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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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.
Phonics The Hedgehog's user avatar
113 votes
13 answers
13k 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 ...
Artem Kaznatcheev's user avatar
163 votes
6 answers
290k views

What are bitcoin miners really solving?

As with mining, what are the bitcoin miners really solving? I read they are solving hashes, but what does that really mean. Can we see what they are solving? Can someone give an example of what a ...
Patoshi パトシ's user avatar
16 votes
2 answers
2k views

How can we be sure that a new block will be found?

How do we know the HASH function will produce an output that fulfills the difficulty, i.e. is below 0000...xxxx...xxx? Is it possible that no proof will be found so that the HASH will produce that ...
user4691's user avatar
  • 261
11 votes
4 answers
3k 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 ...
mrwnt10's user avatar
  • 213
10 votes
2 answers
4k views

Will the proof-of-work system end when all bitcoins have been mined?

This article from ArsTechnica is claiming that Bitcoin is not such an environmental disaster, and one of the reasons they mention is that mining will come to an end. Ok, fair enough, there is an end ...
knocte's user avatar
  • 1,754
20 votes
6 answers
10k views

Why do we need Proof of Work in bitcoin?

I know that proof of work shows that the person has put in some time and power into the processing. I also know that bitcoin mining is adding a transaction into the blockchain and then the miner will ...
user153882's user avatar
19 votes
3 answers
12k views

What is proof-of-work?

Please explain the proof-of-work concept. And how does it relate to Bitcoin mining in general, and to the proofs of work (aka shares) of mining pools?
Dr.Haribo's user avatar
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44 votes
6 answers
30k 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 ...
Oscar Serna's user avatar
28 votes
1 answer
12k views

What is proof-of-stake?

As we know one of the important mechanisms of Bitcoin is proof-of-work. How does the concept of proof-of-stake work? How does it differ from proof-of-work?
Dr.Haribo's user avatar
  • 8,429
12 votes
2 answers
850 views

Is it possible for the network to stop finding valid blocks?

The hashing problem is by design computationally hard, because SHA-256 hashes are for all intents and purposes random strings with no direct link to their inputs, and there's no (known) way to ...
Massimo's user avatar
  • 1,058
7 votes
2 answers
2k views

How is it that concurrent miners do not subvert each other's work?

Every time a new block is added on top of block chain, the miners have to restart their work because the next block has to have a proper reference to previous block. Let's suppose that there is some ...
czerny's user avatar
  • 247
31 votes
3 answers
45k views

How does proof-of-stake "mining" work? [closed]

I know and understand the concept of proof-of-stake. Instead of requiring users to do a certain amount of power-intensive hashing "work", it requires you to own a certain stake of the currency in ...
Steven Roose's user avatar
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4 votes
3 answers
393 views

Egoistic miners combined with large transactions destroy PoW?

EDIT There is a clearer description of some parts of the problem in the link questions. If there is a transaction value much higher than the payment for mining 10 new blocks, how can you trust this ...
user avatar
6 votes
2 answers
2k views

What happens to extinct blockchains, and transactions inside of them?

While understanding the concept of block chain and proof of work, few things are confusing me. Miners always consider the longest chain(by difficulty) and work on expanding it. Now, lets say two ...
Avikarsha Mandal's user avatar
2 votes
3 answers
6k views

How proof of work prevents double spend

One article I am reading said that proof of work system is used in Bitcoin to prevent double spending. More particularly: Imagine we are protecting against double spending in following way. When Bob ...
user avatar
26 votes
3 answers
82k views

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 ...
Mark Ma's user avatar
  • 395
23 votes
2 answers
5k views

What are the pros and cons of Ripple's consensus as compared with Bitcoin's proof-of-work?

One of the major differences between Bitcoin and Ripple is how they process transactions. I can think of three ways in which Ripple's "consensus" scheme is superior to Bitcoin's proof-of-work: Less ...
Manish's user avatar
  • 2,022
18 votes
3 answers
5k views

Are there alternatives for proof of work?

Bitcoin uses proof of work to secure the network, Ripple uses a global consensus system and PPCoin uses proof of stake. Are there any known alternatives to the above methods?
Maestro's user avatar
  • 1,967
12 votes
2 answers
2k views

Bitcoin without mining

Several months ago I've stumbled an interesting question about the Ripple system: How does Ripple solve the double-spend problem? Specifically about how double-spending is solved in Ripple. As you ...
Luca Matteis's user avatar
  • 5,202
8 votes
3 answers
6k views

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 ...
R V's user avatar
  • 83
7 votes
4 answers
2k 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,...
hellopeach's user avatar
4 votes
1 answer
2k views

How does a time warp attack work?

I more or less understand how an attacker (with less than 50%+1 of the hashing power) can artificially lower the block difficulty by messing with timestamps. I also understand how such an attacker ...
Cedric Martin's user avatar
3 votes
3 answers
1k views

Why you need to rehash each block after a changed block when changing data in a blockchain?

Maybe my question is stupid, but, why you need to rehash each block after a changed block when changing data in a blockchain? Each block contains a hash of its data and hash of previous block. If I ...
umaru's user avatar
  • 33
3 votes
1 answer
1k views

Difference between PoW and BFT

What is the difference PoW algorithms (as used in Bitcoind) and BFT (used for instance in Libra) ?
vincenzopalazzo's user avatar
1 vote
1 answer
1k views

How does the bitcoin transaction fee get paid to miner(s)?

According to https://bitcoinfees.info/ The current "cheap" rate for a bitcoin transaction is $22. How does this get paid to the miners? Is it just one miner that verifies the transaction, puts it ...
nanonerd's user avatar
  • 137
1 vote
1 answer
746 views

Why is POW/POS absolutely necessary to run public distributed ledger?

my first question here, so please be patient with me. Thank you in advance. Q: Why exactly are POW/POS mechanisms needed to secure the blockchain (in bitcoin as well as in other alts)? + what is ...
igni's user avatar
  • 11
1 vote
1 answer
327 views

A theoretical low cost attack scenario in PoW currencies

The scenario was designed by user:croraf and me in discussing a question of mine yesterday. To make it more clear, I want to present it here again in a stricter design. To do it in a clear way, first ...
user avatar
13 votes
4 answers
9k views

Why can't we design a bitcoin that does useful work? [duplicate]

The bitcoin network, including every miner, is the biggest computing project that humanity has created. Thus I ask: why, instead of using it to generate useless data, don't we use it to generate ...
Dokkat's user avatar
  • 139
13 votes
2 answers
3k views

What is Proof of Burn?

Can someone explain me: What is Proof of Burn What is the difference between Proof of Burn and Proof of Work How Proof of burn works Which virtual currency uses Proof of burn technology instead of ...
tdumidu's user avatar
  • 379
10 votes
5 answers
7k views

What features of scrypt() make Tenebrix GPU-resistant?

There's a fork of Bitcoin called Tenebrix that is claiming to be CPU-friendly and GPU-resistant (with regard to mining). They say that this is because they're using scrypt instead of SHA256. From what ...
David Perry's user avatar
  • 14.4k
10 votes
4 answers
1k views

Is it possible to make PoW ASIC-resistant through dynamically generated hash chains?

Bitcoin's static proof-of-work function SHA256(SHA256(data)) was apparently easy enough to be implement as ASIC which lead to the re-centralization we see today. But what if the PoW function changes ...
ToBe's user avatar
  • 133
9 votes
3 answers
5k views

Probablity Distribution of mining

What is the probability distribution of solving a block, given the same difficulty. So if I try to mine multiple times using the same difficulty, is it normal distribution with mean of 10 minutes? ...
jaybny's user avatar
  • 173
9 votes
3 answers
6k views

How does Proof of Burn work?

I have been trying to make a comparison between PoW, PoS and Proof of Burn. While I understood the other two, I want to know how exactly Proof of Burn helps in attaining the consensus. One burns ...
trollster's user avatar
  • 260
9 votes
1 answer
1k views

What prevents similar time-warp attacks in Bitcoin as happened to Verge?

Right now (may 2018), Verge (an altcoin with proof of work) was attacked by time-warp attack. More can be read here https://blog.theabacus.io/the-verge-hack-explained-7942f63a3017 What exactly ...
Karel Bílek's user avatar
  • 2,685
6 votes
4 answers
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 ...
Maestro's user avatar
  • 1,967
6 votes
2 answers
1k views

51% attack and rewriting to the latest checkpoint

This is not a question about the consequence of a 51% on the price nor as to the motivation of the attacker. Let say we don't care that it's not realistic and we don't care that the attacker wouldn't ...
Cedric Martin's user avatar
6 votes
3 answers
2k views

Does every nonce really have an equal chance of winning?

I set out to test the claim: "Every nonce has an equal chance of winning." Time Evolution So, I plotted, with gnuplot, the nonce values vs. hashes for all the valid blocks in the blockchain:(Also, ...
Geremia's user avatar
  • 4,606
5 votes
1 answer
771 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 ...
Questioner's user avatar
  • 1,151
4 votes
1 answer
591 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 ...
Gerard Bosch's user avatar
4 votes
2 answers
884 views

Could an algorithm be made ASIC-resistant by simply adding deterministic permutations depending on the hash of the previous block and the nonce?

I was thinking of permuting bits in a block before it is hashed, in order to require some adaptability from the mining hardware while retaining the security of SHA-256. Permutations would depend on ...
arkanaprotego's user avatar
4 votes
2 answers
447 views

Is there a PoW system that shows cumulative work without an ever-increasing proof size?

Let's say I have an output in the blockchain at height 100,000. At height 200,000, I want to prove that my output has the work of 100k blocks built onto it, securing it. In Bitcoin, proving that the ...
morsecoder's user avatar
  • 14.1k
4 votes
4 answers
8k views

If SHA256 produces an alphanumeric hash, how can a hash be "less than a certain value"?

I was under the impression that Bitcoin's method for validating a hash involved making sure the hash started with a pre-determined number of zeroes. However, after reading the docs here, I see the ...
Richie Thomas's user avatar
3 votes
1 answer
1k views

Why change the nonce instead of just rehashing?

Why do miners increase the nonce to compute a block hash rather than just generating a random block hash? It seems to me that both approaches would have the same likeliness of finding a result that ...
Glenn's user avatar
  • 133
2 votes
1 answer
123 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?
monkeyUser's user avatar
2 votes
2 answers
1k views

How can a block be considered more difficult to solve/hash than another one?

In this answer: https://bitcoin.stackexchange.com/a/760/28219 It is said: Because of all this work, when a Bitcoin client signs on to the network it can trust the block chain that was most ...
Peter Mel's user avatar
  • 625
2 votes
1 answer
317 views

Can the mining pool with the most mining power always win? [duplicate]

Suppose we have three mining pools, one with 40% of computing power, and the other two having 30% of computing power each. Will the node with 40% power, be able to solve the puzzle for each node ...
George Tsichritzis's user avatar
2 votes
1 answer
2k views

What sort of calculations do the miners have your computer do? [duplicate]

I recently heard of a new cryptocurrency (or maybe it's not new and I'm just out of the loop) called Gridcoin which uses your GPU/CPU/ASIC to do research calculations rather than "meaningless" ...
Fuzail Gilani's user avatar
2 votes
1 answer
491 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 ...
Wapac's user avatar
  • 1,064
1 vote
1 answer
240 views

Creating blocks while more transactions arrive and proof of work mechanics

I am having a hard time understanding the details of how blocks are getting created by miners while many transactions are being received by various nodes at slightly different times and what ...
verkter's user avatar
  • 113