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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180 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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0answers
12 views

save document hash in blockchain [duplicate]

I need to save hash of pdf into blockchain. I have hash of my pdf, but I don't really understand if it's possible to enter this hash in blockchain without financial transaction? Is it possible to ...
0
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1answer
24 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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0answers
40 views

Where do I find a comprehensive list of all bitcoin hash creators?

For a research project I am looking for a comprehensive list of bitcoin hash creators. How can I access this information? Any help is greatly appreciated.
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1answer
46 views

How many Hashes are in a single Terrahash [duplicate]

Im looking at getting an ASIC that runs about 1 Th/s and im wondering how many hashes is equal to a terrahash?
3
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1answer
44 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" ...
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2answers
88 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
100 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
85 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 ...
4
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2answers
161 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
101 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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0answers
7 views

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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1answer
178 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
55 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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1answer
141 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&...
2
votes
1answer
191 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
118 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
40 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
43 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
59 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
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2answers
837 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
48 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
66 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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1answer
264 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
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1answer
173 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
76 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
86 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
27 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
70 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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1answer
296 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
51 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
457 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
286 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
275 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
122 views

bitcoin two identical R

Blockchain transaction id 30440220d47ce4c025c35ec440bc81d99834a624875161a26bf56ef7fdc0f5d52f843ad1022044e1ff2dfd8102cf7a47c21d5c9fd5701610d04953c6836596b4fe9dd2f53e3e01 ...
6
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1answer
105 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
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2answers
149 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
140 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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1answer
402 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
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2answers
166 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
67 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
292 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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0answers
102 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, ...
1
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1answer
140 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 ...
5
votes
2answers
156 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; ...
3
votes
2answers
219 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 = generate_tree_of_all_nonempty_addresses(...
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3answers
274 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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0answers
397 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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2answers
215 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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0answers
49 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) ...