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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 output. Hashing is central to Bitcoin mining as well as the generation of Bitcoin addresses.

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1answer
5k views

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 ...
3
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3answers
208 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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3answers
986 views

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.) ...
0
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1answer
166 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 ...
1
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1answer
172 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 ...
1
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1answer
9k 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 ...
1
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1answer
189 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
364 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
511 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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0answers
107 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?...
2
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1answer
981 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 <&...
0
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1answer
622 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 ...
3
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4answers
5k 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 ...
3
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1answer
923 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 ...
6
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1answer
4k views

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" ...
9
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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 ...
2
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1answer
622 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: ...
0
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1answer
187 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 ...
9
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2answers
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
348 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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2answers
323 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
3k views

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&...
3
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1answer
849 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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1answer
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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1answer
145 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?
2
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1answer
98 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
190 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? ...
6
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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 ...
1
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1answer
275 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 ...
3
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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 ...
2
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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 ...
2
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1answer
709 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 ...
2
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1answer
206 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 ...
3
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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 ...
2
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0answers
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) ...
2
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1answer
373 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?
3
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1answer
3k views

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
568 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*>(...
2
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1answer
2k views

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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1answer
1k views

Two identical R value finding z value from two transaction

tx1 from the trans1 i got Input Scripts 30450220262e481b6d8905b5adba67aff05eb8261501b0a9434c0b7f043d00cf8d23c91b022100bf82c0d212f30d3a0599e9b879516d762eaf5688ab83787cf470e99af5a6917101 ...
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1answer
2k views

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

txid1 txid2 input script 1 304502206bcc247f1259262b4035bfa84f0397a69f69baa01659daaf94fe1164b650c86a022100a044b38e8264a1c928ddd28b4657aa7109d1ea30e911208c7ce57abcb1451fe601 ...
4
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1answer
342 views

bitcoin two identical R

Blockchain transaction id 30440220d47ce4c025c35ec440bc81d99834a624875161a26bf56ef7fdc0f5d52f843ad1022044e1ff2dfd8102cf7a47c21d5c9fd5701610d04953c6836596b4fe9dd2f53e3e01 ...
7
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1answer
521 views

Is Quark as secure as SHA 256?

I'm trying to make certain I'm understanding the purpose behind the Quark algorithm. There are lots of devices that need secure algorithms but have severe power and processing constraints such as ...
5
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3answers
1k views

Visualize Bitcoin Hashing

According to https://en.bitcoin.it/wiki/Hash, BitCoin uses the SHA-256 hash algorithm to generate verifiably "random" numbers in a way that requires a predictable amount of CPU effort. ...
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2answers
2k views

Work distribution in a mining pool

How is work distributed among members of a pool? Regarding the block hashing algorithm and valid hashes of a new node, how is the set of solutions for nonces "distributed" among miners?Is a nonce, ...
3
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1answer
2k views

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 ...
4
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2answers
1k views

What is a midstate? How does using a midstate speed up hashing?

This defines "midstate" as the "precomputed hash state after hashing the first half of the data." I've heard "midstate" used in the context of speeding up hashing. How does using a midstate speed up ...
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2answers
416 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?
6
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3answers
1k views

Does every nonce really have an equal chance of winning?

I set out to test the claim: "Every nonce has an equal chance of winning." Time Evolution So, I plotted, with gnuplot, the nonce values vs. hashes for all the valid blocks in the blockchain:(Also, ...