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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 ...

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Why is the nonce bruteforced from 0 to n while mining?

bitcoin noob here. I was wondering why is the nonce increased from 0 to n while searching for a blockhash? Why not start at some other integer > 0 for example? My background is in ethereum-dev, so ...
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Input transaction hashes not matching transaction hashes

I parsed blockchain .dat files. I wanted to find transaction input address for a given transaction input. For this I looked at "prev hashes" from inputs, reversed the byte order in them and then ...
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20 views

Can't we change the block data instead of a nonce?

In the process of solving a hash puzzle, isn't it possible to change the transaction data instead of changing a nonce?
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23 views

Natural Language Processing and Blockchain?

This question is about one of the applications of the Blockchain in Artificial Intelligence. I am not very familiar with Natural Language Processing and I see that there is a Blockchain platform ...
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1answer
24 views

Getting transaction id from raw transaction of a multisig address

I am able to get the tx id (or transaction hash) of almost any transaction but the one where the script starts with an "OP_O" (which is, I think, the null dummy introduced here https://github.com/...
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45 views

Estimated number of hashes

This is not a duplicate of previous, similar questions I've read on StackExchange, since none of those questions, nor the answers, go into the difficulty theory, as espoused on the Bitcoin Wiki. ...
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Checksum vs. Hash: Differences and Similarities ?

What are similarities and differences between a "checksum" algorithm and a "hash" function? Can they be used instead of each other? Or their usage are different? For example, for verifying the ...
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retrieving an original data from a hash: is it reliable?

Normally, one of the purposes of hashing a string (such as a transaction) is summarizing the data to save the size because of the space limitation. If this proposition is true, now assume we need to ...
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18 views

How to protect the latest block in block chain be tampered?

We know for each block in block chain, it has the previous block header hash which make the block be tampered become difficult. If the block is tampered, then all blocks after this tampered block need ...
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28 views

How come Merkle tree is more efficient when tree branches are not stored in blockchain?

Suppose we have 8 transactions in a block X as follows and we know every node's hash value of the whole Merkle tree (that is, including intermediary nodes such as 45). Then if someone claims ...
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81 views

General private/public key generation

Not sure if this is the correct forum to ask, but I couldn't find a general one for all cryptocurrencies I wanted to get an idea on how the whole cold-storage private/public key generation works for ...
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21 views

Can Bitcoin Tech be Used to Protect Journalists [closed]

Over eight Nigerian journalists are currently in police detention because they published investigative news stories that didn't sit well with the government of the day. How can the bitcoin ...
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28 views

Have all hashes of unlocked difficulty levels of cryptocurrencies been mined?

I'm wondering if all the hashes of a previously unlocked difficulty level of a cryptocurrency, such as 0000000000000000xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx BTC , have been completely ...
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“tx” array inside blocks contains transactions hashes?

When I use the "getblock " command on my bitcoin core client, it returns, beside other things, an array called "tx" with hundreds of hashes. Are these the individual transactions hashes or something ...
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What are the hashes in Unspent outputs?

I am a newbie to Bitcoin. Looking at curl https://blockchain.info/unspent?active=1Cdid9KFAaatwczBwBttQcwXYCpvK8h7FK I guess that the script is the owner's address.I am not sure about this. "...
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3answers
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When a node receives a transaction, what steps does it do to verify that transaction?

I know that it verifies the block hash by calculating each hash of the contiguous blocks in order, but does it verify the balance of each wallet sending the transactions as well? And does it do the ...
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64 views

Mining Theory: What would happen if a block hash collision occured? [duplicate]

To my knowledge, neither SHA256 or scrypt have ever had provable instances of hash collisions occur.. However, if this highly unlikely event was to happen, what would that mean for the state of the ...
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160 views

Why A Block have a Merkle root hash? [duplicate]

That is the question, why a block needs to have a Merkle root hash, as Iundestand, once a block is mined the hash value of this block is stored at the header of the next one so, it generates the chain....
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I want to know how I can express a phenomenon found in Merkle Trees mathematically

I want to know how I can express a phenomenon found in Merkle Trees mathematically. If I want to figure out which leaf node in a Merkle Tree has changed I can look at the authentication path to figure ...
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77 views

What does this comment in Chainparams.cpp mean?

There is a comment in the Bitcoin source code under src/chainparams.cpp /** * Build the genesis block. Note that the output of its generation * transaction cannot be spent since it did not ...
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1answer
100 views

Unable to validate a signed message from Ledger

Using Ledger Nano S you can sign a message, either through the UI (which is a Google Chrome app) or through Javascript by calling Ledger.signMessage as specified here. Using this, I get the following ...
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55 views

How would you find the Merkle Root with a Block that contains 6 transactions?

Let's use block #100205 https://www.blockchain.com/en/btc/block/0000000000033d0de6f4ebe93b3b142424cdbecf4bd98b948e856c4a55f09f76 This block contains 6 transactions. After the second level of hashing ...
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30 views

Why Does an Online SHA Generator not work for Double Hashing data? [duplicate]

Let's say you use: https://passwordsgenerator.net/sha256-hash-generator/ You plug in data and it produces the first hashed value. If you plug that output in for the second SHA256 it outputs the wrong ...
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How nodes verify if the hash on a P2SH output is from a valid script?

I understand how the validation works if someone wants to spend coins from a multisig address. But what if the receiver makes a mistake and provides an invalid script hash to the sender? Is there ...
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1answer
27 views

What is the exact input for the hash function?

I've read that it's some variation of: version, previous block hash, merkle root, time, bits, and nonce, but I'm not certain on where to get this data and how it should be formatted. I'd like to know ...
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1answer
196 views

How do I concatenate two hashes in Python?

Concatenating and double SHA-256 hashing "a751efbeabe73bdf9d08df5760104feff915d9d807d4c62178cdeb98d8c25f43" with itself "a751efbeabe73bdf9d08df5760104feff915d9d807d4c62178cdeb98d8c25f43" should ...
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74 views

I'm trying to hash transactions together to find the Merkle Root!

Transaction #59500 has 045c670f1c02c919 as its coinbase. Transaction 1 is 6653ad77d695752cff9fe63bbb5702a53807be534c537251d53de06aac5ca093. Transaction 2 is ...
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1answer
59 views

Why use Merkle Root (and not just concatonation of all hashes?) [duplicate]

I am studying the bitcoin protocol and do not exactly understand why a Merkle root is used to register all the transactions. What is the point of using a tree-wise structure when you can also just ...
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1answer
49 views

Why is the target truncated?

Reading the docs on target: The maximum target used by SHA256 mining devices is: 0x00000000FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF Because Bitcoin stores the target as a ...
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1answer
90 views

HASH160 to address - What am I doing wrong?

I am running this code and nothing happens. I am trying to hash160 a script with OP_HASH160 {scriptHash} OP_EQUAL and get a P2SH address as output but not sure this is the right script to achieve ...
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1answer
66 views

Why is it important that the hash algorithm is puzzle friendly?

I don't understand "PUZZLE FRIENDLY". Here the definition I read: A hash function h is puzzle friendly if for every possible N-bit output value y, if K is chosen from a distribution with high ...
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51 views

What does a bitcoin transaction contain?

I'm learning about basic transactions and know that a transaction should contain: i) Signature of the sender using some operator: sign(private key,message) ii) Receivers Public key (wallet address) ...
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1answer
86 views

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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39 views

Can I get the same stats as are on blockchain.info and btc.com by running a full node?

There seem to be some discrepancies between blockchain.info and btc.com, specifically I am looking to extract the following info: "Relayed By", there was a block that was listed as unknown on ...
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1answer
108 views

Confused About Hash In Satoshi Nakamoto Diagram

In Satoshi Nakamoto's diagram: Consider the Hash block in the first transaction block above: How is that Hash value calculated? I see arrows from an Owner's Public Key and another arrow, so it's ...
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Where is the Coin in the Transaction Hash Chain?

In Satoshi Nakamoto's diagram: I see a Hash in each transaction block. It would be interesting to see the first block in the chain--it isn't shown. I say that because I do not see anything that ...
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1answer
63 views

Is the bitcoin blockchain really non-corruptible? [duplicate]

Some people say that proof of work is better than proof of stake, because it's not possible to rewrite the whole blockchain on-spot. One would need to "re-mine" everything. But I think this is not ...
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154 views

Bitcoin API(s) - how to pair (or obtain) BOTH sender and receiver addresses with a transaction ID (hash)

Various block explorers exist, which offer REST APIs. So far been using blockchain.info and btc.com Here is what we have: - List of bitcoin addresses Here is what can easily be got with that info: -...
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36 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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79 views

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
55 views

Would mining future bitcoins break the bitcoin?

assuming an bitcoin miner with very much hashrate like bitmain would decide to mine "future" bitcoin blocks and provide them within very short time to the network, would this break the bitcoin? As i ...
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1answer
53 views

Extract output address from raw script in bitcoin protocol

I'm working on bitcoin protocol and exactly i want to extract raw script from output script to gain address from tx messages. for common scripts, like scripts start with 0x76(means OP_DUP), we can ...
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1answer
83 views

Bitcoin RIPEMD160 purpose

Bitcoin uses RIPEMD160 on top of SHA256. Is its sole purpose to make public key address shorter or does it strengthen security in any way?
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120 views

What is Bitcoin's “genesis hash”?

From Lightning Network documentation: Used in several of the BOLT documents to denote the genesis hash of a target blockchain. This allows nodes to create and reference channels on several ...
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3answers
158 views

Getting the wrong txid for coinbase transactions

I'm trying to hash transactions to get the txid. I get the hex values from blockchain.info. I get the correct hash for all transactions except for the coinbase when I hash it twice. Is there something ...
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1answer
656 views

Bitcoin mining difficulty and hash rate

On blockchain.info there is the charts that shows the mining difficulty over time and the hash rate over time. See: Hash: https://blockchain.info/nl/charts/hash-rate Mining difficulty: https://www....
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How two transactions with the same hash can cause double-spending

Let's consider following situation: Vendor owns address X. Adversary sends transaction T1 to X with hash Y and receives product from vendor. Adversary sends transaction T2 to address which he owns ...
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225 views

Why is it impossible to modify a transaction in the blockchain?

Many pages (including Wikipedia) say that it is impossible to modify a transaction which is already in the blockchain included. But why is it so difficult?
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90 views

Is pre-image attack useful for mining?

I know that SHA256d is strong enough and it's not likely that will be broken soon but let's say someone knows how to find pre-image. The adversary chooses random hash starting with n zeroes (less than ...