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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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, ...
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2answers
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What is preventing me from simply constructing a hash that's lower than the current target?

I just started learning about Bitcoin, and something I can figure out is why miners have to use a random process (hashing a nonce) to get lower than the target. For example, if the target is ...
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3answers
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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 ...
6
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2answers
702 views

How do pool operators do their hashing?

For every "getwork" served by the pool, a Merkle root must be calculated for a block. The run time of SHA-256 is proportional to the number of "chunks" of 256 bits, and a typical block will have ...
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3answers
119k views

How many hashes create one Bitcoin?

Irrespective of the length of time required to calculate one hash, how many hash operations are required to produce one Bitcoin?
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3answers
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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. ...
5
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3answers
7k views

Where can I see an input that will hash to a solution?

So as my understanding goes, there's some input (block header) that needs to be altered (via a nonce or other mechanism) which is run through a SHA256 to generate an output with X amount of leading 0'...
5
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1answer
588 views

Why do two miners get different hashes for the same list of transactions?

According to the Bitcoin Wiki: it is extremely unlikely for two people to have the same Merkle root because the first transaction in your block is a generation "sent" to one of your unique ...
5
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2answers
7k views

How do signatures work?

Just curious, if I send a transaction from one address to another, how do they verify it without knowing my private key?
5
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1answer
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In Getwork, how does one calculate the value of Hash1?

(I know the hash1 and midstate are eventually going to be deprecated, but I'm a little curious about them) In Getwork there is a field hash1. From a sample call to bitcoind I received its value as: '...
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1answer
668 views

How do I generate the Bitcoin Cash hash preimage?

I am attempting to manually generate a signed transaction which is to be sent from my address 1GiJZtN7wjUuL4V5i7ZYYDAvFtqi5AhCDr which is bitcoincash:qzk9nxh6qpd9yt3hvv6vvun78s834f3escdhu2vdjp in the ...
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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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2answers
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Why was the RIPEMD-160 hash algorithms chosen before SHA-1?

Bitcoin uses both SHA-256 and RIPEMD-160 hashes. Most often a double-round SHA-256 is used, but for address generating, RIPEMD-160 is used because it generates a shorter hash value. RIPEMD-160 has a ...
5
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1answer
240 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 ...
5
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1answer
472 views

bitcoins can use different algorithm, how and implications

I read that if sha-256 was compromised at some point in the future, or for any other reason, bitcoin could switch to a different algorithm can someone detail how exactly that would work, and what the ...
5
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1answer
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Why do transaction/blockchain based gambling sites use such complicated methods for proving fairness?

Doesn't the block hash or the transaction id provide enough entropy (for example, by using block_hash % 37 to generate a random number between 0 and 36)? Block Chain Roulette determines the lucky ...
4
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1answer
317 views

A security need for Bitcoin to fork to quantum resistant algorithm in a few years?

in just a few years I believe that quantums will exist that break asymmetric ciphers, and bitcoin is based on asymmetric ones like public-key-cryptography, correct? Symmetric algorithms are supposed ...
4
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3answers
605 views

Which is the smallest hash that has ever been hashed?

Let's assume, the hash 00000000000000000024c0bdbec66a889778c00bc69be0a96cbbd98b75c3ce09 of block #499644 is smaller than 0000000000000000002d429f39afec70c938e888c3417d690bbc85e83529991c of block #...
4
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1answer
446 views

Duplicated hash values in mining reward

This transaction is contained in two MainChain-Blocks: https://blockchain.info/tx/e3bf3d07d4b0375638d5f1db5255fe07ba2c4cb067cd81b84ee974b6585fb468 On Blockexplorer there is a note of this anomaly: ...
4
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2answers
300 views

What is the variable in a block that holds hash of found PoW?

Can anyone please tell me, which variable holds the hash of the solution of block's PoW in broadcasted block? I know that a block consists of (I am pretty sure I am forgetting some variables here): ...
4
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1answer
163 views

Is the idea of a “honey hole” such as in gold mining, present in bitcoin mining?

I understand the output of the SHA-256 hashing function is a random number between 0 and 2^256. Does the randomness of this output imply that there cannot be a, so to say, honey hole in the hashing. ...
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3answers
642 views

Future-proofing a deflationary currency from future counterfeiting

Say someone locks away a wallet in durable storage for 100 years and BitCoins are still actively used. Are those BitCoins still going to be valid if they haven't been traded in/upgraded to the newer ...
4
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2answers
523 views

What would happen if two public keys had the same Base58 hash?

If two different public keys had the same Base 58 hash, what would happen? Could one key spend money in the other account? What would happen to the monies received by the shared base58 hash?
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1answer
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Why the leading zeros in the desired hash pattern?

Why are leading zeros desired in the block chain hash? I have searched the internet but cannot find why.
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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 ...
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 ...
4
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1answer
28k views

What is a megahash and how is it used to estimate the rate at which bitcoins are mined?

What part of the bitcoin network requires hashes and why? What is the relation between money and the megahashes a card can do?
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1answer
406 views

How does a share help in the discovery of a new block?

https://en.bitcoin.it/wiki/Pooled_mining: A share is awarded by the mining pool to the clients who present a valid proof of work of the same type as the proof of work that is used for creating blocks,...
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1answer
2k views

What is the hash-rate of the Bitcoin network that results in the maximum difficulty?

According to https://en.bitcoin.it/wiki/Target the target is a 256-bit number. As the total hash-rate of the Bitcoin network rises, this number decreases to increase the difficulty. How much hash-rate ...
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2answers
12k views

What is the relationship between hash rate and accepted shares?

Specifically this question is about Litecoin, but I suspect the answer would apply to both. Say you have a rig mining at 700Kh/s (LTC). It seems that you get, more or less, a one or a few accepted ...
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2answers
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What determines SHA256 performance on different types of hardware?

I know the answers to many questions on here briefly touch on this point, but I'd like to get a consolidated answer that really touches on the key differences between different types of hardware which ...
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1answer
3k views

bitcoind getmininginfo says hashespersec is 0

I started mining yesterday on a low-end system, trying to figure out how it works. I used the bincoind build from Debian. When I try bitcoind getmininginfo today, I get the following output. { "...
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2answers
2k views

Mining Block header bit reversing

While trying to understand the mining process and checking in python..... i am puzzled with which info from/to pool are in Little Endian, which one needs reversing in building the block header + ...
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3answers
1k views

What other purposes can I use my [obsolete] hashing hardware for?

It's pretty easy to reuse CPUs or Video cards that were previously used for Bitcoin hashing, but what can I do with FPGA hardware when the difficulty becomes too high for it to be worthwhile to mine? ...
4
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1answer
381 views

bitcoin two identical R

Blockchain transaction id 30440220d47ce4c025c35ec440bc81d99834a624875161a26bf56ef7fdc0f5d52f843ad1022044e1ff2dfd8102cf7a47c21d5c9fd5701610d04953c6836596b4fe9dd2f53e3e01 ...
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2answers
94 views

Is that proved that for each block there is always nonce value which will make block hash to start by n count of 0

Sorry for the obvious question, but I'm looking for a mathematical prove. Block header is calculated as a concatenation of the following values. Version hashPrevBlock hashMerkleRoot timeStamp Bits ...
4
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1answer
505 views

A full/multi nonce range search or just a partial range search?

In a work, there are only two elements in the block header change between hash attempts. That is, NTime and Nonce. The miner starts the nonce search to get a valid share, and there are several ...
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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 ...
3
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2answers
509 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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2answers
4k views

Why is difficulty measured in a hash’s leading zeroes?

I understand how generating a SHA-256 hash containing any specified sequence requires lots of guessing and checking. The longer the specified sequence, the more rarely that it will appear. And I ...
3
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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. ...
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 ...
3
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3answers
2k 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% ...
3
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1answer
2k views

Longest unconfirmed transaction?

I recently tried to make a transaction with coinbase. In a hurry I put no fee though. It's still unconfirmed and blockchain.info doesn't recognize my hash. But my btc qt wallet is debited. My question ...
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2answers
1k views

Checksum vs. Hash: Differences and Similarities ?

What are similarities and differences between a "checksum" algorithm and a "hash" function? Can they be used instead of each other? Or their usage are different? For example, for verifying the ...
3
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2answers
5k views

Given the probability of finding a block, and time taken, can I infer hashrate?

I'm trying to externally calculate the hashrate of a given miner based only on an arbitrarily defined target that I assign, then calculate probability it will be found. Once this probability is ...
3
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1answer
898 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 ...
3
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2answers
818 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 ...
3
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1answer
2k views

What values are hashed in the SHA-256 algorithm, and what would be the next iteration until a possible header is found?

I've been doing a lot of reading on mining and software related to mining but I can't quite get my head wrapped around the specific nature of what is being hashed together. So far I feel like the ...
3
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1answer
482 views

Is there a guaranteed hash for every block? [duplicate]

Possible Duplicate: Nonce size - Will it always be big enough? My question may be misphrased, if so, I'll correct it if you let me know in the comments. My understanding of mining is that the ...

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