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.

learn more… | top users | synonyms (1)

3
votes
1answer
28 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?
2
votes
1answer
32 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? ...
2
votes
2answers
102 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 ...
2
votes
1answer
30 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
votes
2answers
51 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 ...
3
votes
4answers
72 views

What is the precise nonce finding protocol?

There are many descriptions of what mining is, but none of them describe it exactly. From what I gather: Mining means finding a nonce c such that for some information s the hash value h(s||c) ...
1
vote
1answer
40 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 ...
2
votes
1answer
133 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
votes
1answer
58 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
votes
1answer
72 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
votes
0answers
23 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
votes
1answer
34 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?
1
vote
1answer
147 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 ...
1
vote
1answer
44 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 ...
1
vote
1answer
4k views

how do I figure out the hash rate of my computer? [duplicate]

My computer has AMD A4-5300 APU W/ Radeon(tm)HD subscore 6.2 Graphics AMD Radeon HD 7480D 4.7 If any one can help , thank you!
1
vote
1answer
268 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 ...
0
votes
1answer
185 views

Two identical R value finding z value from two transaction

tx1 from the trans1 i got Input Scripts 30450220262e481b6d8905b5adba67aff05eb8261501b0a9434c0b7f043d00cf8d23c91b022100bf82c0d212f30d3a0599e9b879516d762eaf5688ab83787cf470e99af5a6917101 ...
0
votes
1answer
179 views

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

txid1 txid2 input script 1 304502206bcc247f1259262b4035bfa84f0397a69f69baa01659daaf94fe1164b650c86a022100a044b38e8264a1c928ddd28b4657aa7109d1ea30e911208c7ce57abcb1451fe601 ...
4
votes
1answer
103 views

bitcoin two identical R

Blockchain transaction id 30440220d47ce4c025c35ec440bc81d99834a624875161a26bf56ef7fdc0f5d52f843ad1022044e1ff2dfd8102cf7a47c21d5c9fd5701610d04953c6836596b4fe9dd2f53e3e01 ...
4
votes
0answers
65 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 ...
4
votes
2answers
127 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. ...
3
votes
2answers
103 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, ...
1
vote
1answer
289 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 ...
3
votes
2answers
108 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 ...
1
vote
2answers
61 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?
5
votes
2answers
257 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, ...
5
votes
1answer
782 views

What mining performance can we roughly expect from the Intel SHA extensions of the upcoming Skylake processor architecture?

Intel is scheduled to release their new x86 SkyLake microarchitecture in Q3 2015. Among other interesting features, it will introduce SHA extensions that will allow hardware acceleration of the Secure ...
1
vote
0answers
66 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, ...
5
votes
2answers
146 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; ...
4
votes
3answers
526 views

How do cloud hashing companies profit? (leasing hashing power)

I think I'm missing something. There are a bunch of cloud hashing companies that lease hashing power. Let's take cointellect for example. They have contracts from 10 days to 24 months. If I buy a 10 ...
3
votes
2answers
195 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 = ...
1
vote
3answers
244 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 ...
1
vote
0answers
337 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, ...
1
vote
2answers
172 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 ...
1
vote
0answers
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) ...
3
votes
3answers
484 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% ...
2
votes
2answers
673 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?
1
vote
0answers
115 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 ...
0
votes
1answer
106 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 ?
3
votes
1answer
46 views

Proof of work - does the equipment matter?

It technically doesn’t matter whether I am using a super computer or a laptop to do the proof of work, it’s simply that with a super computer I can go through the attempts much faster, which means I ...
0
votes
1answer
57 views

Miners produced/ing duplicated hash values

This transaction is contained in two MainChain-Blocks: https://blockchain.info/tx/e3bf3d07d4b0375638d5f1db5255fe07ba2c4cb067cd81b84ee974b6585fb468 On Blockexplorer there is a note of this anomaly: ...
3
votes
3answers
2k views

ECDSA Signature and the “z” value

The following link contains details on how to reverse the ECDSA signature if given two identical "R" values. http://www.nilsschneider.net/2013/01/28/recovering-bitcoin-private-keys.html I have read ...
2
votes
1answer
139 views

Namecoin - How to Find Block Height via Block Hash?

Is it possible to use namecoind to determine the block number from a block hash? Going from height to hash is easy: namecoind getblockhash But going from hash to height appears to be impossible... ...
1
vote
0answers
59 views

How to monitor hash rate over time to diagnose issues

Running a Scrypt mining rig using GPUs. Want to know if there's a way to monitor your hash rate over time. Pool stats arent that reliable from what I understand. CG Watcher, does a decent job, but ...
3
votes
2answers
127 views

SHA256 * 2 on header - what am I doing wrong?

I've been experimenting with the php code here: https://en.bitcoin.it/wiki/Block_hashing_algorithm (after correcting the small bug of $x=; to $x=""; ) With these blocks 0 and 125552 (for example) it ...
1
vote
1answer
296 views

How does a proof of work limit of `~uint256(0) >> 20` translate into a difficulty of `1 / 2^12`?

In the Litecoin source it is written: static CBigNum bnProofOfWorkLimit(~uint256(0) >> 20); // Litecoin: starting difficulty is 1 / 2^12 How does that compute? ~uint256(0) >> 20 is ...
3
votes
2answers
124 views

Are Bitcoin Block Hashes Predictable

to create the block chain, the Bitcoin network runs hashing algorithms for each block, is it mathematically possible to predict the hash value of say, the 100th block from the last block currently in ...
2
votes
2answers
133 views

What is the average number of hashes it takes to mine bitcoins?

I'm just curious about this. I'm not sure if the length of zeros in the hash result is directly proportional to the probability, or how to calculate this.
2
votes
0answers
20 views

mining pcie 16x and 1x together caused rejects

I have 5 msi radeon R9 290 cards and this board https://www.asus.com/Motherboards/Z87PLUS/specifications/ . With 3 pcie 16x everything runs smooth but, as soon as I add the first 1x into the equation, ...
1
vote
1answer
93 views

Why does the hash come before the signature?

The first figure in the original paper of Satoshi is a diagram of transactions. This diagram seems to indicate that the transaction data is hashed before the sender's signature is appended. Why not ...