# Questions tagged [block]

This tag should be used for questions related to Bitcoin blocks

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### 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 ...
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 ...
7k views

### What is the number of transactions in a block?

What determines the number of transactions that can be validated in a block?
17k 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 ...
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 ...
92 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 (...
29k 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 ...
15k 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 ...
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 ...
8k 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 ...
788 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 ...
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 ...
1k 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 #...
5k 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 cant find any information what this value is about. Request: getblock ...
4k 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?
1k 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-...
432 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 ...
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?
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?
2k 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 ...
3k 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?
1k 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. ...
5k 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.
416 views

### When miners are working on their block, does everybody's block have the same transactions in them?

On Bitcoin-Wiki's page about Blocks, it says that "Bitcoin transactions are broadcast to the network by the sender, and all peers trying to solve blocks collect the transaction records and add them to ...
383 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 ...
804 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 ...
88 views

### Is a timestamp in bitcoin different than just the “stamp of time”?

In the "References" section of Bitcoin's whitepaper, Satoshi Nakamoto points to three papers that serve as inspiration for digital timestamping. When you read those documents it is clear ...
85 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 ...
81k 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 ...
4k 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 ...
10k 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 ...
6k 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
6k 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 ...
8k 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....
2k 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 ...
386 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?
3k 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?
166 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 ...
316 views

### identical coinbase transactions

this sounds like an old topic but i have not found a satisfying answer yet; in history there lived two blocks with identical coinbase transactions: https://www.blockchain.com/btc/block-index/106662 ...
384 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?
2k 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?
2k 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 ...
225 views

### Which elements of a block are hashed?

Other than the previous block hash and nonce data, which elements of a block are concatenated in order to be hashed?
133 views

### What are the benefit of mining an empty block

Something peculiar just happened on the newly mined block number 655534, it contain only the coinbase transaction, nothing else. I have searched for a similar question but only found this one Why ...
110 views

### How is a “reward” encoded in a block?

If a miner creates a block including an appropriate hash value, then he sends it to all nodes, and each node verifies if this is correct or not and add it to the previous block chain if this is chosen ...
2k views

### What encourages Bitcoin miners to relay blocks?

Lets say I'm mining bitcoins, and I've just received a new block that someone else has mined. What encourages me to send that block to anyone else. I can understand how the original miner wants to ...
10k 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 ...
2k views

### Verifying Bitcoin ownership

Suppose Alice has 30 bitcoins from David. Now Alice wants to transfer amount 20 bitcoins to Bob. Now, Alice creates a transaction with Bob's bitcoin address. To prove authenticity and integrity, ...