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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919 views

API Authentication via Python

I'm having trouble following LakeBTC's API instructions for connecting to their API via Python. API Documentation: https://www.lakebtc.com/s/api I have my key (email address) and secret. I'm using ...
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1answer
412 views

Why are blocks hashed?

Am I correct that addresses are hashed to compress a huge text-represented coprime into something of manageable size? Am I also correct that transactions are hashed for the same reason and also ...
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242 views

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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457 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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1answer
588 views

How does Bitcoin verifies signature if addresses are one way hashed

I'm stuck at understanding Bitcoin's transactions. So, the owner must sign the transaction with his private key, then miners can verify whether this signature matches his public key. However the ...
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2answers
11k views

When mining with 2 computers, do I need to use 2 separate wallets addresses?

I understand that each miner is working on a different block. Correct me if I'm wrong but this is because the first transaction in a block basically contains my wallet address so I can receive the ...
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4answers
4k views

Alternative Cloud Hashing sites to Cex.io [closed]

I am really impressed with Cex.io and their whole concept of trading Ghs for Bitcoin as well as cloud mining which I find to be novel and interesting. Are there any other sites like that? I know ...
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1answer
68 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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1answer
177 views

Why do miners need a nonce if the timestamp changes the hash of the block?

As the title says. If the timestamp is constantly changing with every guess, why does the miner also include the nonce? Is it because they're mining too fast for the timestamp to change?
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127 views

How do more leading zeroes make it more difficult to find a block?

A couple of articles describing the process of mining do say that the more miners are in the network, the more 0 numbers are included in the encoded hash of the particular block. I cannot find an ...
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1answer
28 views

Doubt regarding hashing function in Merkle trees

From what I read, say in a block, there are 4 transactions. The hash value of transactions A and B are combined together to get the hash AB. Same goes for transactions C and D to get hash CD. Later AB ...
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1answer
271 views

How specific are ASIC's design? Can they single hash SHA256?

I understand that Bitcoin's ASICs are a highly optimized piece of equipment and, therefore, are also very specific. My question: are they able to do a single (or triple?) SHA-256 hash at all? And, ...
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3answers
632 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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8k 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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780 views

Hash pointers: Are hashes of data used as addresses?

I am wondering how hash pointers are implemented in reality. Currently, I am reading this article about hash pointers. According to this website a hash pointer allows both to request data and to ...
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1answer
358 views

How are thousands of transactions put into a block?

As much as I hate to admit it, I am not very tech savvy, and as such, I am fairly confused about the concept of the blockchain. I understand that the chain holds information about previously approved ...
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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
2k views

Two identical R value finding z value from two transaction

tx1 from the trans1 i got Input Scripts 30450220262e481b6d8905b5adba67aff05eb8261501b0a9434c0b7f043d00cf8d23c91b022100bf82c0d212f30d3a0599e9b879516d762eaf5688ab83787cf470e99af5a6917101 ...
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2answers
466 views

Difficulty for hash (reversed function of “does hash met difficulty/target”)

What is an algorithm to determine what maximum difficulty already found hash meets?
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490 views

Required number of bits in nonce [duplicate]

Is there a formal proof that with N bits to iterate in the nonce of the block, a hash satisfying proof of work will be ever found? How large that N (number of bits in the nonce) should be to satisfy ...
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1answer
22k views

How to work out my hardware's hashrate power

Using my existing hardware, I want to work out which altcoin is still profitable to mine. I have found this link: http://dustcoin.com/mining But don't know which values to enter into the boxes at ...
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4k views

How to hash data from 'getblocktemplate' request

I've been reading lots of articles, trying to understand how to hash the data returned from getwork; but I totally overlooked getblocktemplate. I'm just trying to understand how all the data below is ...
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1answer
18 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
201 views

where in the source code is the the proof of work checking the blockheader hash and nonce?

Where in the source code do we check whether hash(blockheader*nonce) < Difficulty In fact, the line I found is as follows: https://github.com/bitcoin/bitcoin/blob/v0.17.0.1/src/pow.cpp#L87 My ...
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1answer
158 views

How to determine right address from address hash

I'm using private libbitcoin server and libbitcoin explorer. When I use bx fetxh-transaction, it returns something like: I'm trying to figure out, how to get right address from address_hash. When I ...
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1answer
1k 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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1answer
926 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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1answer
140 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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1k views

How are Bitcoin Signed Messages generated?

Ledger Nano S and other pieces of Bitcoin software and hardware can sign messages using the private key associated with an address. Doing this, I get the following output: -----BEGIN BITCOIN SIGNED ...
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2answers
121 views

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
121 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
290 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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125 views

What dead simple algoritm can be used for generating checksums by pen and pencil?

I'm holding a course on Bitcoin and blockchain technology. On my agenda I have an exercise where I'm going to let the attendees create their own blockchain on the wall using post-its. I'm in search ...
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1answer
229 views

Why do we inverse the hash of the blockheader?

Let's pick this example blockheader-hashing in Python: from hashlib import sha256 import hashlib header = "...
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2answers
1k views

Two addresses with same hash160?

It seems that two addresses have same hash160 69665e2c4fac771e340f8c6f91c719b0c37a6a8f: here 0 BTC: https://blockchain.info/address/1AcJanbHGrBFwS3KJMDW8kEZMtHiJhatzE here 0.00720407 BTC: https://...
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1answer
4k views

Where is debug.log file in Bitcoin source code?

I am running 64bit Ubuntu 17.04, I am following this tutorial for creating a new altcoin. I am up to section 7, here to be exact: The first time you run the compiled code (daemon or qt), it will say "...
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1answer
1k views

Why do we need block hashes in blockchain?

I believe there are around 3 types of overall hashes that we deal with in Bitcoin. block hashes Merkle tree hashes (makes transactions tamper proof by hashing them up to the Merkle root) public-...
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1answer
795 views

How to generate random addresses from public key such that they're recoverable later using pub key only

I head that from a public key, you can generate random addresses just by adding a nonce to the public key. Then, you can regenerate all these addresses again when you need, right? If my wallet has ...
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1answer
3k views

same R value is used for two different addresses? finding z1 and z2 value and privatekey

txid1 txid2 input script 1 304502206bcc247f1259262b4035bfa84f0397a69f69baa01659daaf94fe1164b650c86a022100a044b38e8264a1c928ddd28b4657aa7109d1ea30e911208c7ce57abcb1451fe601 ...
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1answer
542 views

How does Multi-Signature Pay 2 Script Hash (P2SH) enable stronger security?

Coinfloor says it will pay out withdrawals using Multi-Signature Pay 2 Script Hash. What is Multi-Signature Pay 2 Script Hash? I read What is "Script Hash" address exactly and how does it ...
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1answer
554 views

Are transactions still tamper-proof if blocks are hashed without nonces?

If an alt were to forgo difficulty and timed release of new supply by removing the nonce from blocks therefore the whole difficulty/target system, is hashing without nonces still providing the same ...
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1answer
292 views

How is the solution hash in a block generated?

For example, in the Genesis block in Bitcoin, from which values was the solution hash "000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f" derived from? I understand that the nonce is ...
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1answer
43 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
61 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 ...
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1answer
23 views

College Economics Student in Support of Crypto Looking for Live Hashrate Data

I am a college economics student doing a Thesis project in support of the long term viability of Crypto. Does anyone know where I can get live Hashrate data for free or for sale? I appreciate it - ...
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1answer
58 views

What will happen when a collision in SHA256 be found?

Would the protocol migrate to another Hash Algorithm inmediatly? What would be the next? SHA3 or BLAKE 2?
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1answer
156 views

How many bits of entropy is a Bitcoin address?

I've seen references to 160 bits of entropy, but I'm not sure if this is universal or just applies to the old address format.
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1answer
47 views

What would be the effect on the number of leading zeros hash generation if bitcoin increase its nonce size from 32 to 60 or 100 bits?

If Bitcoin increases its nonce size from 32 bits to double or triple the size, how will it affect the speed of getting the right hash with the required number of zeros?
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1answer
42 views

How to transfer hash power from one pool to another

Is it possible to transfer hash power from one pool to another? If yes, how?
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1answer
329 views

How many hash calculation is needed to reach one BTC?

What I am asking for is a formula and it's source of numbers to put in there and calculate how many hashes must be calculated to get 1 bitcoin today(or every other day in future)? For example, if I ...

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