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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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

finding a fast way to calculate a nonce

I found a way for ultra-fast nonce calculation, based on my own method. Does it makes sense to introduce such method, or the complex way of nonce calculation has some advantages? Thanks!
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537 views

More than one valid hash block

Discovering a new block is a task about generation of millions of hashes in order to find one valid hash, which is a hash less than the current target. The question is: Are there more than 1 valid ...
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1answer
217 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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0answers
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What's a good repo to fork if you want to create a blockchain like a “Math” coin or Curecoin. (mining equations, not hashes)

I want to create my own crypto currency and I want to know what's the best github repo to fork when it comes to making a blockchain that's based off of getting the miners to do mathematical ...
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1answer
2k views

How to calculate the BIP34Hash?

I know this going to be a repeat question, however I am still puzzled with the implementation of the BIP34 especially where it come to its hash. Referring to the chainparams.cpp at github : https://...
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1answer
2k views

Why does the hash-rate change so drastically?

I've been watching the global estimated hash-rate, as estimated by blockchain.info. While it is clearly increasing, it also varies around 20% day-to-day. Yesterday, it was around 4,325,000 TH/s. ...
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1answer
298 views

When mining, does one also include Merkle root data into block header when testing for hashes?

I am just a beginner trying to understand technical details of bitcoin. As far as I know, the Merkle root of a block works to provide summarizing hash of list of transactions. And according to my ...
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1answer
4k views

How long does it take to perform a single SHA256?

I'm not talking about hashes/s, but specifically, the amount of time required to perform a single SHA256 on the fastest computers known. How long does a very fast ASIC take to perform one SHA2? Is ...
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1answer
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Blockchain SHA256 hash and nonce [duplicate]

I have been reading the SHA256 hash creation with a random nonce. So, my understanding is every miner would pull uncommited transactions and would try to create a Hash of the transactions with a ...
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3answers
219 views

What can be changed in signed bitcoin transaction?

What can be changed in signed bitcoin transaction? I mean how is possible to modify transaction to change its hash, but keep transaction valid, without need to have sign private keys?
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Generating differnet addresses from same public key?

There's a gap in my understanding regarding the generation, via hashing, of bitcoin addresses. (I'm quoting from Antonoplous below for convenience, but I have consulted multiple other sources.) ...
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1answer
169 views

Thin Client and OP_RETURN

I'd like to better understand how a light client works. As far as I know, a light client stores locally only the block headers (80 bytes each) and it receives a new block header on average each 10 ...
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1answer
175 views

Do HTLC transactions work today or do they need a new soft-fork?

I thought that HTLCs was just a kind of a script construct that would allow to unlock funds for a period of time, which can be unlocked to anyone that provides the original string that matches the ...
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1answer
10k views

How bitcoin addresses are generated?

what's up? Fact: a Bitcoin wallet can handle multiple private keys. In ECC, you can have 2^256 private keys and, for each key, you can have 2^256 public keys. Assuming that's right (please correct ...
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1answer
194 views

Does 4 byte Nonce enough to proof of work?

Is it always possible to find an hash value of a block, smaller than the current difficulty, just using 4 byte (Nonce) ? How can we be sure about it ?
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2answers
396 views

Is there any chance to check the name by bitcoin hash?

Someone recently wants to sell me an iPhone, but the seller does not want to show me anything about it. It's a second-hand phone, and I'm worried about it a little bit. Is there any chance to see the ...
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1answer
524 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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111 views

What's the most fair mining algorithm

lots of people claim that Bitcoin's mining algorithm is unfair because ASIC has definite advantages over other chips. So, what can be the most fair algorithms that maximizes decentralization of mining?...
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1answer
1k views

How is the extra nonce formatted?

I'm trying to understand how a block is put together. From here, I know that the extra nonce used to be in the format: pblock->vtx[0].vin[0].scriptSig = CScript() << pblock->nTime <&...
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1answer
625 views

Bitcoin Mining Computational Power [duplicate]

1/ I do not understand why bitcoin mining is random when hashing is deterministic. reference : https://en.bitcoin.it/wiki/Nonce Can the mining pool with the most mining power always win? What value ...
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4answers
6k views

If SHA256 produces an alphanumeric hash, how can a hash be “less than a certain value”?

I was under the impression that Bitcoin's method for validating a hash involved making sure the hash started with a pre-determined number of zeroes. However, after reading the docs here, I see the ...
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1answer
984 views

Verifying a bitcoin trx on the Unix cmd line with OpenSSL?

I want to use openssl on unixoide systems to verify a transaction. I step on errors, when trying to verify a bitcoin trx’s hash. Here I am working on Mac OSX and OpenSSL (1.0.2a 19 Mar 2015). I know ...
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1answer
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How is a block header hash compared to the target (bits)?

I'm trying to wrap my head around the mining process by doing a small example of block hashing. According to the Wiki entry about difficulty, the target for a block hash can be read from the "bits" ...
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4answers
10k views

hash versus hash pointer

I am doing coursera online course on Bitcoin and Cryptocurrency Technologies. It defines the concept of hash pointer in the first lecture as pointer to where some information is store and ...
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1answer
669 views

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
190 views

Bitcoin adresses seem not to be collision resistant. Please tell me I am wrong [duplicate]

I am trying to understand Bitcoin addresses, but it does not seem to be easy at all. As far as I know, a Transaction uses one or more addresses as input and one or more addresses as output. Is this ...
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3k views

Where did the idea of blockchain come from? Git was already using it since 2005

With bitcoin's blockchain, each block's hash is computed with the previous block's hash. That makes all blocks an immutable chain. This is not the first time people used a hash-chain. As far as I ...
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3answers
366 views

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
2k views

Why is the hashrate getting so high?

The Bitcoin hash rate is MASSIVE right now. What exactly causes the hashrate to increase?
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332 views

How was 59 days determined with 1 TH/sec from “Mastering Bitcoin”

In Mastering Bitcoin in the section on Difficulty Bits Andreas notes: This means that a valid block for height 277,316 is one that has a block header hash that is less than the target. In binary ...
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2answers
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Generating Bitcoin Public and Private Keys

I managed to write the below code which will create public and private keys Private Key $input = "satoshinakamoto"; $sha256 = hash("sha256", ($input)); echo "<strong>Private Key: </strong&...
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1answer
870 views

Why change the nonce instead of just rehashing?

Why do miners increase the nonce to compute a block hash rather than just generating a random block hash? It seems to me that both approaches would have the same likeliness of finding a result that ...
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2k views

Does Bytecoin use SHA-256?

Also, doesn't this mean that I can use hardware such as a bitcoin usb block erupter to mine it?
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147 views

Hash-based crypto-currencies?

What are the most famous crypto-currencies which use repeated hashes as proof-of-work? What are the other proof-of-work methods?
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1answer
99 views

Whats the public key required for in a transaction?

In figure 1 of the original paper by satoshi, why include the public key of the next owner in the hash?
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1answer
192 views

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
9k views

What is the approach to calculate an Ethereum address from a 256 bit private key?

For a given private key generated by MyEtherWallet, I would like to see I have the tools to independently arrive at similar results. Wrote a wrapper around Keccak to accept both hexadecimal and ...
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1answer
278 views

Question about getblocktemplate

I'm having trouble understanding getblocktemplate. From https://en.bitcoin.it/wiki/Getblocktemplate, I see how to build the block header and then begin hashing by incrementing the nonce, the same as ...
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2answers
81 views

Is it computationally feasible to find two transaction IDs with the same first 20 bytes?

Transaction hashes uses sha256, so they are 32 bytes long. If I have to store a very large database of transaction hashes, only for the purpose of checking existence later on, is it really necessary ...
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4answers
2k views

What exactly is the input for the Hash pointer in block k+1?

I'm not sure how to ask this question clearly so I will ask it three different ways and hopefully someone understands me. Is the input for the hash pointer in block k+1 just the transactions in block ...
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1answer
727 views

Why was finding a hash beginning with a certain number of zeroes chosen as the proof of work?

It seems to me that the reason the proof-of-work involves finding a hash beginning with a (temporarily) fixed number of zeroes is because one can easily check whether they have solved the problem by ...
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1answer
209 views

Why is this transaction stuck?

https://blockexplorer.com/tx/286fefb79f1b0a14526997e8c7bcb4bd7a5665c953586f6bbcd09e441b192d3f this is my transaction blockchain hash This is first time I've actually seen something like this - the ...
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1answer
216 views

In Proof-of-Stake, can a block creator fudge the block hash?

In Proof-of-Work, a block hash is costly to manipulate (say, wanting the hash to be even, or have the hash of the hash smaller than some number) since there is a lot of computing power put into ...
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60 views

Mining , hash and Nonce [duplicate]

I lack something in my understanding of how the mining process works. If a miner has to loop over a block and re-calculate it's SHA256 for only 2^32 (the amount of different nonce values possible) ...
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1answer
389 views

Where is the spec of HashCash so that I can implement it in Java from scratch?

I would like to implement HashCash in an efficient/fast/garbage-free way. Is there a spec to do so? How can someone go by implementing HashCash from scratch?
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Compute TxID of Bitcoin Transaction

Originally posted to StackOverflow but with no response. Thought I might have better luck here. I've successfully created a Bitcoin transaction in C# according to the protocol specifications. Here's ...
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1answer
572 views

Shabal256 code explanation

Can anyone please explain the code below with comments? What are pbegin & pend ? What is ( I believe it is data, where it comes from ?): (pbegin == pend ? pblank : static_cast<const void*>(...
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1answer
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bitcoin address to Hash 160 public key : not consistantly reversible?

When I use blockchain.info tools or bitcointoolkit.info tools to convert an address, such as 1MCNpVGDY7BGjJyWZL5FJZiaVkQEiuxy8H to a hash 160 public key : I get ...
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Two identical R value finding z value from two transaction

tx1 from the trans1 i got Input Scripts 30450220262e481b6d8905b5adba67aff05eb8261501b0a9434c0b7f043d00cf8d23c91b022100bf82c0d212f30d3a0599e9b879516d762eaf5688ab83787cf470e99af5a6917101 ...

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