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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1answer
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How do I get hash to verify transaction?

If I have the public key and signature for a transaction how do I get the hash value that is used in verify(hash, sig, pubkey). I want to know how to work backwards from a raw transaction to get it, ...
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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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1answer
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Is there a CUDA binary to convert a brainwallet string to a BTC address?

I am looking for a CUDA program which will take a single argument, a brainwallet password, and output a BTC address. After reading through several threads on how to convert passwords to public keys, ...
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Longest unconfirmed transaction?

I recently tried to make a transaction with coinbase. In a hurry I put no fee though. It's still unconfirmed and blockchain.info doesn't recognize my hash. But my btc qt wallet is debited. My question ...
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1answer
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The warpwallet challenge 2

here you can find a public challenge aimed to brute force a brain wallet private key, derived from 8 char long [a-zA-Z0-9] passphrase with a salt of "a@b.c". Is it possible to adapt an hashing ...
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2answers
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Generate private key from a bip-39 seed phrase?

I'm able to generate a new private key and associated public addresses using bitcoin-core, but what I really want to do is generate a new private key from a 24 word seed phrase. I'm not sure how to go ...
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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
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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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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 #...
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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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2answers
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Is verification of a blockchain computationally cheaper than recreating it?

One of the advantages of cryptocurrencies like Bitcoin that is often repeated is how hard it should be to manipulate past transactions. The reason that is often stated is that you would have to re-...
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What complexity class is Bitcoin's proof-of-work (hashcash) in?

To formulate this question precisely, I will define an idealized hypothetical "perfect" hash function H(n) which has nice scalability properties, and will formulate a problem PERFECT HASHCASH in terms ...
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2answers
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Two blocks, two transactions, same hash

Would a block containing a transaction with an identical hash as a previous transaction be considered valid? That is, if someone made a transaction for generating Bitcoins and solve two blocks with ...
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5answers
9k views

Where is Double hashing performed in Bitcoin?

where in the Bitcoin Protocol is SHA256(SHA256(x)) performed and why?
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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
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Proving collisions on Bitcoin addresses without discovery of the private key?

If there is a private key that leads to a collision on an address, it is possible to show that the private key is not the one used previously, even though they have a collision on the address? ...
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3answers
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How Bitcoin handles addresses collisions?

Since the addresses are hashes of a public portion of a public/private ECDSA keypair, what would happen to two different people with different keys that hashes into the same address? How would ...
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1answer
76 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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What are the sources of entropy in blockchain

I have little understanding of what entropy is and its specific role in blockchain. What I understand is that they're sources of randomness. From that, I'm able to infer these sources in blockchain ...
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1answer
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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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6answers
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How do you perform double-SHA-256 encoding?

The Bitcoin Protocol-specification gives an example of double-SHA-256 encoding. hello 2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824 (first round of sha-256) ...
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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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2answers
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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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2answers
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How to find Reused R values

I use software from https://github.com/ca333/rng-scanner , I try to find r that is reused. from the software I found results Bitcoin Address : 1GQdrgqAbkeEPUef1UpiTc4X1mUHMcyuGW In Input NR : 141 ~ ...
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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
688 views

How can I find a hash with leading zeros

I came across a similar question that was asked but the answer didn't seem quite complete. Coding is completely foreign to me and I have spent some time trying to solve with no success. I am trying ...
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3answers
458 views

ASIC-Resistant Proof of Work

Bitcoin uses a Proof of Work algorithm that makes it the perfect victim of ASIC mining. As a result, it is not very decentralized (more than 50% of Bitcoin's hash power is concentrated in China and ...
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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
263 views

ScriptSig content during signature (quadratic hashing)

As far as I know, the quadratic hashing problem came from the fact that every time a transaction is verified (or signed), the "unsigned transaction" that is hashed and verified changes depending on ...
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1answer
391 views

What causes quadratic hash problem?

I read ScriptSig content during signature (quadratic hashing) discussing quadratic hash problem. Quadratic hash problem is the issue that signing (or verifying) transaction time grows with the square ...
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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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383 views

Any source for a visualized SHA-2?

Is there any source that visualizes how SHA-2 works (including internals) with animated video or an interactive web page?
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2answers
56 views

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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2answers
209 views

API for multiple blockchains

Is there an API to get data for multiple blockchains? Most blockchain explorers already offer an API but I'd like to be able to get information for different blockchains through the same API.
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1answer
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How do I double SHA-256 the header of block #59,500?

I'm not sure how to combine all of this information. https://blockchain.info/block/00000000096af43105123c499521e1d131d172e7e1bf2ed0843290a921f1f6a7 Version 1 Time Bits 470771548 (is this the right ...
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1answer
62 views

Three different HEX having same wallet address how possible?

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

API for getting the Hash-of-thing-to-sign

Does anyone have, or have access to a simple API that can calculate the hashofthingtosign for old transactions along the blockchain? I'm just looking for something simple to see what the "...
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3answers
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ECDSA Signature and the “z” value

The following link contains details on how to reverse the ECDSA signature if given two identical "R" values. http://www.nilsschneider.net/2013/01/28/recovering-bitcoin-private-keys.html I have read ...
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1answer
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Can't find correct z1 & z2 for transaction

I've been trying to understand the issue and repeat Willem Hengeveld's answer, but I think I'm failing at getting correct script for hash. I'm looking for this transaction, my scripts are: ...
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1answer
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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
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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
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About performing SHA-256 hashing on the public key

I am following this link, trying to perform SHA-256 on a given public key. However, I cannot get the expected result. I am using the sha256 library in python hashlib The input is ...
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1answer
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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
884 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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Bitcoin Core ZMQ “hashTx”

Bitcoin Core ZMQ messaging system has hashtx along with 4 other topics. But nowhere it is documented whether the transactions that comes from hashtx are confirmed transactions which are added in a ...

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