A hash is a mathematically reproducible but irreversible process which takes one value as an input and predictably produces a derived value as an output. Hashing is central to Bitcoin mining as well as the generation of Bitcoin addresses.

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Will Crypto Currency End in Next Few Years? [on hold]

We all know how crypto currency works. It's just a hashing algorithm with a key pair. And public key has a chance of collision (of course very rare chance but still lets consider there is a chance for ...
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60 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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84 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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81 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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What is the format that a Bitcoin header is hashed? [duplicate]

Straight from the Wiki: "the hashcash algorithm repeatedly hashes the block header while incrementing the counter & extraNonce fields. " How does it hash the block header? Is the block header in a ...
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79 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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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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24 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: ...
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161 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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40 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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25 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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37 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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47 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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401 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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41 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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60 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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127 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 ...
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157 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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68 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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81 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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26 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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46 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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227 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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47 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 ...
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356 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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246 views

Two identical R value finding z value from two transaction

tx1 from the trans1 i got Input Scripts 30450220262e481b6d8905b5adba67aff05eb8261501b0a9434c0b7f043d00cf8d23c91b022100bf82c0d212f30d3a0599e9b879516d762eaf5688ab83787cf470e99af5a6917101 ...
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226 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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110 views

bitcoin two identical R

Blockchain transaction id 30440220d47ce4c025c35ec440bc81d99834a624875161a26bf56ef7fdc0f5d52f843ad1022044e1ff2dfd8102cf7a47c21d5c9fd5701610d04953c6836596b4fe9dd2f53e3e01 ...
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73 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 ...
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138 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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119 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, ...
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343 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 ...
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135 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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66 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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271 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, ...
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80 views

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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111 views

Given a block, is there a list of all hashes for all possible 2^32 nonce values?

I am working in a computational research lab, and we're taking a look at Bitcoin. I'm trying to develop a simulation of Bitcoin mining for a nonexistent computer architecture. I want to simulate the ...
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151 views

Are Bitcoin ASICs Optimized for Fixed Length Messages?

Bitcoin block headers are 80 bytes. int32_t nVersion; // 4 bytes uint256 hashPrevBlock; // 32 bytes uint256 hashMerkleRoot; // 32 bytes uint32_t nTime; // 4 bytes uint32_t nBits; ...
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203 views

How safe is bitcoin with regard to a random address generation attack? [duplicate]

Imagine an attacker implementing something like the following pseudocode on the fastest ASIC farm money can buy: attack(blockchain, my_address) addresses = ...
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249 views

two people with same PUBLIC address, how will people/network know how to deliver bitcoin

I understand that a bitcoin address is a combination or more than one kind of encryption and entropy, and I also understand how improbable it is that the same address will get generated at the same ...
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371 views

How can I mine ALT SHA-256 coins using a Bitmain S4?

The bitmain S4 does 2TH/s out of the box with no overclocking. For many alt SHA-256 coins, this can be 10% - 50% of the entire network hashing power, which would allow us to gain alt coins quickly, ...
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199 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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48 views

How do satoshidice's draws work? (HMAC hashes) [duplicate]

I am trying to understand how does a satoshidice draw work. As far as i have understood satoshidice generates daily two public hashes: HMAC hash (H from here on) Position hash (P grom here on) ...
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3answers
577 views

Random numbers using blockchain

How are the block hashes generated? Are they trully 100% random (generated by hardware) or is it pseudo-random (generated by software)? Can i rely on it or any other blockchain data to make a 100% ...
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1answer
91 views

Laymans guess to determine how many hashes must be computed to you find a specific value

I have a question about bitcoin, lets say that the output is uniformly random and that it is 256 bits in length. The output of the hash function y=H(t) begins with 25 zeros - how many times would one ...
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2answers
531 views

Is it possible to convert Bitcoin Miner to Litecoin Miner?

I have 90Gh/s Bitcoin Miner and its almost useless for Bitcoin Mining with current difficulty. By changing the Linux software installed in it can I convert this Bitcoin Miner to Litecoin Miner? I am ...
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873 views

What does it mean for a cryptocurrency to be ASIC-resistant?

I guess the question I'm asking here is what does it take for an altcoin to be ASIC-resistant? What does it need to have?
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120 views

How to get bitcoin address from the pubkey_hash using bitcoin-abe or something else?

I'm using: https://github.com/bitcoin-abe/bitcoin-abe to import the blockchain into a mysql DB it is almost done after 5 days. So I started looking at the data and didn't see any addresses. I know the ...
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116 views

Create custom Transaction ID using Bitcoind raw transaction

I would like to know if it's possible for someone to create a raw transaction using bitcoind or bitcoinJ and predict the Transaction hash.How exactly is the transaction ID(hash) calculated ?
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102 views

How is hash rate of mining hardware calculated

The mining hardware does a double sha-256 hash of the header while mining. Is each sha-256 operation counted when determining the hash rate or is the whole sha256(sha256(header)) counted as one hash? ...