Questions tagged [keccak]

keccak is a cryptographic family which is used in ethereum and nowerdays provides the standards for sha-3

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What is the significance of the function keccak256(abi.encode(to, ids))

I have seen a Solidity smart contract made by Polkamon, which is used to store NFT hashes, so that users can create an NFT without minting it, so that they can save Gas fees if they don't like their ...
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When is hashing used when creating a smart contract?

I was going through the solidity docs and in a contract example given I have seen keccak256 used. // Perform checks to determine if transferring a token to the // `OwnedToken` contract should proceed ...
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1answer
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Solidity's keccak256 hash doesn't match WEB3 keccak hash

TL;DR: I have a method in a contract to calculate a keccak256 hash, and I'm trying to replicate it in Web3, but the hashes don't match. My problem is very similar to the one in this question, but the ...
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1answer
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How to Keccak 256 hash in front end JavaScript before passing it to my smart contract

I would like to build a simple JavaScript (JS) front end that checks if a field submitted is the pre-image of a keccak256 hash I already know in my smart contract. I currently use the following: ...
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Python and Solidity keccak256 function gives different results

I am working on implementing a smart contract application in which, on and off chain calculations will exist. I will have to calculate the Hash Function of multiple integers with Python and Solidity. ...
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How to store in `address` two kinds of addresses at once?

I have a set of address values, each of them can contain a real Ethereum account (user account or contract) or a "virtual" address (an address pseudo-randomly generated by my contract, in ...
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1answer
158 views

How can i `ecrecover` in solidity to verify the digest produced by `web3.utils.soliditySha3` in JS side?

Javascript side: id = 128 uri = "xxx://xxx" hash = web3.utils.soliditySha3(id,uri) sign = web3.eth.accounts.sign(hash1, privateKey) Solidity side: function(uint256 id, string memory uri,bytes v, ...
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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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eip-1967 address calculation

I have read EIP-1967 and i have study how work proxy contracts. There is something i do not understand in EIP-1967. Here is what i have understood: Logic contract's storage variables are stored in ...
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Constructing a Merkle tree of objects

I can keccak strings to construct the leaves of a Merkle tree, for example, ['a', 'b', 'c']. But what's the recommended approach to constructing objects instead of merely 'a'? Let's say: { address:...
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C# how to compute Keccak256 to match Solidity?

I have a simple Solidity function as below: function testKeccak(uint8[] buffer) public pure returns (bytes32) { return keccak256(abi.encodePacked(buffer)); } Testing the keccak256 hash using ...
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How can I generate hash of string received from function argument

I want to generate hash of string received through function argument. Sha256 require bytes in argument. How can I convert and then save hash in _hash variable. struct ORGANIZATION{ bytes32 hash; ...
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How does the Keccak256 hash function work?

As the Ethereum platform relies on the Keccak256 hash algorithm, I'd like to get a better understanding of it. My rough understanding is something like this: a function accepting a finite set of bits ...
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How do I Encrypt Transaction Input Data Encode ABI

I'm buying erc20 token how can I encrypt my transaction input data . I using Javascript WEB3.JS method Can you help me with this? like this when try on check etherscan. Warning: Unable to decode input ...
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1answer
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Cross-posted from Stack-Overflow: Using Google Cloud Key Management Service to sign an Ethereum transaction

Cross-posted from question I've been working on writing a signer service for an Ethereum transaction manager and I need to sign Ethereum transactions using Google KMS Golang APIs. I'll try and ...
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Problem with sha3.keccak_256() update method in Python

I made a simple SHA3 Python script to generate Ethereum addresses and priv/pub keys. After that I sent some ETH to those addresses but then found out that priv keys do not correspond to the addresses ...
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1answer
222 views

How to sign and verify data with ethereumjs-utils?

In my contract I'm verifying if some data was correctly signed by the owner. It looks like this: require( owner() == ecrecover(keccak256(abi.encodePacked(this, aCustomId)), v, r, s), ...
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1answer
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How to get the non-packed solidityKeccak hash in Python Web3

For Web3.solidityKeccak(['bool'], [True]) , Python Web3 yields: 0x5fe7f977e71dba2ea1a68e21057beebb9be2ac30c6410aa38d4f3fbe41dcffd2 This matches the output of keccak256(abi.encodePacked(true)) in ...
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1answer
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Incorrect result for hash calculation

According to this link, [https://github.com/ethereum/EIPs/blob/master/EIPS/eip-155.md][1]. The "signing data" becomes: ...
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1answer
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How to implement owner check in Solidity

Is there any EIP that specifies how to implement function in contract, that let's you call any other function as contract owner, with provided signature? I don't want to reinvent wheel. For example: I ...
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What is the computing power of the Ethereum network in FLOPS?

The aproximate computing power of current Bitcoin network in terms of FLOPS (FP32) has been estimated at about ~80,000 exaFLOPS and being aware of the limits of the analogy because of the widespread ...
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How to call the super contract function where msg.sender should be same in solidity?

I am trying to call contract A.fun_A() via Contract C contract A{ function fun_A(address tenant, uint itemId){ //Here the msg.sender should be msg.sender in C require(msg.sender == ...
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1answer
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How to get data location for string > 31 length

The documentation says: bytes and string are encoded identically. For byte arrays that store data which is 32 or more bytes long, the main slot stores length * 2 + 1 and the data is stored as usual ...
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Passing a hash value to function

I'm trying to authenticate users by comparing the hashes created by backend server and contract. Seems like "byte32" values cannot be coerced into strings. So, instead I'm converting it into ...
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1answer
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Why is there a SHA256 pre-compiled contract when SHA256 is also an opcode?

The question is in the title :). Trying to understand why there is both an opcode and pre-compiled contract for SHA256. To execute the computation, would people canonically "CALL" into the pre-...
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1answer
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keccak256 output is different on ruby vs javascript…?

Ruby ethereum libraries use: https://github.com/phusion/digest-sha3-ruby require 'digest/sha3' '0x' + Digest::SHA3.new(256).hexdigest('0x0') => "...
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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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converting keccak from old version: pragma solidity 0.4.19; [duplicate]

I am trying to compile following code: pragma solidity 0.5.9; contract test{ //https://github.com/ethereum/solidity/issues/3469 address payable owner; mapping (address => bool) pd; uint public sS;...
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keccak3 in SOLIDITY and in WEB3 different hashes for an address type field

How can I get the same resulting hash from Keccak-256 ()in solidity and web3.sha3() in web3? IN solidity using keccak256( address ) and using web3.sha3 ( address ) gives different results. In web3 ...
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1answer
223 views

Running Solidity's keccak256 in python

I want to run Soliditykeccak256(abi.encodePacked(challenge_number, msg.sender, nonce)) where nonce is uint256, challenge_digest is bytes32, challenge_number bytes32, testTarget is uint. What's the ...
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Solidity keccak behavior

I have a weird issue. I'm trying to keccak256 packed encoded arguments in Rust [which should mimic Soldity's behavior to be checked on chain later]. I've failed for now. To figure out the issue I've ...
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How to compare two bytes32?

I was using strings before I read that using bytes is gas cheaper. Now I changed my strings to bytes32 but I don't know how to compare them. I need to check if two bytes32 are equal in the require ...
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1answer
50 views

Unable to store hash in blockchain [closed]

I have a major problem/ I've got a simple smart contract that stores data (a text in blockchain and it works well, but when I pass keccak256, it stores only the string passed in as an argument but not ...
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1answer
430 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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1answer
156 views

Generating an address from a public key in C++

Example: Input key = 0x025f37d20e5b18909361e0ead7ed17c69b417bee70746c9e9c2bcb1394d921d4ae Output address = 0xd09D3103CcABfb769eDc3e9B01500Ca7241D470A I have been using an algorithm from keccak-tiny....
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1answer
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Solidity. Concatenate and hash two strings

Hi all I need tho sha256 two strings. I am new to solidity. This is what I've got: function addressToString(address _addr) public pure returns(string memory) { bytes32 value = bytes32(uint256(...
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How to keccak256 multiple types in web3js to match Solidity keccak256?

if I keccak256(string1, address1) in Solidity, and then use web3.sha3(string1, address1) in web3.js, I get different results, even though when I do both with only string1 as a single argument, they ...
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1answer
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Different outputs for Keccak256(), which one is right?

To get a value from contract storage I used this geth code succesfully: var contractAddress = '0x88e726de6cbadc47159c6ccd4f7868ae7a037730' var index = '...
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1answer
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How are we able to send 512 bit hash as a bytes32 variable?

I have a code that is working: solidity function checkSignature(bytes32 h, uint8 v, bytes32 r, bytes32 s) public pure returns (address signer) { bytes memory prefix = "\x19Ethereum Signed ...
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Is there a way to obtain the same Hash using Keccak256 from Web3 and ZoKrates hash function such as sha256packed?

I am trying to use the hash obtained from keccak256 (applied to a number or input) and using it into sha256packet from ZoKrates (or other function) for comparing it with the Hash obtained in Zokrates ...
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563 views

How to generate the full list of function selectors for a contract?

A contract has many functions and how to automatically generate the full selector list, including inherited functions, for the whole contract? Preferred solution shouldn’t require more than a web ...
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1answer
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Why solidity's keccak returns different value from online generators?

I try to implement my own little modifited commit&reveal voting. I have problem with revael phase. Reveal metod signature look like: function reveal(bytes32[] memory _reveals, bytes32[] memory ...
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Which cryptographic hash function does Ethereum use?

Many sources refer to the use of the "SHA3" cryptographic hash function within Ethereum, but the Ethereum project began before the SHA3 standard was finalised, and there was some confusion/controversy ...
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What is topics[0] in Event logs?

Here's a snapshot from etherscan.io
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1answer
134 views

What is the best way to store a hexadecimal value in an array in Solidity?

I am attempting to store a hash (web3.sha3) into an array in a smart contract. What is the best way to do that?
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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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exploiting keccak for random number generation?

Whenever a ticket will be purchased, a random number will be generated function _mightWin() internal { address _player = msg.sender; // players address uint256 ...
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1answer
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How to get EVENT name from event signature hash?

I fount that some developers can get event_signature_hash for a event's name MyEvent(uint256) by using bellow code: event_signature_hash = w3.sha3(text='MyEvent(uint256)').hex() But vice versa, I ...
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1answer
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Is pre 0.5.0 keccak256(a,b) equivalent to post 0.5.0 keccak256(abi.encodePacked(a,b))?

In pre 0.5.0 Solidity if you wanted to hash a some set of data you would do keccak(a, b, c). Post 0.5.0 keccak only takes 1 arg and it is suggested to use keccak(abi.encodePacked(a,b,c)) instead But ...
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1answer
276 views

Where is string stored in solidity storage?

I'm trying to check where is stored a string in storage in Solidity. For testing this I'm using this code: pragma solidity 0.5.4; contract AssemblyString { string s; // slot 0 function set(...