Storage – Storing SHA-256 64 Byte String in Solidity

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I am wondering what the best way to store a SHA-256 hash is in solidity. The SHA-256 output is a 64 byte hex string when I pass the hash from my web app to my contract. The issue I run into is that I start getting errors such as inaccessible dynamic type when I use strings – since strings are actually just dynamically sized arrays. Any ideas?

Best Answer

I would chop it up into two bytes32 client-side and re-assemble it client-side. The simplest form might be:

bytes32 part1;
bytes32 part2;

This is as economical as it gets, and can be passed around between contracts if needed.

Hope it helps.

p.s. If you don't need to recall them and only need to validate their existence (from some other off-chain source or claim), hashing them into a single bytes32 would provide enough precision and 50% gas reduction.

Related Solutions

Solidity – Error When Using String Type as a Mapping Key

I am proposing using bytesN instead string:

pragma solidity ^0.4.6;
contract C {
    struct User {
         uint balance;
    }
    mapping (bytes24 => User) public accounts;
    function newUser(bytes24 id, uint balance) {
         accounts[id] = User(balance);
    }
}

you could also convert bytes to string look at : How to convert a bytes32 to string

Solidity – Storing String Value in Solidity Efficiently

the problem is not about the string size but about the provided gas, the storage costs more gas as you store more data. so when you increase the string size increase the gas limit provided in your transaction. using the following example :

contract store{
string public storage_;

function store_it(string s){

    storage_=s;
}


}

I've provided a string with 220 character it costs me 774675 gas.

Best Answer

Related Solutions

Solidity – Error When Using String Type as a Mapping Key

Solidity – Storing String Value in Solidity Efficiently

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