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daniel weber
daniel weber

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What is Hashing in Solidity?

A cryptographic hash function is an algorithm that takes an arbitrary amount of data as input and produces the enciphered text of fixed size. Even a slight change in the input gives a completely different output.

Solidity provides the following cryptographic functions:
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Ethereum uses Keccak for hashing which is similar but not the same as SHA_256. For proof of work, it uses a custom scheme called ethash which is designed to be ASIC-resistant.

Example: In the below example, a smart contract is created to take a string as input and give an 8 digit hash as an output.

// pragma version
pragma solidity ^0.6.6; 

// Creating a contract
contract helloGeeks 
    // We want hash to be of 8 digits 
    // hence we store 10^8 which is 
    // used to extract first 8 digits 
    // later by Modulus 
    uint hashDigits = 8;

    // Equivalent to 10^8 = 8
    uint hashModulus = 10 ** hashDigits; 

    // Function to generate the hash value
    function _generateRandom(string memory _str) 
        public view returns (uint) 
        // "packing" the string into bytes and 
        // then applying the hash function. 
        // This is then typecasted into uint.
        uint random = 

        // Returning the generated hash value 
        return random % hashModulus;

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