Questions tagged [sha256]

A 256-bit variant of Secure Hash Algorithm 2

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What does SHA256 hast must be lower than current target?

I'd like to ask if someone can help explain this definition found on https://en.bitcoin.it/wiki/Target "The SHA-256 hash of a block's header must be lower than or equal to the current target for ...
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What needs to be changed in Bitcoin if SHA-256 is broken? [duplicate]

I come up with a little bit "catastrophical“ question. I declare that I understand the degree of improbability of such a scenario in our lifetime, but I would still be interested in your opinion. ...
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Why is *double* SHA-256 hashing used in the block header? [duplicate]

Both the previous block's header hash and Merkle root hash use double SHA-256 hashing. Why are two rounds used?
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How does the bitcoin network difficulty syntax work?

So, essentially what my question is what does the "syntax" of a bdiff (bitcoin target difficulty) look like? I know that its a number, i.e the current network difficulty is set at around ...
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What is the actual working implementation code used in double hashing a block header in c++?

I need to successfully generate a hash value based on what i feel so far has been described as a hexadecimal filtered sha256 implementation... or something like that. I've been here , here , here, ...
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Proper way to get sha256 hash in c++ using openssl?

Given the following variables: unsigned char text [] = "Test String"; unsigned int len = strlen ((const char*) text); unsigned char hash [SHA256_DIGEST_LENGTH]; Is there any reason to do ...
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BitCoin SHA256 - ShortCut

just a general question, would it be ethical to start mining bitcoin using a shortcut, in the SHA256 hash (if that may even be possible), and mining at a much much faster speed using very less ...
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How do i create/implement a midstate function (One that can accurately calculate the midstate of already mined blocks)

I'm creating an AI controlled bitcoin miner but I'm having trouble manually & locally creating a midstate function to be used for optimizing the mining process. Basically I've created independent ...
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What time of encryption from late 2000s contains house, smileyface, squares, letters and numbers?

Have a encrypted password or key typed to paper, i vaguely remember doing it, not sure if note pad was involved or some site , i remeber something about sha-2 , and sha- 256, and why i should use one ...
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can i diy an asic miner?

Iam interested in mining bitcoin so Iam wondering if I can get a pcb for hashing and bring asic chip that algorithms are sha-256 and stick them together with some other electronics and have a control ...
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checksum = SHA256(SHA256(prefix+data)) - why double hashing?

From 'Mastering bitcoin' - checksum = SHA256(SHA256(prefix+data)) The 'data' is, for example, an address, which was calculated using SHA256 and then RIPEMD160. Why do we need double hashing when ...
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How many SHA256 hashes can a single thread compute?

ASICs use many threads to compute SHA256 hash functions in parallel. At the time of this post, Antminer S19 can compute 110TH/s. How many SHA256 hash functions per thread can the best SHA256 ASIC ...
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Can we benefit from Collatz conjecture-based proof of work?

Can we benefit from Collatz conjecture proof of work to enhance bitcoin utility? F Bocart 2018:"Inflation Propensity of Collatz Orbits: A New Proof-of-Work for Blockchain Application" argues ...
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Can we have multiple possible nonce making same number of leading zeroes in the hash?

Is it possible to have different nonce which are satisfying the same condition of having let's say 4 leading zeroes in the hash? Is it possible that one node suggests 89123 nonce and other node ...
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Why does the TXID have 256 bits when Bitcoin's address security is 160-bit?

Commonly used Bitcoin addresses have the security of 2160 (due to the RIPEMD-160 hash). This means that Bitcoin is based on the fact that 160-bit security is good enough. If someone breaks 160-bit ...
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Is there a list of processes within Bitcoin that use hash functions?

Hashing within Bitcoin is done in several different areas of the code. EG: We have the SHA-256 mining algorithm, the Merkle tree hashing, and I believe double hashing within certain areas (SHA-256D). ...
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For a block containing 'x' number of unverified transactions, how many SHA256d hashes are performed to obtain the hashmerkleroot?

I've been trying to understand this for a few days now. I understand that the hashmerkleroot is the root node of a fully perfect binary tree. I also understand that the sha256d hashes would be the non-...
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As a developer, what steps do I need to take to generate private-public keys?

When developing (I'm using Apple Swift), what steps are needed in order to independently create my own pair of private-public keys (with the ability to restore a private key from a mnemonic phrase)? ...
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Determination of Block Size Limit

In Bitcoin Mining, there is a limit on the size of any block added to the chain. What happens if, for instance, a block's nonce is so large that the block's size exceeds the limit? Secondary questions:...
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How to pad Bitcoin Header in the SHA Algorithm Passes?

For any bitcoin block we combine various Header fields to create a string which is an input to a 2 pass SHA algorithm. The resultant hash must match with the Hash in the Block header for the Block to ...
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Already mined block hash showing zeros at the end when I hash it in online sha256 two times

Hi I tried hashing a already mined block with this block header ...
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sha256 implementation

Hi I'm trying to use bitcoind's vectorized SHA256 implementation in src/crytpo/sha256_*.cpp in my project. On a first try feeding a block of 64 null bytes to SHA256D64 I obtain the hash {0xe2, 0xf6, ...
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Can a blockchain have duplicate block hashes?

I am writing an indexer that will work with various blockchains and not just Bitcoin. I am wondering if it is safe to assume that block hashes will be unique for a given blockchain, across reorgs. Is ...
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Merkle tree hash - Computing hash manually doesnt match the one computed by SHA256D64

I am trying to go through the code to check the merkle tree hash computation done by BlockMerkleRoot in bitcoin core. The hash computed using online tools by appending transaction hashes is different ...
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Translate c++ function into python: sha256 hash mismatch [closed]

This is not related to bitcoin but it uses most of the bitcoin codebase. I would like to translate some c++ code into python but struggle really hard to get the hashes right. This is the function I ...
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What previously existing technologies made Bitcoin possible?

When watching a tutorial, they mentioned that Bitcoin is based off 4 or 5 technologies that existed for at least a decade before Bitcoin. Satoshi Nakamoto was the first person to combine them all into ...
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What exactly happens to leaves when forming nodes?

If you hash TXIDs with sha256 twice, you get the leaves of the merkle tree. As far as I understand the two outputs of the TXIDs are concatenated / paired. What does that mean? Are they added together?
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Why is the SHA256 regularly applied twice? [duplicate]

I have come across at least two times in bitcoin computations that the sha256 algorithm is applied twice - merkle root computation and address computation. Why is this? Not sure of an appropriate tag -...
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Why is SHA-256 mining secure?

My understanding is the when you are mining bitcoin you are looking for a string, or maybe a binary number (a) such that if you 'add' a to the block (b) you get a number (c) whose hash begins with a ...
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I found a BTC hash. Now what?

I used a mining program written in python and after a lot of time, it found a hash that looks something like this: 0000de957fbfdfc77582e0d0b20c53d2d1d83d8bb8cfe3693521f672bf2a6021 except it has 19 0's ...
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Minimum characters to uniquely identify bitcoin trasanction in blockchain

What is the minimum number of characters (TXID from the beginning) which is generally considered to uniquely identify a bitcoin transaction in the blockchain? (Similarly to git and a commit SHA - ...
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Will a recursive sha256 run over all 2^256 inputs before a collision?

Will a recursive sha256 run over all 2^256 inputs before a collision? Here'a a python program showing my question - will this loop for 2^256 times - given endless memory or will it terminate before - ...
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Lowest numbered Bitcoin hash? [duplicate]

I was thinking about which bitcoin block has the lowest numbered hash. What I mean by a hash as a number is that. For example, the number "1" has a lower hash than "2" in SHA256. ...
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1 answer
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What will happen when a collision in SHA256 be found?

Would the protocol migrate to another Hash Algorithm inmediatly? What would be the next? SHA3 or BLAKE 2?
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9 votes
1 answer
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How many bitcoin transactions can be verified per second on commodity hardware in 2020?

I am trying to figure out how many Bitcoin transactions could be verified per second. Am I correct that signature verification is more expensive than computing Merkletrees and hashes and therefore ...
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download bitcoin core safely: wrong checksum

I've downloaded the "classic" linux bitcoin core 0.19.1 (tgz) on https://bitcoincore.org/en/download/ In the SHA file that's on the website this is the key: ...
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Can you crack SHA-256?

From my understanding, a hash function is an algorithm that takes a unique input and produces a unique output, and a secure hash like SHA-256 cannot be reverse engineered. I saw this thread Won't ...
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1 answer
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How to generate the hash of public key in Bitcoin [closed]

I'm trying to hash the public key with SHA256 and then ripemed160 and get the hash. but it gives the wrong hash Public key: 2b4632d08485ff1df2db55b9dafd23347d1c47a457072a1e87be26896549a8737 Hash ...
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3 votes
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Why can't Grover's algorithm be used for bitcoin mining?

Similar questions have been asked before: Can quantum computing improve Bitcoin mining? Can a Qubit Miner ASIC device be created and what would its impact be on the mining community? However, none ...
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security of the mining algorithms litecoin vs bitcoin - scrypt vs sha256?

how is the cryptanalysis' current state on both sha256 and litecoin's scrypt? is litecoin's scrypt on a security level like sha256? by security i simply mean ways to "break"/"de-cipher" the hash ...
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How does Bitcoin utilize cryptography and secure hash algorithm (SHA) to link records in the blockchain?

I am wondering how Bitcoin uses cryptography and secure hash algorithm such as SHA256 to link the records in the blockchain. And if possible I think it will give me a better understanding if there is ...
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3 votes
1 answer
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Get a correct SHA256 of a PublicKey as bytes

I’m new in code develop and I’m studying it by myself (books, tutorials, official help of sites…) since a year VB.NET. A lot of information I read is in C# that I rewrite in VB.NET. I’ve started four ...
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Merkle Root for Block 100000: calculation in Excel

I am stuck doing the calculations for the infamous block 100000. I am doing those in excel. I am trying to add as much detail here of the operation I am doing and intermediate results. TX1: ...
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Where is the string that generates the hash with 18-20 zeroes?

When bitcoin miners mine, they have to solve a difficult and extremely repetitive math problem using the SHA256 algorithm. The miners are trying (basically playing lottery and almost always working in ...
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5 votes
1 answer
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Is Bitcoin PoW actually SHA256 + Merkle generation? Or have I misunderstood coinbase/append?

Miners can mutate nonce (32 bits) + time (mutates once a second). This allows for 232 (~4 billion) hashes per second. That's not enough anymore for our ASICs as they perform in the TH/s now rather ...
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Generating TXID from transaction's data [duplicate]

As I understand, we can generate a TXID by hashing transaction data through SHA256 twice, and as you know probably, A bitcoin transaction is just a bunch of data that describes the movement of ...
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What's the purpose of CSHA256::Write and CSHA256::Finalize

Looking at Bitcoin Core implementation of SHA256, I noticed it was a bit different from OpenSSL's implementation. In OpenSSL, you would initialize a variable with SHA256_CTX when in Bitcoin Core it's ...
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1 vote
1 answer
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Confused on using SHA256 code from Bitcoin Core

I was looking at Bitcoin Core code to use its SHA256 code but am confused on where I should be looking at. In bitcoin/src/crypto/sha256.h there is CSHA256 and in bitcoin/src/crypto/sha256.cpp there ...
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4 votes
1 answer
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What are the 3 arguments called in function SHA256?

void sha256(struct sha256 *sha, const void *p, size_t size) { struct sha256_ctx ctx; sha256_init(&ctx); sha256_update(&ctx, p, size); sha256_done(&ctx, sha); } I'm trying ...
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Learning + checking the bitcoin address creation process at each step

I’m learning how hashing algorithms are used around the process of bitcoin address creation. I’ve read lots of great examples online that, step by step, show the output of each sequential hashing ...
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