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
240 views

In Proof-of-Stake, can a block creator fudge the block hash?

In Proof-of-Work, a block hash is costly to manipulate (say, wanting the hash to be even, or have the hash of the hash smaller than some number) since there is a lot of computing power put into ...
3
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1answer
939 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 ...
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3answers
569 views

Is there a proof of work system which takes significantly more memory to generate than it does to verify?

Litecoin resists GPU speedup by using an scrypt-based hashing function that takes some amount of memory to generate and verify. The problem with this is that the r parameter needs to be set high ...
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1answer
1k 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" ...
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2answers
10k views

Bitcoin alternative designed for NVIDIA

Currently the best graphics cards to mine Bitcoins are all AMDs. What should be changed in the Bitcoin protocol to make the alternative version of Bitcoins better mined by NVIDIA graphics cards? Could ...
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5answers
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 ...
4
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1answer
536 views

What is proofOfWorkLimit?

Look at the code below from android bitcoin wallet: proofOfWorkLimit = Utils.decodeCompactBits(0x1d00ffffL); And look at the code from bitcoin qt wallet: static CBigNum bnProofOfWorkLimit(~uint256(...
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1answer
496 views

Abrupt increase in difficulty of proof-of-work

I am simulating a private bitcoin network that I started with the initial difficulty set to (1/2)^16, however after about 20 blocks of mining on the network it increased to 1 and has been constant ...
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2answers
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 ...
2
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1answer
409 views

Where is the spec of HashCash so that I can implement it in Java from scratch?

I would like to implement HashCash in an efficient/fast/garbage-free way. Is there a spec to do so? How can someone go by implementing HashCash from scratch?
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1answer
122 views

What are the chances of someone coming up with a new and simple/out-of-the-box solution for the double-spending problem?

The proof-of-work solution is simple but has many drawbacks (waste of time, energy and uncertainties about its security in the future). The consensus solutions proposed by Ripple/Stellar are too ...
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2answers
634 views

What is the hash function used by Bitcoin proof-of-work?

Probably a simple question, but I believe it is important to state it clearly for the beginners like me out there. What is the hash function used for the Bitcoin proof-of-work? What implementations ...
2
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1answer
443 views

Challenge difficulty adjustments

Basically for this question I need a confirmation that all of my listed assumptions are fairly accurate. The bitcoin network measures how much time it took to create the last 2016 blocks in a ...
4
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2answers
385 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 ...
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1answer
717 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 ...
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2answers
2k views

Generating blocks in regtest: “hash doesn't match nBits”

I'm getting this error in regtest mode after setgenerate RPC: ERROR: CheckProofOfWork() : hash doesn't match nBits After looking for error text in src I found a match in pow.cpp (obviously ...
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1answer
259 views

Sample proof of work in Ruby, what am I doing wrong?

Given the following block, how do I verify the proof of work? I got this data from bitcoin-cli getblock and parsed in to a Ruby hash called data: {"hash"=>"...
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2answers
156 views

Are there any stochastically dependent proof of work algorithms?

In bitcoin, the probability of discovering a block on the X-th hash is the same1 as it is on the Y-th hash. As such, the probability of discovery is stochastically independent. Are there proof of ...
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2answers
82 views

Theoretical security of mining bitcoins

Is it possible to change rules of mining bitcoin division? rewrite P2P bitcoin client (or write maleware) which will be pretending that fake bitcoin client is legal, original client distribute ...
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2answers
374 views

What is the reason for using PoW in bitcoin?

As we know bitcoin uses Proof of Work Concept and it introduces never ending long block chain and some other issues. Why is it not designed in a way to use consensus algorithms what ripple uses? What ...
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3answers
1k views

Difference (if any) between proof-of-work in mining bitcoin vs verifying transaction

I'm trying to understand the proof-of-work idea for verifying a transaction. I think I understand why proof of work is needed to verify transactions (essentially to prevent spoofing/double spending ...
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1answer
1k views

Confirmation limit

When seeing transactions I see that the number of confirmations keeps increasing without any limit. I wanted to know if there is any time limit on including a already confirmed transaction in a block ...
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3answers
515 views

Can the Bitcoin blockchain eliminate the need for Trusted Computing in Smart Contracts?

Let me preface this by saying that I'm a novice, but this is my rough understanding of how Bitcoin's blockchain works. (This is largely based on blog posts like this one.) If person A wants to ...
3
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1answer
238 views

Why do some mining algorithms run “cooler” than others?

So, there are some altcoin mining algorithms now that run cool, such as X11 and groestl. By cool, I mean even when mining at full GPU capacity, the card still remains at 60C or cooler with little to ...
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1answer
175 views

Bitcoin related research areas [closed]

I have a one year research project in my MSc curriculum. So i was suppose to address a existing issue in bitcoin protocol. Highly appreciate if someone can advise me and give me some ideas. Thank you....
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2answers
308 views

What is the variable in a block that holds hash of found PoW?

Can anyone please tell me, which variable holds the hash of the solution of block's PoW in broadcasted block? I know that a block consists of (I am pretty sure I am forgetting some variables here): ...
4
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2answers
791 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 ...
3
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2answers
3k views

How transactions get added to a ledger?

I just can't seem to understand how bitcoin works. Here is what I understand so far. Alice sends 1 Bitcoin to bob's public address A new transaction gets created for miners to approve. A transaction ...
4
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1answer
4k views

Work rejected. Server says: Stale or alien proof of work

I get this error using BitMinter Client v1.3.2: Work rejected. Server says: Stale or alien proof of work about every 15 - 45 minutes, just mining on my GPU. What is happening? What does it mean to ...
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2answers
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 ...

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