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Questions tagged [block]

The components of the blockchain and a data structure that collects transactions.

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22 votes
1 answer
8k views

What is the expected time until the next block is found?

https://bitcoin.stackexchange.com/a/3908/659 says: Luckily, you'll only have to wait five minutes on average for a block to be found (blocks are one every ten minutes, so the expected delay until ...
Chris Moore's user avatar
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2 votes
1 answer
446 views

How does solving a block work in relation to the first letter/number after the 0's?

I did a terrible job of explaining it in the title so I'll explain here. Say the target hash to solve for a block is 00004aef... etc. does that mean that you can't solve the block if you get 00005fad (...
L M 's user avatar
  • 79
17 votes
4 answers
9k views

What is the number of transactions in a block?

What determines the number of transactions that can be validated in a block?
anapaso's user avatar
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15 votes
2 answers
11k views

Why can we have small fractions of a Bitcoin?

I didn't study the inner workings of Bitcoin (yet), but already since when I just started using it, I wondered why a Bitcoin can be split up in parts. Because there is a limit on the amount of Bitcoin ...
Steven Roose's user avatar
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1 vote
1 answer
768 views

In what format does a block store the transaction data?

Does it store the raw transaction data literally like (excuse the formatting inaccuracies): 0x24134i59435ej3...9 sends 0x9wri03vw3sdfsd...i 26.00000023423 Bitcoin. Or is it stored differently?
Jamo's user avatar
  • 167
18 votes
4 answers
18k views

Why does each block store a Merkle root?

I understand how a Merkle root is calculated and stored in the block. But how do miners verify a transaction using the Merkle root? Here are 18 conditions that verify a transaction. None of them uses ...
Mohit Munjani's user avatar
12 votes
2 answers
8k views

What is chainwork?

If I run the RPC call getBlock on the bitcoin-qt client it gives me field called chainwork containing a hash. I can't find any information what this value is about. Request: getblock ...
Dennis Kriechel's user avatar
10 votes
1 answer
30k views

Whats the process of Creating a Block on the BlockChain

have been mining on pools and blindly going a long for the ride of > generating a block Can somebody walk through the process in simple terms of the steps involved in creating a block on the ...
BitCoin New Guy's user avatar
5 votes
1 answer
1k views

What is a block?

I know bitcoin has a block chain that is from my best representation a list of blocks. I know the block holds many transactions. But i'm still very much lost as to what a block is and how a block can ...
Patrick W. McMahon's user avatar
2 votes
1 answer
659 views

What are the components of the raw block shown in this image?

I'm wondering what the portion between the block header and the transaction data (the un-annotated section) is. I can't seem to find any information on it.
Jamo's user avatar
  • 167
25 votes
1 answer
16k views

When a block is "discovered" how is the nonce determined?

I know that a block is based on a random number called a nonce, but if that number is random and unknown to the miner, how is that number actually verified as the correct nonce and not some arbitrary ...
Andrew's user avatar
  • 251
13 votes
3 answers
9k views

What is the exact formula for calculating transaction fees?

According to the Wiki: If the blocksize is more than 250 kB, transactions get increasingly more expensive as the blocksize approaches the limit of 500 kB. Sending a transaction when the blocksize ...
ThePiachu's user avatar
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12 votes
2 answers
851 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
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11 votes
5 answers
2k views

Which is the smallest hash that has ever been hashed?

Let's assume, the hash 00000000000000000024c0bdbec66a889778c00bc69be0a96cbbd98b75c3ce09 of block #499644 is smaller than 0000000000000000002d429f39afec70c938e888c3417d690bbc85e83529991c of block #...
hardfork's user avatar
  • 2,117
8 votes
2 answers
2k views

Why does the blockchain need blocks?

I think I understand the main parts of the Bitcoin blockchain. While I was explaining the concept to my girlfriend she asked me why groups of transactions are actually stored in a block? Every ...
kramer65's user avatar
  • 315
23 votes
2 answers
5k views

What are the arguments for and against the increase of the block size limit?

Can someone give a quick point by point list, what arguments the proponents and opponents of increased blocksize have for their case?
user23381's user avatar
  • 233
21 votes
5 answers
11k views

Shortest and Longest block interval time ever recorded in Bitcoin

Bitcoin block interval time is on average 10 minutes, that is the difficulty is adjusted in such a way that every 10 minutes a miner will manage to find the right hash. This is just an average time ...
Rexcirus's user avatar
  • 381
19 votes
2 answers
2k views

What happens when a miner does not claim all fees/generated coins?

Suppose that a miner for some reason has the generation transaction of their blocks not take all the possible coins. This can happen for a variety of reasons, almost all of which are bugs: An off-by-...
Daniel H's user avatar
  • 684
18 votes
3 answers
9k 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
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17 votes
2 answers
3k views

What's the purpose of a maximum block size?

Bitcoin has a maximum of 1 MB of transaction data in each block. Why is this limit present? When was it added? Was it intended to be temporary?
Nick ODell's user avatar
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7 votes
2 answers
2k views

When does a miner decide to stop collecting transactions and start calculating hashes to try to win?

I am confused about whether a miner chooses to wait for more transactions (more fees) or starts as soon as it receives the first transaction from the network. Once a miner has started calculating the ...
Peter Mel's user avatar
  • 625
6 votes
2 answers
450 views

Do transactions affect the discovery of a block?

When a miner creates blocks, do transactions in that block affect the result? For example, if a miner creates a block, but now a new transaction is broadcast on the network, will the miner stop ...
kakahong's user avatar
  • 149
3 votes
1 answer
298 views

Is there a correct way to refer to "orphan" blocks?

I was reading a passage on the bitcoin wiki that pointed out that it doesn't make sense to call invalid chains "orphans," since, by definition, every block in the blockchain except the ...
Nick ODell's user avatar
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1 vote
2 answers
201 views

1 MB Block Size as a Anti-DoS Attack Measure

Wikipedia explains the rationale behind the 1 MB block size limit as follows: The one megabyte block size limit was added in 2010 by Satoshi Nakamoto as a temporary anti-DoS measure A SE post ...
S.O.S's user avatar
  • 419
16 votes
1 answer
5k views

Where is the UTXO data stored?

When a new transaction is received it is added to the memory pool (after checking for conflicts). While mining, only the transactions which are in the pool are considered. What happens to the ...
somesh's user avatar
  • 457
16 votes
2 answers
4k views

Bitcoin Block Size - What are the rules?

What is the maximum size a block can be? Is there a minimum size? Can you have a block with 0 transactions included?
Michael Pickens's user avatar
15 votes
2 answers
6k views

How do you make a Genesis block?

What is involved in creating a genesis block? What makes it different from the other blocks in the chain.
user4381's user avatar
  • 151
9 votes
2 answers
3k views

How to prevent a miner from stealing another miner's block?

Many articles only contain a phrasing like A miner A solves the hash problem and gives the result to the network to check. Once a majority of the network confirms, A gets the reward. But how does ...
Mithril's user avatar
  • 333
6 votes
1 answer
484 views

What is the different between CompactSize and VarInt encoding?

Pieter Wuille's definition of CompactSize encoding seems to match Greg Walker's definition of VarInt encoding, yet the BitcoinWiki claims that CompactSize is not to be confused with VarInt. What, if ...
drogos86's user avatar
  • 147
3 votes
1 answer
2k views

Pruning the branches in Merkle Tree

In Merkle tree, leaves are actual transactions and internal nodes are hash of their childrens. In the Bitcoin paper, Satoshi talks about pruning branches in the Merkle tree to save storage space. ...
Curious's user avatar
  • 295
3 votes
1 answer
1k views

After Segwit Activation, what is the largest block size possible?

The code says MAX_BLOCK_SERIALIZED_SIZE = 4000000, but that is actually not a actually consensus rule as stated here: https://github.com/bitcoin/bitcoin/issues/10289 The actual consensus rule is ...
Jimmy Song's user avatar
  • 7,759
3 votes
2 answers
433 views

Energy to confirm one block?

What is the minimum energy (or CPU operations) required for someone to confirm one block on their own, to launch a double-spend attack? How can I calculate this from the current difficulty or ...
user1009013's 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
15 votes
1 answer
8k views

What is the magic number used in the block structure? [duplicate]

What is the Magic no used in the block structure, why is the value always 0xD9B4BEF9 and what is it used for ? Thanks
user1892955's user avatar
14 votes
1 answer
12k views

How to get a bitcoin address's balance?

I know blockchain.info has an API: https://blockchain.info/q/addressbalance/134dV6U7gQ6wCFbfHUz2CMh6Dth72oGpgH gets the bitcoin address's balance,but it's not open source and must connect to the ...
Gank's user avatar
  • 275
12 votes
4 answers
10k views

Which is the relation between transactions and blocks?

I don't quite understand the relation between a transaction and a block. I imagine it as a list of blocks, and each block having a list of transactions but I have some doubts. When I do a transaction....
Macarse's user avatar
  • 527
12 votes
1 answer
4k views

Has any illegal data been saved in the Block Chain?

Has any illegal data been saved in the Block Chain, such as an illegal number, or illegal prime?
ThePiachu's user avatar
  • 43.1k
10 votes
2 answers
3k views

What would happen if two blocks had the same hash?

Consider the following scenario: January 2016 block A gets submitted. Its hash is 0001010. January 2017 block B gets submitted. Its hash is also 0001010 (collision). 10 minutes later, block C gets ...
Peter111's user avatar
  • 277
7 votes
2 answers
3k views

Do I need to keep all blocks when running Bitcoin Core?

Do I need to keep all blocks, from block 0 up to the current one, when running Bitcoin Core, either as a full node or not? Or can I just keep the more recent blocks to save space?
Geremia's user avatar
  • 4,672
7 votes
2 answers
1k views

What is the Block 1,983,702 Problem?

The issue, transition to requiring block height in block coinbases, was discussed back in 2012, however I just stumbled upon it, and would like to understand more about its significance.
BitcoinFanatic's user avatar
6 votes
2 answers
5k views

The role of timestamp

In Satoshi’s original paper, it is written that “we need timestamp to prevent double-spending”. However, I think timestamp is unnecessary, because every block has a previous block hash and merkle ...
Rubertos's user avatar
  • 227
5 votes
2 answers
2k views

Can a miner set the EXACT timestamp of a block?

I know that miners can adjust the timestamp of a block, but can they control the exact timestamp datetime (within the +-2h rule)? For example: A miner mines a block at 2013-08-08 08:01:34. Can the ...
user6266's user avatar
4 votes
2 answers
3k views

Which cryptocurrency has the smallest block time?

What is the lowest block time of any cryptocurrency? I don't mean the time of an individual block, but the target time per block. What is the shortest reasonable block interval?
MagikCow's user avatar
  • 217
4 votes
1 answer
739 views

Is the ordering of blocks in the rev*.dat files same as the blk*.dat files?

I understand that blk*.dat files save the blocks in the order it gets them from it's peers. Is the rev*.dat files in the same order as the blk*.dat files? For example, would the 400th magicbyte in ...
kcalvinalvin's user avatar
3 votes
1 answer
469 views

How is network time enforced?

I've seen how nodes gather network time data, but how is it enforced in the blockchain? Are all of the timestamps digitally signed and included in the block as proof?
user avatar
2 votes
2 answers
441 views

How are TXIDs determined from the raw hex data of a block? Also, what is the coinbase transaction?

Consider the hex data of block 170. The coinbase TXID is this: b1fea52486ce0c62bb442b530a3f0132b826c74e473d1f2c220bfa78111c5082 and the second TXID is: ...
Jamo's user avatar
  • 167
2 votes
2 answers
184 views

testnet3 frequent tx malleability

Related How confirm my own doublespend transaction got confirmed This is not about double spends and I believe that the related question is not about double spends ether! On bitcoin's testnet3 I am ...
Ben Muircroft's user avatar
2 votes
3 answers
4k views

Block Validation: who does it? How much it costs? And is it present in all protocols?

Different threads were posted in order to clear up this question, but there are some points that I would need to confirm: When you become a full-node (NOT miner, you just downloaded the full ...
3Chicken's user avatar
2 votes
1 answer
424 views

Will old accepted blocks ever be removed?

Or are they kept forever such that the chain from the Generation Block will always remain verifiable?
Tobias Kienzler's user avatar
1 vote
1 answer
326 views

How can an attacker change the address to receive someone's reward

At the end of my lecture, my lecturer asked a question that we never had time to cover: A miner creates a block A, which contains address b, on which they want to receive their rewards. An attacker ...
Krzysztof Jaminski's user avatar