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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26 views

Potential fork from genesis block using enourmous computational power

51% attacks are commonly discussed where one entity could potentially mine blocks ahead of the network. The assumption is that the attacker manages to acquire 51% of computational power. However, ...
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107 views

Why can't a 51% attack change past blocks on the blockchain?

I have read that it is not possible to reverse transactions already added to the blockchain but I do not understand why that is not possible in a 51% attack. If an attacker was to change the ...
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1answer
60 views

Making the block reward dependent on the difficulty?

I am looking for papers which discuss, if making the block rewards dependent on the difficulty could be used to curb excessive PoW growth. Idea is that BTC price roughly drives difficulty and energy ...
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2answers
49 views

Bitcoin: How does Proof of Work and single transactions align?

I'm reading papers since hours and still don't get one thing: A bitcoin transaction is an information like "Bob sends 2 BTC to Alice". This message is signed with Bobs private key and needs ...
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16 views

Are many nodes in the network trying to find a proof of work for the same block of transactions? [duplicate]

If two nodes in the bitcoin network receive the same transactions and now both are trying to find a proof of work of the current block, wouldn't this be inefficient? Because presumably both nodes are ...
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1answer
24 views

Appending txns to merkle tree on PoW efficiency, true hash rate

As I understand, when miners add transactions to their candidate block from their mempool, they append the txn to the merkle tree, which requires more hashing, as well as the hashing/maths involved ...
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4answers
1k 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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13answers
11k views

Is there a way to set up proof-of-work systems so they would be even more useful?

One of the arguments made against Bitcoin's design choices is that it wastes resources authenticating transactions. In particular, finding small hashes is completely useless for the world. Are there ...
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1answer
54 views

1-CPU-1 Vote Bitcoin confusion

How does the 1-CPU-1 vote works because if we're talking about miners doing computation power to vote, then successful solver of the hash wins the block, so basically only the single cpu (considering ...
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2answers
165 views

Would an optimization proof-of-work problem where the entity with the lowest hash wins have any security weakness or other disadvantage?

I am wondering if there would be any security deficiencies if cryptocurrencies such as Bitcoin were to change their proof-of-work problems to optimization contests. For example, suppose Bitcoin were ...
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57 views

Is a proof of work consensus mechanism that discourages mining in pools possible?

Most proof of work cryptocurrencies, including Bitcoin, have most of their hashrate controlled by the biggest mining pools which significantly decreases decentralization. Would it be theoretically ...
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2answers
104 views

Decreasing Energy Consumption of Bitcoin's PoW with paired mining rounds

I found the following whitepaper on an algorithm called "Green-PoW" by the authors and i'm quite sure this would be a perfacet solution and also would get acceptance by the miners and the ...
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6answers
23k views

Why doesn't Bitcoin migrate to proof-of-stake?

After reading a little bit about different consensus algorithms, I am just trying to understand why Bitcoin still uses proof-of-work. This consensus algorithm being exponentially expensive, and ...
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1answer
791 views

Block Hash and Nonce generated by GenesisH0 python script is incorrect

After running GenesisH0 python script to generate the Genesis block for a local testnet (using v0.15.1), I got the following results. merkle hash: ...
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25 views

Can Scrypt be reduced to SHA256 proof of work?

Interested because if a reducer exists then Bitcoin mining pools would be able to use a fraction of their hash power to assert dominance on altcoins by regularly deploying 51% attacks on the altcoins ...
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2answers
669 views

Could BTC be changed so that it limited the amount of computation power a given miner used?

I am assuming this would be hard or impossible to prevent miners from circumventing but would there be a way to change the algorithm to limit how many transactions a given mining installation could ...
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1answer
46 views

When should proof-of-work be done? Does it involve in mining a coin? Can it be done without real transactions to be recorded?

I am trying to understand about what bitcoin is. I conceptualize bitcoin as a proof of work required when a new block (or new coin) is created. I also understand that a proof of work involves finding ...
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1answer
218 views

How does bitcoin implement checkpoint mechanism to finalize the blockchain history?

I read in Peercoin whitepaper that to prevent large blockchain reorganization, bitcoin also implements checkpoint mechanism which finalizes the blockchain history. Can you explain how exactly bitcoin ...
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1answer
107 views

51% attack, miners, nodes or both

If 51% of the hashrate was controlled by bad actors mining invalid blocks, this would become the longest chain. Where do nodes come into the 51% attack? The canonical chain is the longest chain. Is ...
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1answer
45 views

How are txns sorted correctly in Merkle trees between nodes and validated via Proof of Work

I am interested in exactly what happens to transactions in the pending block (block that is being mined at the time). From what I understand, transactions are the stored as a Merkle tree hash inside ...
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4answers
1k views

What is the problem that mining solves?

Of course, the function of mining is to secure the blockchain, but I'm looking for a more abstract summary of what the exact problem is that mining tries to solve? I believe its called the Byzantine ...
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18 views

Why the mining process is necessary? [duplicate]

I understand that the main purpose of the mining process is to maintain the network and protect it from fraud. However, every transaction is signed by the sender's private key, and then it's verified ...
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9answers
2k views

How does a blockchain relying on PoW verify that a hash is computed using an algorithm and not made up by a human?

How does a blockchain verify that the hash provided (the one with the leading zeros that is supposed to be unique, computed using lots of processing power) is indeed unique and that it wasn't just a ...
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1answer
23 views

How is “cumulative PoW” calculated to decide between competing chains?

Chain 1 has blocks with targets diff1, diff2, diff3, diff4 Chain 2 has blocks with targets DIFF1 DIFF2 DIFF3 What's the formula to derive the (relative) cumulative proof of works from these chains to ...
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79 views

Why aren't public-private keys sufficient to build a block chain? Why do we need proof of work/stake?

Taking the simple case of Bitcoin here: If all nodes can validate published transactions by checking the signature (created using the private key of the sender) of the transaction against the public ...
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1answer
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Confused about POW

I'm pretty new to crypto and I'm confused about POW POW Is usually explained like this... A group of transactions are bundled into a memory pool (mempool). Miners verify each transaction in the ...
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2answers
111 views

Why proof of work rather than posting to a public forum?

I understand that proof-of-work plus a block chain is one way of creating a trustworthy public ledger of transactions. But holy hell, the cost to society in terms of energy consumption is VERY high ...
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2k 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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1answer
82 views

Proof of Work vs. Proof of History

Can someone explain the context of what Nakamoto exactly meant with: "To implement a distributed timestamp server on a peer-to-peer basis, we will need to use a proof- of-work system..."? I ...
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1answer
42 views

terminology and conceptual question about progress of PoW

what is wrong about thinking prbobability of attacker increases with time t that goes into PoW since they have more time to secretly mine their alternate blockchain ? This refer to double ...
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433 views

Is verification of a blockchain computationally cheaper than recreating it?

One of the advantages of cryptocurrencies like Bitcoin that is often repeated is how hard it should be to manipulate past transactions. The reason that is often stated is that you would have to re-...
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67 views

Can there be Bitcoin-like network that also works as whatever@home? [duplicate]

There are Bitcoin-like network that performs calculations that are not locally useful, but interesting for peers. There are {SETI,folding,...}@home networks that calculates something that is (...
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88 views

Can we measure bitcoin's accumulated work in terms of entropy (in bits) directly rather than expected number of hashes?

The Background Bitcoin tracks chain work by counting the (expected) minimum number of hashes it would take to create a chain of the same number of blocks and same difficulty steps[1]. Naturally, ...
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1answer
48 views

How to calculate economic security for bitcoin proof of work?

Is this the correct way to calculate security for bitcoin proof of work? https://twitter.com/drakefjustin/status/1356918733441294336 If a government or group of few rich people or organizations create ...
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5answers
747 views

After sending/flooding transactions, how do we know that a specific transaction is on all nodes?

In the book "Mastering the Blockchain" by Imran Bashir, it says that a transaction's life cycle is the following: A user/sender sends a transaction using wallet software or some other interface. ...
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3answers
780 views

Why does the “global lottery” prove the validity of the blockchain?

As far as I understand it currently, when winning the "lottery" (mining) you can add a block, sum of transactions, to the blockchain. This block is in the first instance verified by all network users. ...
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3answers
857 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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4answers
968 views

Is mining the unfair part of bitcoin in the same way banks (or rather, fractionary reserve systems) are to current monetary system?

I've been reading a lot about bitcoin lately and I'm very interested. Especially, when it comes to making a currency that is way more fair, because it avoids a centralized control of it. However, in ...
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22 views

In a closed, working test network, how would I generate a signed block that a Bitcoin miner would otherwise create?

I have a POC where the essential, critical, priority goal is to use C# and the .NET Core Framework (Bouncy Castle for crypto, or Microsoft primitives for BigInteger ) where I do the following Accept ...
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1answer
426 views

Chain with most proof of work - hash target or block header hash?

What is calculated towards the sum of PoW of the chain? Is it the target difficulty that has been met or is it the actual block header hash? Say the target is 000000ABC00000000... and I mine block ...
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1answer
290 views

Difference between PoW and BFT

What is the difference PoW algorithms (as used in Bitcoind) and BFT (used for instance in Libra) ?
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60 views

Are Bitcoin transaction fees competitive?

I was listening today to their conversation about the transcation fees in Bitcoin and Michael Sailor's understanding stroke me as inaccurate. Is there any direct incentive within the Bitcoin protocol ...
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1answer
47 views

How a transaction is permanently accepted by the blockchain?

If a miner A creates a block containing a transaction A and a miner B creates a block NOT containing the transaction A about at the same time, then some of the other miners will first receive the ...
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2answers
74 views

What exactly makes altering of data in non-bitcoin blocks hard?

If leading zeros is only bitcoin requirement, then what makes altering of data in blocks hard? Like now its easy to modify a block and generate new hash for every subsequent blocks since generating ...
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1answer
40 views

How many numbers to try to solve the proof-of-work problem

I'm preparing for a lecture on blockchain, where I'm going to briefly explain the proof-of-work mechanism and the hashcash challenge. To illustrate the difficulty, I want to give the maximum amount of ...
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1answer
155 views

how and when does block and transaction validations take place?

I have a couple of questions and will try to explain them here. So, let's say we have 4 nodes in the whole network. one of the nodes (node A) took transactions from pool. before they put it into a ...
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20 views

How do bitcoin verifies block hash after new hash have been submitted by Miners? [duplicate]

I want to know how at the end of Bitcoin server block hashes are verified after it has been submitted by a miner. Do they already have a previously calculated block hash DB or something else? I m new ...
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1answer
275 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
61 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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2answers
401 views

Do multi-PoW currencies open up additional attack vectors on a blockchain?

I'm curious if there have been any technical evaluations of the vulnerabilities of cryptocurrencies that utilize more than one proof of work algorithm - for instance, myriadcoin or huntercoin. ...

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