Questions tagged [block-header]

The block header is a portion of each block in the block chain that identifies the basic parameters of that particular block such as the block version, the time it was generated, the hash of the previous block, and the hash of the transactions in that block.

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23 views

What is the proper way to handle reorgs when fetching headers

I work on bitcoin-s, and we've found a problem where if a node is stopped with it's chain tip being a one that is later reorged out it will not be able to continue syncing headers. This happens ...
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Merkle root with one transaction

I am trying to build a merkle root which contains only the coinbase transaction from bitcoind After creating the coinbase transaction i need to convert it to little endian, hash it twice and then put ...
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Can I get all block header data like the SPV node?

It hasn't been long since I studied Blockchain. I only need header data, not all block data, for study purposes. As far as I know, the SPV node stores only the block's header information. Can i get ...
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What is the optimal way to increment extranonce?

I'm trying to learn how to block headers are created and an efficient way of doing so. Given a list .of transactions, can I change the extranonce without having to rehash the entire list? EDIT: To ...
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Padding the blockheader in sha256

The block header size is 80 Byte (640 bits) so we must pad it to a multiple of 512 (In our case to 1024) like this: (blockheader in binary)+1+00000.....000+1010000000 where "1010000000" is ...
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How to build coinbase transaction from bitcoin core?

I am coding a program that connects to bitcoin-qt as local server. For building the blockheader i need the merkleroot, to build the merkle root, i need the coinbase transaction (which is not provided ...
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A Bitcoin soft fork idea to help compress the blockchain

I've thought about a soft fork that can help storage costs. Why don't we force miners to embed the height of the TX Merkle tree in the first two bytes of the 4-byte block header version? It would ...
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1answer
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Calculate BitcoinGold Block Header Hash [closed]

I am trying to calculate block hash # 632295 { 'version': 536870912, 'prev_block_hash': '000000017590609fd72cadc5fd05732cfa1760bd882213afbb7b788c42e115c8', 'merkle_root': '...
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Block 620826 is 1 second before block 620825?

How does that happen? Obviously the miner of 826 built his block on top of 825, but why is the time 1 second earlier?
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3answers
263 views

Get transaction data from full node

Background Information I am building an application that requires the ability to query any bitcoin full node (from a python script using raw tcp sockets) in order to read the OP_Return value listed ...
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207 views

How to get block header hex?

I am trying to research hash functions and I want to be able to use bitcoin's mining outputs as hashes. I am curious about where the actual hex value of the data that generates that hash with a lot of ...
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Which block header fields are miners able to change in an effort to avoid having to recalculate the Merkle Root?

In addition to the nonce and the Merkle Root, there are 4 other fields in the header - version, previous header hash, time and nbits. Assuming a miner does not want to change the merkle root because ...
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How to dissect or decode a BTC transaction?

I used a packet capture to capture the transaction of bitcoin, and I got the following: ...
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bitcoin's PoW, real time of creating one block

i learn that bitcoin is created every 10 minutes and if block is created faster than 10 minutes, Difficulty will increase. and study deeper, mining process is finding nonce that start 0 to increase 1 ...
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What is the most optimal way to parse a raw bitcoin block with python?

Let's say one is connected to a zmq socket and listening for rawblock. How you'd parse the block header is as follows: block_header = raw[:80] version = block_header[:4] prev_merkle_root = ...
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Can a full node provide a bogus block bloomfilter to a Neutrino node?

When a thin client using BIP157/BIP158 (Neutrino) requests the block filter for the latest block, would it be possible for the full node serving this request to attack the Neutrino node by providing a ...
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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 ...
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1answer
718 views

Unusual Version Number in Blocks

I've noticed recently that some blocks contain version numbers that are not the traditional 0x10000000 or 0x20000000. For example, this block, has a version number of 0x3FFFE000 instead of 0x20000000 ...
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Significance of the “hash” field reported by the 'bitcoin-cli getblock' command

It is stated that the header of a block does not contain a 'hash' field ( see https://en.bitcoin.it/wiki/Block_hashing_algorithm or Antonopolous' Mastering Bitcoin 2nd Ed. ) This makes sense since ...
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Merkle root Vs transaction hashes

It is not clear to me, why not we can simply store transaction hashes in a block header instead of storing the Merkle root. I understand that storing transactions' hashes will slightly increase size ...
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Is my understanding of Blockhain Endianness correct?

I know questions on this topic have been asked to death in a number of different ways. I also know that what endian order refers to specifically is dependent on context. What I want are some ...
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1answer
415 views

Why there is no block index or block height included in the block header?

Why block index or block height is not included in the block header? Do we have to go through the whole chain if we want to know how many blocks are there in a chain? On the other hand, if some blocks ...
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1answer
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What should be less than the target?

When I go to BlockExplorer and observe the hash of block 514441's header I see it to be: 0000000000000000004ec916884d8b2cd3dc0e80ab199cc23e528e7dc10fafc6 However when I obtain the header of block ...
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When computing the hash, do you need anything after the number of difficulty bits?

I'm going to screw up a lot of the terminology here. I'm trying to understand the Bitcoin algortihm and wanted to use this JS miner -- https://github.com/howardchung/jsminer . Specifically, I'm ...
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Are there any blockchain explorers that provide raw Tx data and block headers?

I've looked at some of the more popular blockchain explorers, but none of them seem to provide the feature I'm looking for. I'd like to find a blockchain explorer that allows you to see raw Tx data ...
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What is the difference between Root Hash and Block Hash?

I was reading about how Bitcoin works from Satoshi's original paper. I had a query while going through the 7th paragraph. What is the difference between Root Hash and Block Hash? Isn't the block hash ...
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Bitcoin Blockchain Parser to get all block headers

I am looking for on-line or off-line run Bitcoin Blockchain Parser to get all block headers only All I need is ########## Block Header ########## Version: 1 Previous Hash ...
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1answer
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Calculate hash of block header

I'm trying to calculate the hash of block #502871. This is the block: { "result": { "hash": "00000000000000000020cf2bdc6563fb25c424af588d5fb7223461e72715e4a9", "confirmations": 35, "...
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1answer
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Why do block explorer APIs say the nonce in the block header is 0?

Several block explorers are reporting that the nonce value in many block headers is 0. For example, blockcypher, Why does this happen? Where can I get the actual block headers?
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351 views

Do you know any download site for full blockchain header data (6) in CSV ASCII format?

do you know any download site for full blockchain header data (6 variables) in CSV ASCII format ? I would like to enter block header data for every block from No.0 to latest into mining simulator to ...
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Help in understanding block header input data for scrypt

I am an computer engineering student trying to understand how the Litecoin scrypt algorithm works. I downloaded the Github cp-uminer. Can someone give me some examples what the input data look like ...
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1answer
670 views

How is mining difficulty defined (formula)?

The result of sha256(s) that miners attempt is a 256 bits long number (64-digits hexadecimal number). I understand that this 256bits number should be lower than the target threshold, the target ...
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1answer
425 views

Merkle Root for 1-transaction block!

I know that merkle hash for one transaction tx is: sha256(sha256(tx)) In this block: https://blockchain.info/block/000000000000000001291219dde8ed705903e8c101f416c68a439e5171ede5bc there is only one ...
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1answer
552 views

merkle root 2 codes

While trying to calculate the merkle root in python from the data i got from the mining pool.... i found there are 2 different codes. code 1: def build_merkle_root(coinbase_hash_bin, merkle_branch):...
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Mining Block header bit reversing

While trying to understand the mining process and checking in python..... i am puzzled with which info from/to pool are in Little Endian, which one needs reversing in building the block header + ...
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1answer
186 views

Hash that defines previous block in Blockchain vs mathematical solution

Is the hash that defines the previous block (block A) in a new block (block B), the same as the hash the miner calculated to submit block A? As far as I know, you need to find a nonce so that the ...
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How generate a hex string for a block

I have written this code to create and submit a new minned block to the bitcoin network: unsigned long magic_number = 0xD9B4BEF9; unsigned long block_size = 89 + (strlen(coinbase_transaction)-1) +...
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1answer
6k views

To create a blockchain using MySQL database

I want to create local blockchain for my application. New blocks should be created while giving reference to previous block. But I am not getting exactly how will I do it in MySQL? I got some idea ...
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1answer
1k views

How to generate a block header?

good afternoon I set myself a task to understand the work of the miner, but as you understand it is difficult for a beginner. Constantly there are questions. Without conditionally, I turn to Google ...
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1answer
911 views

how to convert blockchain to new version?

I have altcoin bassed on old Litecoin sources, end i try to convert it for latest available sources. How i can do this ? What need for this ? I try simple download it on old wallet, then run new. But ...
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1answer
1k views

Is the hash of the previous block included in the block header?

What the title says above, but for more clarification I am asking whether the hash of the previous block header is part of what is hashed to create the header of the new block? Like what are all the ...
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1answer
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How does Segwit prevent ASICBOOST?

I know that ASIC BOOST exploits the fact that the blockheaders are not a multiple of 64 bytes, but what is the change in Segwit that prevents this? Are they always a multiple of 64 bytes now for ...
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1answer
333 views

How can miners alter timestamps to prevent or delay BIP09 feature activation?

In bitcoin mailing list , a proposal had the following concern. BIP 09 is vulnerable to miners fiddling with timestamps in a way that could prevent or delay activation - for example by only ...
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101 views

Does the 1 MB block size limit include the header?

I was able to follow the code to validation.cpp: // Size limits if (block.vtx.empty() || block.vtx.size() > MAX_BLOCK_BASE_SIZE || ::GetSerializeSize(block, SER_NETWORK, PROTOCOL_VERSION | ...
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What is a nonce?

When I see the block info on blockchain, I see that there is a field named "nonce", I could not find any relevant information on web regarding what a nonce is. Please explain what a nonce is what is ...
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1answer
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Creating a P2P network like Block Chain

Posting this in Bitcoin community because I believe that you guys would be the best to answer the question since my question is related with the blockchain. I am wondering how to create a P2P ...
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1answer
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How a Light Node can get a block?

I'd like to better understand how a light node can retrieve a complete node. If I understood correctly, I can consider a light node a node which is part of the peer-to-peer network that receives and ...
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1answer
292 views

SPV clients - how much does occupy the full blockchain headers?

Does a spv client need to download the full blockchain headers? how much does it occupy? is it better for security? I saw a blockchain-headers file in my android wallet that only occupies -30MB.
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Is the miners address part of the block or the block header? [closed]

Should the following be sufficient merkle root, block number, previous block hash, timestamp and nonce?
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How is the mempool incorporated in the calculation of the block hash?

So I've been reading about how the nonce is calculated. There is one part that I don't get. So there is a mempool, and each node (or mining node) takes a part (or the whole part) of that mempool, ...