# 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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### Probability of mining maximum of 3 block in next 20 minute

I know that block interval in bitcoin blockchain is exponential distribution. Now I want to know what is the probability that maximum of 3 block will be mined in the next 20 minute?
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### Is there a consensus as to what is meant by 'Nakamoto Consensus'?

I sometimes hear that bitcoin's key innovation was the Nakamoto Consensus, which solves the double-spend problem without the need for trusted third-party intermediaries. I take Nakamoto Consensus to ...
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### Is it correct to refer to hashes found through proof of work as "proof of work numbers"?

I've seen come commentators refer to 'proof of work numbers'. I suppose these are the hashes found through proof of work, but not entirely sure. EDIT** Regarding where I got the 'proof of work numbers'...
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### What stage of the bitcoin protocol deals (or 'solves') the double-spend problem?

I understand that a key innovation in bitcoin is that it solves a key problem faced by previous attempts at a digital currency: the double-spend problem. In addition, I also understand that the ...
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1 vote
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### Proof that blockchain converges to the longest chain [duplicate]

Is there a mathematical proof that shows that blockchain converges to the longest chain? It seems not obvious to me how a scattered group of nodes and transaction signals will eventually converge to a ...
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### Is it correct to differentiate between a validated bitcoin transaction and a confirmed bitcoin transaction?

From my understanding, a transaction is first 'validated' by nodes once a transaction is propagated - so in the early stages. These validated, but unconfirmed, transactions are then collected by ...
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### Mining against candidate block hash or previous block hash? [duplicate]

When mining...; a) Is the block header hash of the candidate block used b) OR the block header hash of the previous block + noonce used? If it is a), which I presume, is it then correct that the ...
• 1
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### Can you get the longest chain by keeping a constant low difficulty?

I'm struggling with this question that should be easy to answer. If the truth is the longest chain, what if I redo all the work from Block 1 until I have the longest chain by keeping a constant low ...
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1 vote
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### How does PoW ensure that all the transactions are recorded and that all the transactions are valid?

I just started to study blockchain and bitcoin yesterday and came up with some questions. If miners can select transactions when creating a block, how is it ensured that all the transactions over ...
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### Can a proof of work chain have finality?

My understanding is that finality is just a rule in the consensus which says any block that gets buried X block deep will be considered unchangeable by the consensus. This has nothing to do with proof ...
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### Why is PoW even necessary?

So I understand the concept behind PoW (that if someone wants to overturn the current chain, they'd have to do all that work again). But why is it even necessary since transactions are confirmed only ...
1 vote
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### Will we have blocks with hash 000...000 (all zeros) in the year ~2070 if hashrate will increase with the same rate?

I have made an estimate on when the total hash rate will be high enough that we might observe blocks that have a hash with complete zeros. ...
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### Could one create an offline full node network mining node?

I'm curious if Bitcoin is vulnerable to this: Create thousands of virtual machines, all "networked together". Download the current full Blockchain and register each virtual machine as a ...
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### When transactions of orphan block go back to the mempool?

Imagine there are two collision blocks A and B. These are mined at the same time. One miner created new block C on top of block A and longest chain happened. Do transactions of block B go back to ...
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### When one miner created a new block and won the mining race, what other miner do next?

Imagine that wee have 10 indexed blockchain. Now, I start mining for index 11 block referencing index10's hash, I mean, the last hash data. Also, other miners starts too. When other miner finishes ...
1 vote
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### If malicious person(node) tampered withone block transaction, what's gonna happen?

I understand that if one bad person(node) tampered one block of his/her blockchain, the block hash data changed completely different. Let's say each node has 10 indexed blockchain and index4 block has ...
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### how do nodes agree or disagree after new block is create?

I'm new to blockchain field and I read one article. article In this article of Authorization chapter, it is said that "For a public blockchain, the decision to add a transaction to the chain is ...
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### Can we benefit from Collatz conjecture-based proof of work?

Can we benefit from Collatz conjecture proof of work to enhance bitcoin utility? F Bocart 2018:"Inflation Propensity of Collatz Orbits: A New Proof-of-Work for Blockchain Application" argues ...
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### Changing the blockchain requires more than just recalculating all hashes..?

New here! I read this everywhere - "To change some data in a blockchain, the malicious user will have to recalculate hash for every block starting from that particular block". My doubt is - ...
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### Why the Proof of Work solve the double spending problem?

I'm learning about blockchain and I somehow struggled to understand why the POF is the solution of double spending in bitcoin. From my understanding, the POF is the method to create new block, which ...
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### Determination of Block Size Limit

In Bitcoin Mining, there is a limit on the size of any block added to the chain. What happens if, for instance, a block's nonce is so large that the block's size exceeds the limit? Secondary questions:...
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### Does Proof Of Stake have any intrinsic scalability Advantage over Proof Of Work?

Is there any intrinsic scalability advantage to using proof of stake over proof of work? Ignoring the environmental impact issue, and ignoring sidechains, can proof of stake achieve higher TPS rates ...
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### Would Bitcoin still work without a target difficulty?

Suppose that Bitcoin nodes had no target difficulty at all, and instead just accepted the block with the largest PoW every 10 minutes. Ignoring the increased bandwidth (since nodes would be ...
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### How to get unconfirmed transactions

I am trying to learn how mining is done in bitcoin , wrote a simple mining code in python that works fine on sample data set of raw json coming from https://btc.cryptoid.info/btc/block.dws?693649.htm, ...
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### How often does the "little man" win [mining]

I have read that long term we expect that the percentage of blocks mined to be forever converging to the percentage of hashpower possessed by the miner. This means if a particular miner has 20% of the ...
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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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 ...
1 vote
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### 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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### 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 ...
1 vote
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### 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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### 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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### 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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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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### 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 ...
1 vote
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### 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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### Why is Bitcoin not moving to an ASIC-resistant Proof of Work algorithm?

Bitcoin uses a Proof of Work algorithm that makes it the perfect victim of ASIC mining. As a result, hash power is not very decentralized (more than 50% of Bitcoin's hash power is concentrated in ...
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### 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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### 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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### 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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