Questions tagged [hash-algorithm]

A hash algorithm is any algorithm that can be used to map data of arbitrary size to data of fixed size. The values returned by a hash function are called hash values, hash codes, hash sums, or simply hashes. In Ethereum, the algorithm used is Keccak 256.

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how to calculate the message part for pedersen hash in solidity

I am trying to implement pedersen hash using solidity. Is it possible to implement and how to split the message according to the conditions of pedersen hash.
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How can I test the placeBet() and settleBet() in ethereum hashdice contracts?

I would like to test the smart contract of hashdice using remix IDE, and using truffle. I wonder how to give the arguments for testing. function placeBet(uint _betMask, uint _modulo, uint _commit, ...
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Why does proof of work targeted zeros always comes at the start of hash? why is it not in the middle or the end of hash?

My question is why always targeted zeros come at the start of hash of the block? I have never seen more than 2 zeros in middle or somewhere else in the hash of mined block... What's the reason?.... ...
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Is it cheaper overall to store a keccak hash or to store a ripemd(keccak) hash?

As titled. I'm learning to build a DApp and I'm wondering if it's worth it to add the extra RIPEMD layer over keccak for a shorter hash to reduce storage costs.
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what is a pseudorandom cache mentioned in ethereum yellow paper

in ethereum yellow paper it says: "There exists a seed which can be computed for each block by scanning through the block headers up until that point. From the seed, one can compute a pseudorandom ...
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128 views

Is any 40 character hex string a valid ethereum address?

I know an ethereum address is generated by getting the last 20 bytes of the keccak-256 hash of the public key, which is 40 hex digits. I also know, an address does not need to have transactions ...
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49 views

Building a deterministic wallet without random seed phrase instead multiple static inputs

If I want to be able to create a private key given inputs x,y,z and these inputs are constant, if I add enough entropy as a salt would it be secure to create a key this way (in terms of brute force ...
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How to verify the sha256 result of integer 5 in the Zokrates tutorial?

The Zokrates tutorial here starts with calculating the SHA256 hash of (the number) 5. The hex representation of the result is shown at the bottom here: However, I could not reproduce this on my ...
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Testing sha256(abi.encodePacked(_argument))

When trying to test a smart contract that uses sha256(abi.encodePacked(_myargument)) I don't get the same hash on truffle ! I tried both web3.utils.keccak256('_myargument') web3.utils.sha3('...
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Need to help in adding bigendian support for Keccak256.cpp

Need help in making the keccakf function based on endiness in https://github.com/ethereum/solidity/blob/develop/libdevcore/Keccak256.cpp. I have gone through similar functionality at https://github....
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Hashnot matching generated from solidity contract and web3js

I want to make hash same as generating by solidity contract from web3 or ether's js. In solidity contract hash generation by below : sha256(abi.encodePacked(no of parameters)). Kindly help for it. ...
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How does a message signed in Remix IDE?

What is signing method that is used in remix IDE and how is the hash value calculated from the message that is being signed?
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563 views

block-header hash verification

As part of a validation service I am working on, I need to be able to verify that the blockHeader hash was created correctly. Based on my understanding following are the steps to regenerate the header ...
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126 views

Match web3py hashing function to solidity hashing function

If I am using web3py to hash some data, like so, msgHash = w3.soliditySha3(['bytes32','bytes32'], [dataBytes, saltBytes]); What would be the correct way to hash inside of a Solidity contract and ...
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193 views

HMAC-x implementation for solidity

Is there any implementation of HMAC-SHA1 or HMAC-SHA256 or any other hashing algorithms for solidity? I found this but it's not working.
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I want to compare hash that I have passed in the argument of the function but keep getting this error

function compare(string memory input, uint _y) public returns (uint){ bytes32 hashedinput = keccak256(input); } Error: Invalid type for argument in function call. Invalid implicit conversion from ...
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Calculating a hash of a set of keys in Solidity

I have the following problem that I'm trying to think of an efficient solution for. Suppose I have a set of unordered keys (KEY_1, KEY_5, KEY_2, KEY_4), and I want to calculate a unique hash for this ...
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Why does a full client need to store the DAG?

The yellow paper says that miners and full clients must store the DAG dataset, but light clients can verify block headers by generating only a few necessary pages from the DAG. It makes sense to me ...
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130 views

Why is this random algorithm not good enough?

Many lotteries on Ethereum use random algorithms to determine a 'winner'. For instance, this function is bad because has some vulnerabilities (read here about some): function random() private view ...
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retrieving an original data from a hash: is it reliable?

Normally, one of the purposes of hashing a string (such as a transaction) is summarizing the data to save the size because of the space limitation. If this proposition is true, now assume we need to ...
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How is the keccak256(a, b) function implemented?

I need to understand how keccak256(a, b) is implemented and how it differs from keccak256(a || b). Is the content padded? I need this because I do not want to allow for vulnerabilities where a user ...
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Common use cases for hashing functions? [closed]

I'm developing my first dapp with solidity and I was wondering in which cases should I use hashing functions like keccak. I know how they work but it is not clear to me when should I use them and to ...
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Hash of address pair combination where order is irrelevant

I have a contract where I often set stuff for a combination of 2 addresses. Because the parameters addressA and addressB are interchangeable I currently save the information redundantly. Example: ...
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752 views

sha256() output

I used sha256() hash of a string and I got the following result 0x0de69f56365c10550d05e65ae8229dd0686f7894a807830daec8caa879731f4d for string Hello World2. Now I want to find out leading byte from the ...
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Hashing Algorithm - Multiple choices in Solidity

Is it possible to choose another SHA algorithm - say SHA256 - in Solidity? Anyone having issues with NIST compliance?
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Error deploying contract to my private network

I keep getting this "Error: The contract code couldn't be stored, please check your gas amount." message when I try to deploy my contract to the blockchain. I read that is a generic error so I'd like ...
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872 views

From golang sha3 to solidity sha3

Trying to match "golang.org/x/crypto/sha3" lib with solidity sha3() is giving me a hard time. Its been discussed in here, but I somehow cant apply it in go. How do I handle a big.Int type s.t i get ...
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Are Ethereum Contracts Vulnerable to Hash Table Poisoning Attacks?

Does anybody know something about this? I know that in general terms we will say not, but looking on the internet I found that isn't sure the answer to the question: Can the EVM’s Internal ...
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463 views

Is a block number unique or does it change if the block becomes uncle? Does the transaction hash include a block hash as input?

Is a block number unique or do I need to save block hash to identify a block? Does transaction hash include a block hash as input?
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309 views

Help with error please (SHA256 returns 0x)

I'm just playing around with testrpc vs creating my own private blockchain and for some reason when I use testrpc and i use SHA256 in my smart contract to return a hash it gives me a proper one. But ...
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361 views

How can I create public-private key for a ERC20 wallet that using user's email address?

I am working on a side project that provides a wallet (Think Coinbase, Binance, etc) like interface to users where they will sign in using username and password. To be able to provide a clearer ...
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129 views

SHA3_512 library, convert the input and output to 512-bit bytes

The SHA3_512 library takes an input uint64[8] and outputs uint32[16]. To convert the input from 64 bytes and the output back to bytes, I wrote this, but it gives the wrong result. What are some ...
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41 views

Smartpools' sha3_512, is there a stand alone implementation?

Smart pool has implemented sha3_512 (contract), tough it looks like it is combined with EthHash. Is there a stand alone library just for the sha3_512 function?
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482 views

sha512 in Solidity or assembly, does it exist? [duplicate]

Is it possible to do sha512 within a smart contract? Or, not?
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995 views

How does Ethash work?

I've looked at the wiki in search of how the information about Ethash algorithm but I did not find the answer. Where can I find detailed information about it or can someone explain it?
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393 views

Keccak hash of null values, result in different hashes for different types

I was testing the hash value of null values for different types and I'm curious how it generates different results for different types. Here are the results. String = ...
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245 views

Hash a message in ethereum-js and check in Solidity

I'm trying to check an hashed message inside my Solidity smart contract. In JavaScript I hash the message as follows: util.sha3(Buffer.concat([ new Buffer(address1), new Buffer(bytes32), new ...
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214 views

How Merkle Tree obtain root node hash (example from 'Understanding the ethereum trie')?

I read Understanding the ethereum trie and try to do examples from that article. Now i am at ex1.py - first exaple. Look at code from that example: import sys sys.path.append('src') import trie, ...
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9k views

Difference between keccak256 and sha3

I have been reviewing keccak256 implementation and sha3-256 that follows the FIPS standard. The sponge function is taking a while to set in, but I have noticed a difference in implementation : I ...
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701 views

What happens on hash collisions for, e.g., transactions, blocks, and contracts?

What happens on hash collisions for, e.g., transactions, blocks, and contracts? What happens if, say, two transactions hash to the same value? In this case, we say that a hash-collision occured. I'...
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Can a mined block have an odd number of transactions? If so, how does the Merkle root in that case?

Merkle Tree pairs transactions and hashes them and the process continues till we get to the root. But how would this pairing process work if the number of transactions were odd?
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Why geth use scrypt for key derivation?

As I understand scrypt was designed to be computationally intensive, so that it takes a relatively long time to compute. For what geth need this? And why it does not use, for example, SHA-256?
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Ethereum Transactions Take So long

It's first time when I tried to make an Ethereum wallet and to make a transfer. Compared to what I am used with other type of d.currency, this transaction seems to be taking forever. In almost 24h ...
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Smart Contract with web3j - Stored SHA hash returned is not the same as input

I have a contract that stores sha-256 hashes of documents (stored as bytes32). I also have a method to retrieve a hash that is mapped to a unique id for the document. However, when I retrieve and ...
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1answer
416 views

What is FNV and FNV function

When I was started to explore the ethash algorithm then I found this- FNV was used to provide a data aggregation function which is (i) non-associative, and (ii) easy to compute. A commutative and ...
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359 views

Mining UBIQ and DBIX using open-ethereum-pool

Open-Ethereum-Pool is configured to mine Ethereum; how do I configure it to mine UBIQ (which uses ethash) and DBIX coins? Thanks for answers
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Is there any project to calculate different hashes like md5, sha1 etc. in solidity?

I'm looking for solditiy-code to generate hashes of different hash-algorithms MD5 SHA1 SHA512 and more. Is there any project which implemented hash-algorithms in solidity? Is there someone out ...
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1answer
3k views

Is Ethereum's mining algorithm vulnerable to ASICBOOST?

Bitcoin's hashing algorithm uses a multi-step hashing function. Some miners have used a technique referred to as ASICBOOST to exploit this. I'm unclear on the specifics, but it has something to do ...
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324 views

Proof of Work validation

I am not too understanding this equation. Do any one know it? Especially what is m stand for since I cannot get it from the paper. Thanks
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Revealing played value

I'm writing a smart contract where participants are asked to submit a value (1 to 1000000) in the submission period, and then reveal what that value is in the revealing period. In order to hide it ...