Questions tagged [hash]

This tag should be used for questions related to hashes. A hash is the output of a hash function, a function which .is a mathematically reproducible but irreversible process that takes in an arbitrary length input and produces a fixed length output. The same input will always result in the same output. Hashing is central to Bitcoin mining as well as the generation of Bitcoin addresses.

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60 views

I've built a bitcoin miner and mined. Now what I do?

I've mined bitcoin to test and understand cryptocurrency better. Which generated this hash 00000431fb66ed96815b3829e975c2235a64b9a646c0bd1cc526dc1727c1f16b(nonce value of 300712) What I do with this ...
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Detecting BTC transaction hash data: help

please I need some help in reading the hash data correctly. Given below transaction of total value btc 1.55821903 https://www.blockchain.com/btc/tx/...
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BTC invalid transaction: double spending attempt?

I'm writing because I need some help in understanding the below hash data. Thank you. https://www.blockchain.com/btc/tx/976e6d64a4c98cf15ac917b98a04333f896b7cd15c1f2fdfb18f6fee668b670c Is it a double ...
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1answer
26 views

Size of seed used in murmur3 hash BIP0037

I'm trying to implement a seeded murmur3 hash using the bip37 standard for use in bloom filters. In hash.cpp in bitcoin core, the seed is an unsigned int value. However my understanding of bip37 to ...
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1answer
51 views

What exactly is signed in "prev_out"?

What is signed by scriptSig? I use my private key to sign data from the unspent transaction? I sign the "prev_out" object? I read that the signature in "prev_out" is there to ...
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25 views

More than one possible nonce [duplicate]

Assuming currently we need 19 leading zeroes in the hash. Assume that for a block, minimum nonce possible for getting 19 leading zeroes is 12300, but a pool/miner returns 32330 as a nonce (which also ...
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1answer
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What hardware do pool operators use for calculating the hashmerkleroot?

I've reviewed the response here: How do pool operators do their hashing? and acknowledge that the ratio of hashing required by pool operators is incomparable to the miners. I still wonder what ...
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1answer
39 views

Changing the blockchain requires more than just recalculating all hashes..?

New here! I read this everywhere - "To change some data in a blockchain, the malicious user will have to recalculate hash for every block starting from that particular block". My doubt is - ...
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Is there a list of processes within Bitcoin that use hash functions?

Hashing within Bitcoin is done in several different areas of the code. EG: We have the SHA-256 mining algorithm, the Merkle tree hashing, and I believe double hashing within certain areas (SHA-256D). ...
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For a block containing 'x' number of unverified transactions, how many SHA256d hashes are performed to obtain the hashmerkleroot?

I've been trying to understand this for a few days now. I understand that the hashmerkleroot is the root node of a fully perfect binary tree. I also understand that the sha256d hashes would be the non-...
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What is the difference between hash-target and the previous hash? [duplicate]

Is the target that the requirements have to meet a number that is set by the network that is always the same, or is the target the hash from the previous block?
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Is the block header the data that gets hashed or is it the info of the transactions that get hashed? [duplicate]

I just need to know what is the data that gets hashed. Also if the nonce is put from the beginning or if it's only out if it doesn't meet the requirements of the target. Thanks.
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elderly mom transfrred bitcoin out of coinbase but doesn't know where it went ... have identifiers and hash stuff

My mom is and she transferred bitcoin out of her coinbase account which we finally regained access. She does not know where she transferred it to, i.e., a wallet, or other account? We have the ...
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What parts of a block, other than the nonce, can a miner vary

What are the list of all the variables whose values that the miner can cycle or modify to get a valid hash for this block (with very high probability) ? The only one I am aware of is: Nonce - 4 Bytes....
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1answer
152 views

Why tagged hash repeat the tag twice?

I noticed that the hash message for the tagged hash in BIP340 is prefixed with SHA256(tag) || SHA256(tag), which also describes the reason Because this is a 64-byte long context-specific constant and ...
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39 views

how to do sha256(sha256(modified transaction)) and find z1 and z2 value

hi I tried to get z1 and z2 value but I cant understand. can any one help me with example for finding z1 and z2. or alternate website for 2coin.org example: see this trans. Two identical R value ...
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2answers
78 views

What data is hashed to produce the block hash?

Exactly which items from a block are included in the data that is hashed to produce the block hash?
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1answer
69 views

How a real mining code treats difficulty?

I have come up recently with "how to mine bitcoin using python" or "how to mine bitcoin using golang" and as I have been observing all these source code, not only I'm confused but ...
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Estimate total number of hashes Chapter 10 "Mastering Bitcoin" [duplicate]

In Chapter 10 of "Mastering Bitcoin", the Author writes "With this level of difficulty, a single miner processing 1 trillion hashes per second (1 terahash per second or 1 TH/sec) would ...
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2answers
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Merkle tree hash - Computing hash manually doesnt match the one computed by SHA256D64

I am trying to go through the code to check the merkle tree hash computation done by BlockMerkleRoot in bitcoin core. The hash computed using online tools by appending transaction hashes is different ...
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2answers
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How can we derive all work ever done on the system from the lowest hash ever found?

If not mathematically (I imagine the proof might be quite rigorous), could you please provide an intuitive explanation for why the lowest hash ever found tells approximates the total amount of work ...
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1answer
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How do you generate a Bitcoin wallet by hand?

I am interested in the exact process for generating the various components of a Bitcoin wallet by hand. Specifically, the components I'm interested in are: Private Key Public Key Public Key Hash ...
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Python Code - import error : cannot import name "privtopub" from 'bitcoin'

Hello everyone when I start this code on PYCHARM looks like no problem. But when I turned this code from python to exe and exe don't start and it says: import error: cannot import name "...
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2answers
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Where can I turn the unique hash result of SHA256 to bitcoin?

i watched on youtube from 3Brown1Blue channel about "how bitcoin works", it said what makes bitcoin valued is come from the unique hash result of SHA256. for example if someone put string to ...
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2answers
445 views

how do i brute force my wallet.dat to get my private key

i am not really a computer programmer, but i want to get my private key from my wallet.dat, i have just the wallet.dat file and the public address where the bitcion was send. From my previous ...
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How can I transfer unconfirmed transactions from wallet.dat to a new blockchain wallet

My question may not be very clear since I’m not really an expert in bitcoin and its technology. But in my possession I have just a wallet.dat files with an unconfirmed transaction on it. I followed a ...
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2answers
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How Bitcoin restricts the mining time?

How Bitcoin restricts the mining time? We know cryptocurrency systems restrict the mining time of a block to a certain limit for security reasons. For example, mining time for Bitcoin is ~10 minutes. ...
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Looking for feedback on (Browser-based) Blockchain Simulator

I have created a Blockchain 'simulator' in JavaScript, for the purpose of helping explain how the technology works. It is complementary to a website I have set up years ago, where I attempt to explain ...
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cannot generate bitcoin first block

I have download bitcoin source and change genesis in regtest. and i try to generate 1 block by command ./bitcoin-cli -generate 1 it does not show any mining block. i try over 10 times but it is still ...
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How does a blockchain relying on PoW verify that a hash is computed using an algorithm and not made up by a human?

How does a blockchain verify that the hash provided (the one with the leading zeros that is supposed to be unique, computed using lots of processing power) is indeed unique and that it wasn't just a ...
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0answers
29 views

Is the block header in stratum protocol double hashed?

I'm trying to understand how the block header is done when mining in a stratum pool. Should the block header be hashed once or double hashed ? the block header consists of the version, previous hash, ...
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1answer
26 views

What exactly happens to leaves when forming nodes?

If you hash TXIDs with sha256 twice, you get the leaves of the merkle tree. As far as I understand the two outputs of the TXIDs are concatenated / paired. What does that mean? Are they added together?
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1answer
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BTC on blockchain

I see my Wallet address on the Blockchain but it says spent and what does that mean? It did not arrive to the wallet i sent it too! I need it to be located and returned or sent to the wallet i gave.
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RegTest Genesis Error

how to generate regression test genesis block ? i saw in bitcion nonce is 2. but i generate from GenesisH0 it not showed nonce 2. for other altcoin i saw nonce is 0 why ? how to generate it ? python ...
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Bitcoin leading zeros as difficulty [duplicate]

Does it necessarily have to be leading zeros that determine the bitcoin difficulty, is it possible to use lets say 9 zeros at the end of the hash to determine difficulty as well.
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1answer
128 views

How to generate a coinbase transaction?

I am creating a miner in C++ for solo mining, and am struggling to create the proper coinbase transaction. Say I have a bc1 address, like bc1qfc7fameteuguetm0kfzypnvf2ju6wppdvj6tkc , what would be and ...
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Regardless of how bad it is for the network, wouldn't mining an empty block be signifigantly less work? [duplicate]

A block contains the previous block's hash, a nonce, and series of transactions. That information needs to be hashed until the block's hash meets the number of leading 0 requirement. My question is, ...
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1answer
132 views

how to hash block header in c++

I want to hash a block header in C++ but dont know how. Im just using a test block at the moment, so that I know what the expected outcome is. https://www.blockchain.com/btc/block/669892 I have a ...
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137 views

How do I hash header block with C++

So im trying to hash a header in C++ and I am having some trouble. I have tried different libraries (cryptopp, openssl) cant seem to hash the header correctly. This is the block which I am testing: ...
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How is the Target Hash determined?

So, I understand how the amount of leading 0's are calculated, but how is the hexadecimal that come after the leading 0's calculated? For example, the previous mined blocks hash was ...
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1answer
139 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 (...
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Calculating P2WKH nested in P2SH addr/redeem script hash from pubkey

My calculation of the hash160 doesn't seem to be correct - what are my sins? Tx spending the input: https://www.blockchain.com/btc/tx/d490cc0a5b9799e09b02dd4b20a6d7ca297c09c425983efc13b382f6023d0376 ...
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1answer
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How difficulty increases to get the lucky hash in blockchain? [duplicate]

Currently first 19 zeros are required in bitcoin block hash which has become very hard. How this zeros are being controlled to increase? If it is dynamic what are the factors which has influence to ...
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1answer
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What is the practical link between the hashing power in the bitcoin network and its security? [duplicate]

Several books claim that as the hashing/computing power increases, the bitcoin network is securer. How can a non-techie sees that from a practical standpoint?
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Does bitcoin mining pool hash randomly and separately

When it comes to hashing does each mining entity use total random seed for each of their hashing function or do they have a range like " Im gonna cover from 0 to 500, and you cover from 500 to ...
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1answer
80 views

Three different HEX having same wallet address how possible?

HEX1: 1111111111111111111111111111111111111111111111111111111111111111 public key: ...
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1answer
52 views

With the right technology, could the entire blockchain be rewritten?

Imagine that someone had access to an alien super computer such that they could mine any block in nanoseconds. At that point, could that person create a chain with the same BTC genesis block, generate ...
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1answer
68 views

Stealing a correct hash because of an invalid block

Suppose that a miner find the right hashes but involuntarily or by malicious intention then create an invalid block, like trying to double spend a transaction My guess is that the moment this block is ...
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1answer
83 views

Will a recursive sha256 run over all 2^256 inputs before a collision?

Will a recursive sha256 run over all 2^256 inputs before a collision? Here'a a python program showing my question - will this loop for 2^256 times - given endless memory or will it terminate before - ...
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1answer
1k views

Adding instead of concatenating hashes in Merkle trees

Why aren't the hashes combined using a commutative operation such as addition instead of concatenating them? Any possible vulnerabilities or security flaws? thanks for your time and efforts.

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