What is Hashing with Keccak256 in Solidity?
Overview
A cryptographic hash function is an algorithm that accepts any amount of data and outputs a fixed size enciphered text. The tiniest alteration in the data causes an entire shift in the output.
What is Keccak256?
keccak256 is used to process the Keccak-256 hash of the data input and can be used for the following:
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To create a deterministic, one-of-a-kind ID from a set of data.
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Commit-reveal scheme
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Cryptographic signature with a small size (by signing the hash instead of a larger input)
Example
// pragma versionpragma solidity ^0.5.12;// Creating a contractcontract fellowCoders{uint hashDigits = 8;// Equivalent to 10^8 = 8uint hashModulus = 10 ** hashDigits;// Function to generate the hash valuefunction _generateRandom(string memory _str)public view returns (uint){uint random =uint(keccak256(abi.encodePacked(_str)));// Returning the generated hash valuereturn random % hashModulus;}}
Explanation
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Line 5: We create a
contract. -
Line 11: We are using a 6 digit hash. So, we store
10^6, which is used to extract the first 6 digits. -
Line 14: We create a function to generate the hash value.
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Lines 17: We pack the string into bytes and apply the hash function. Next, we typecast it into uint.
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In line 21 We return the generated hash value.
