Questions tagged [difficulty]

This tag should be used for questions regarding difficulty which encodes the likelihood of one hash to succeed at mining a block. Indirectly, it is a measure of the total hashing power of all miners for a given cryptocurrency.

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78 votes
3 answers
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How is difficulty calculated?

Can anyone explain me in the plain English how difficulty is calculated. I have a very approximate understanding that it is calculated based on the amount of hash power in all the bitcoin community ...
Salvador Dali's user avatar
60 votes
4 answers
33k views

What keeps the average block time at 10 minutes?

I've been told "the network" sets the difficulty level such that there will be one new block mined every ten minutes. I imagine the rich would instead prefer to keep difficulty as high as possible to ...
billpg's user avatar
  • 2,030
42 votes
8 answers
21k views

Can bitcoin exist without miners?

In the past year only, the bitcoin mining difficulty has increased fivefold. If in the coming years the difficulty increases so much that mining is no longer profitable (i.e. consumes more power than ...
Eduard Avetisyan's user avatar
32 votes
6 answers
123k views

Do these new ASIC miners really pay for themselves in 5 days?

The Bitforce 50GH/s miner costs $2,500 today, and according to the following calculation it would mine enough coins in about 5 days to pay for itself. I am sure I am missing something here. Why would ...
Simon's user avatar
  • 423
28 votes
3 answers
17k views

What is "difficulty" and how it relates to "target"?

I don't understand what "difficulty" means and how it really relates to "target". I understand what "target" is - it tells the miners, how small the resulting hash should be. (Basically, how many ...
Karel Bílek's user avatar
  • 2,685
24 votes
2 answers
16k views

Relationship between Hash-Rate and Difficulty

What is the algebraic relationship between Total Network Hash-Rate and Difficulty?
Kinnard Hockenhull's user avatar
22 votes
1 answer
14k views

How does the Kimoto Gravity Well regulate difficulty?

Maxcoin will use the Kimoto Gravity Well (KGW) to regulate the difficulty. From what I could find about the KGW, it retargets after every block and adjusts very quickly, e.g. when multipools add and ...
Murch's user avatar
  • 74.4k
21 votes
3 answers
66k views

What does the mining difficulty number really mean?

I'm new to bitcoin; please bear with me. I'm looking into mining, how it works, and how to get started. I see a "mining difficulty" from many sources and list a 3 billion something number without ...
user avatar
18 votes
6 answers
35k views

Why can't they use super computers to mine all the bitcoins?

I have very limited knowledge of bitcoin, but, I hope you don't mind my asking this question: As I understand it, "mining bitcoin" requires "significant" computational prowess. A lot of dedicated ...
thatmaheshrs's user avatar
18 votes
4 answers
43k views

Can casual people still mine for bitcoins, now that the difficulty is much higher than it was?

Can casual people still mine for bitcoins? As of October 2012, the difficulty seems very high, being over 3,000,000. I've seen a ad for bitcoins, and watched the video. It said I could mine for them ...
Rook Ward's user avatar
  • 181
17 votes
3 answers
8k views

How to calculate new "bits" value?

Every 2016 blocks one needs to calculate new bits value. What is the formula to calculate it?
ThePiachu's user avatar
  • 43.1k
16 votes
2 answers
4k views

What happens if hash rate decreases rapidly?

Since difficulty is only adjusted every 2016 blocks, what would happen if hash rate was to decrease rapidly? Wouldn't this cause blocks to be created less frequently and also making the time until ...
D.H.'s user avatar
  • 5,307
15 votes
2 answers
2k views

How many Integer Operations on a GPU are necessary for one Hash?

I thought it was the ALU OPs like here: https://bitcointalk.org/index.php?topic=7964.0 ArtForz speaks of much higher values, though: https://bitcointalk.org/index.php?topic=4689.msg68933#msg68933 ...
kermit's user avatar
  • 2,019
13 votes
3 answers
13k views

What are the equations to convert between bits and difficulty?

If we take block hash 0000000000000006770c3806960539ca83a24facbd99ea212f37f2a0e6a5629a for example. The difficulty as a 32 bit float is 50810339.04827648. The difficulty in bits as an unsigned 32 bit ...
Dan's user avatar
  • 419
13 votes
4 answers
4k views

Is there empirical data about a relationship between bitcoin price and difficulty?

There have been claims that Bitcoin price and difficulty correspond. Is there empirical data to support or refute this?
ripper234's user avatar
  • 26.6k
12 votes
2 answers
848 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
11 votes
2 answers
295 views

Why are block header bits necessary? (Valid difficulty is already implied by chain history)

Difficulty or target is implied by chain history, so why does it need to be explicit in the header? I suppose it exposes miner-intended-difficulty, but I don't see why that would be relevant without ...
James C.'s user avatar
  • 2,511
10 votes
2 answers
2k views

Is there a maximum factor by which difficulty can change?

I seem to recall, long ago, being told that difficulty couldn't change more than a certain amount at each retarget, but I can't seem to find what that factor is (or even confirmation that such a ...
David Perry's user avatar
  • 14.3k
10 votes
4 answers
873 views

What is the ecological effect of increased work for the Bitcoin chain?

As more users use Bitcoin and "forced work" difficulty increases what effect does this have ecologically? It is a silly question I know. I'm just comparing let's say value or effect of using ...
cyphunk's user avatar
  • 201
9 votes
3 answers
9k views

How is the target section of a block header calculated?

I've been poking around https://en.bitcoin.it/wiki/Target and I've found the current target, but I can't seem to find how it's generated. It's supposedly generated when the difficulty is adjusted, as ...
Dylan Katz's user avatar
9 votes
8 answers
3k views

Can more than 1 block be solved per 10 mins on average (LONG TERM)?

I am wondering whether it is possible for a supercomputer to find the next 1000 blocks in a very short amount of time. Hypothetically, if a government agency concentrated a supercomputer on hashing, ...
R--'s user avatar
  • 91
9 votes
2 answers
19k views

How many zeroes does the current target have? [duplicate]

I'm trying to get my head around the difficulty setting of Bitcoin. How can I calculate how many zeros the target string needs to start with?
Alice's user avatar
  • 91
9 votes
4 answers
2k views

Why invest in mining hardware if the difficulty continues to climb at an exponential rate?

From the FAQ : Creating a block is a proof of work with a difficulty that varies with the overall strength of the network. So with these purty graphs there is a continuous exponential trend in ...
Chris O's user avatar
  • 191
9 votes
1 answer
1k views

Reduce difficulty on testnet-in-a-box?

I'm doing some testing and often find myself needing to generate 6 blocks quickly to confirm some tx. Each block takes a few minutes to generate on my macbook so this slows things down considerably. ...
Brian Armstrong's user avatar
8 votes
2 answers
2k views

Why is it harder to compute nonce for a hash with a certain number zero prefixes than it is for any other hash?

Based on my rudimentary understanding of Bitcoins and altcoins, network difficulty is adjusted by asking the network to target a hash smaller than a specific number, which translates to calculating ...
CodeMangler's user avatar
8 votes
3 answers
758 views

Why this ugly looking formula to calculate 'target' from 'nBits' in block header: target = coefficient * 256**(exponent-3)

Why this ugly looking formula to calculate 'target' from 'nBits' in block header: target = coefficient * 256**(exponent-3). Why not? : target = coefficient * 256**(exponent). What is the need of ...
Ravi Patel's user avatar
8 votes
4 answers
2k views

Why was it chosen to adjust difficulty every 2 weeks (rather than 2 days or every few blocks)?

Is there a benefit to adjusting the difficulty every so often (ie 2 weeks) vs adjusting the difficulty every block?
B T's user avatar
  • 1,638
8 votes
1 answer
313 views

Why is target stored in the block at all?

Currently, target is stored in each block. Why is that? Why it is not simply computed by each client based on the previous timestamps from previous blocks? Why it has to be stored within the block? ...
Mitar's user avatar
  • 183
8 votes
5 answers
9k views

Will expensive mining equipement have any worth in the future?

With more and more people picking up advanced ASIC miners, the difficulty is going up while the remaining coins are going down. If miners continue joining at this or a faster rate, the limit might be ...
ZCoder's user avatar
  • 325
8 votes
2 answers
14k views

Calculating average number of hashes tried before hitting a valid block

I'm toying with the idea of starting to mine, and was wondering how to calculate how many hashes on average must be tried before one will "hit" a valid block? I'm talking about a single user (not a ...
Baard Kopperud's user avatar
8 votes
1 answer
2k views

Where exactly is the "off-by-one" difficulty bug?

I read through How is difficulty calculated? and want to understand where the "off-by-one" bug is in calculating difficulty. Here is a Matlab snipet I wrote to calculate difficulty. What are the ...
Cal Abel's user avatar
  • 131
7 votes
1 answer
6k views

How is a block header hash compared to the target (bits)?

I'm trying to wrap my head around the mining process by doing a small example of block hashing. According to the Wiki entry about difficulty, the target for a block hash can be read from the "bits" ...
NthDegree's user avatar
  • 235
7 votes
1 answer
5k views

What does the nBits value represent?

When a miner hashes a blocksheader and it produces a hash that is lower than the value represented by nBits then the PoW is considered solved. What exactly does this mean? For example a SHA256 hash ...
no nein's user avatar
  • 297
7 votes
1 answer
670 views

Why was the maximum target set to 0xffff0000000...?

Is there any specific reason why the initial target was set to this: 00000000ffff0000000000000000000000000000000000000000000000000000 Why not the maximum value for a 256 bit number: ...
inersha's user avatar
  • 3,053
7 votes
1 answer
2k views

Why does Bitcoin not have faster downward difficulty adjustments?

The BCash fork seems to have correctly anticipated the need to adjust difficulty downwards in the case of very slow blocks. This means it's much less likely for the chain to be orphaned when it was ...
Vijay Boyapati's user avatar
7 votes
3 answers
22k views

How does a difficulty increase affect a miner's income?

At the time I write this, there are a lot of people getting into Bitcoin mining for the first time. Many buy ASIC hardware and are later surprised that their mining income suddenly drops due to a ...
Dr.Haribo's user avatar
  • 8,429
7 votes
1 answer
382 views

How does one know they solved a block?

Having the difficulty (either in the "bits" form, big integer form, or human-readable format) and a given block hash, how does one know if they solved that block? What is the formula or algorithm for ...
ThePiachu's user avatar
  • 43.1k
7 votes
1 answer
2k views

How can I find the "real" difficulty on testnet?

As is well known, testnet has a "20-minute rule": if no block is found within 20 minutes, the mining difficulty drops to 1 until a block is found. From some experimentation, it appears that bitcoind'...
Nate Eldredge's user avatar
7 votes
1 answer
480 views

Is it necessary for blocks to record the nBits difficulty parameter?

The next difficulty to solve a block is determined from how fast blocks were solved before it. In addition, the difficulty only changes once every two weeks or so. So, couldn't every node keep track ...
morsecoder's user avatar
  • 14.1k
6 votes
2 answers
368 views

Why aren't block hashes used directly as scores for difficulty purposes?

Why does Bitcoin apply a difficulty function to block hashes and then use the output of this function to add up and determine the "longest" chain? Why not just e.g. add together all block hashes (as ...
Adam Ierymenko's user avatar
6 votes
1 answer
291 views

Why didn't the difficulty adjust for the first 30,240 blocks?

I'm working on showing the difficulty adjustments over time, and I've noticed that the first difficulty adjustment did not take place until block 32,256: http://learnmeabitcoin.com/explorer/node/...
inersha's user avatar
  • 3,053
6 votes
2 answers
6k views

Why is difficulty measured in a hash’s leading zeroes?

I understand how generating a SHA-256 hash containing any specified sequence requires lots of guessing and checking. The longer the specified sequence, the more rarely that it will appear. And I ...
Jacob Ford's user avatar
6 votes
2 answers
785 views

Is there a uniform measure of "difficulty", that when multiplied by price, will give "profitability of one hour of mining"?

I recently open Bitcoin Pie, a site that compares crypto-currencies. Given the exchange rate in BTC, I would like to add another column that tells "relative mining profitability", regardless of the ...
ripper234's user avatar
  • 26.6k
5 votes
2 answers
3k views

Isn't Bitcoin's hash target supposed to be a power of 2?

From Bitcoin's whitepaper I've gathered that the hash of a block must start with a certain number of zeroes. And that this number of zeroes is adjusted every 2 weeks. Consequently the hash target is a ...
Fred's user avatar
  • 133
5 votes
4 answers
6k views

When will next halving events occur?

I've read in some places that the next halving event will be on 2016. How can this be estimated?
knocte's user avatar
  • 1,754
5 votes
4 answers
2k views

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 ...
MaiaVictor's user avatar
5 votes
2 answers
2k views

Why would a miner mine with a difficulty other than 'the' difficulty?

Why would a miner mine with a difficulty other than the network difficulty? Both of these questions describe miners mining in such a way. What's the benefit of this? What even does it mean?
Kinnard Hockenhull's user avatar
5 votes
2 answers
19k views

How to select minimum difficulty when mining with Slush Pool

I am mining on a single Antminer S9 with Slush Pool. There is a setting called "minimum difficulty": When I read their manual, item #8 states The pool automatically assigns difficulty that ...
AstroSharp's user avatar
5 votes
2 answers
2k views

How does solving reduced difficulty hashes contribute to solving a block? [duplicate]

In pool mining, it's my understanding that miners solve a reduced difficulty hash which proves that work is being done and also simultaneously helps solve a block. How is this computationally ...
Steven Lutz's user avatar
5 votes
3 answers
10k views

Why is mining difficulty increasing?

I have heard in many places that mining difficulty is increasing, meaning that the hardware used to mine new coins will need to be more and more powerful as time goes on. What is pushing mining ...
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