a UTXO which is spendable only via proof of work?

Do the current Bitcoin opcodes and transaction size limit allow constructing a UTXO which is only spendable if a specified amount of work has been performed? So the spender, would provide a nonce as ...
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1answer
140 views

A Blockchain that merges mining forks and could be more power-efficient? [closed]

I'm new to blockchain technology so I'm sorry if I'm using wrong terminology. This is not a Bitcoin question, but a general blockchain question. Imagine a theoretical blockchain that uses gradual ...
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1answer
28 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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3answers
54 views

when a miner solves the problem in less than one timestamp then what does it do with its extra capacity?

If a miner solves the problem in less than one second then how does it use the extra capacity.
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1answer
38 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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1answer
31 views

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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2answers
100 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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2answers
284 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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1answer
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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2answers
1k views

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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6answers
2k views

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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1answer
31 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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1answer
19 views

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 "...
2
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1answer
376 views

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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2answers
63 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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1answer
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. ...
4
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1answer
439 views

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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1answer
68 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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0answers
41 views

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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0answers
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 ...
2
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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 ...
2
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1answer
55 views

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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1answer
85 views

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
42 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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1answer
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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 ...
2
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2answers
475 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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1answer
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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1answer
110 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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1answer
75 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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1answer
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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2answers
82 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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0answers
64 views

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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4answers
2k views

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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2answers
22 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 ...
2
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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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1answer
218 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 ...
0
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1answer
37 views

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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1answer
99 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 (...
2
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1answer
109 views

Is this calculation of mining probability using the Bernoulli trial formula accurate?

I'm trying to understand the formulas for successfully mining a block (without a pool) based on hashrate over time (i.e. to chart the probability of finding a block at various historical points ...
2
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1answer
61 views

Proof of work: average number of tries to create a block

First, I'm sorry if I'm asking a stupid question. I'm just trying to understand bitcoin. I'm reading the Ethereum white paper, and I couldn't understand this sentence about proof of work: At the ...
3
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1answer
85 views

Why haven't a large number of cryptocurrencies copied Primecoin's mining algorithm? [closed]

According to my understanding, generating an ever-growing list of prime numbers benefits mathematics and society in some mysterious way. Given this, why have more recently created proof-of-work ...
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1answer
214 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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1answer
28 views

How is the amount of proof-of-work invested in a chain calculated?

The bitcoin whitepaper (page 3) states The majority decision is represented by the longest chain, which has the greatest proof-of-work effort invested in it. I could not find how exactly this ...
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2answers
78 views

What is the reason to pay miners “monetary rewards” for mining process?

Is it correct to say that: In Bitcoin, it is crucial to incentivize miners by monetary reward, because mining process has significant monetary cost (energy/electricity cost). ? otherwise, mining ...
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3answers
52 views

What is resource of mining rewards

How the coins must be paid miners for mining process is provided? One of resources may be transactions fee. Is there any other resources for proving reward of miners?
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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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2answers
61 views

What would happen if PoW cost were drastically reduced or eliminated?

Assuming Bitcoin had a different method for selecting winning nodes and controlling block time creation, please describe step-by-step how the Bitcoin network would be vulnerable to various attacks. ...
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4answers
827 views

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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1answer
48 views

Ethereum's PoW difficulty

Bitcoin's block time is about 10 minutes while that of Ethereum is 15 secs. Both are using PoW at this moment, right? How come Ethereum's block time is so short compared to Bitcoin? Is hashing a lot ...