How to use keccak256 sha256 in ink smart contracts?

Question

I want to hash string using sha256 and then store it inside of my ink smart contract.

I tested this code in Rust and it works out for me:

use crypto::sha2::Sha256;
use crypto::digest::Digest;

let phrase = "purchase hobby popular celery evil fantasy someone party position gossip host gather";
let mut seed = Sha256::new();
seed.input_str(&phrase);
let mut bytes = vec![0; seed.output_bytes()];

However, this code doesn't compile in ink, because ink can't seem to use crypto crate...

How can I use keccak256 inside of an ink smart contract to return me Vec ?

I found package Sha2x256, but I'm unsure how I should use this?

Answer 1

You can use ink_env::hash module.

Then your hash function would look something like this

    use ink_env::hash;

    pub fn hash_keccak_256(input: &[u8]) -> [u8; 32] {
        let mut output = <hash::Keccak256 as hash::HashOutput>::Type::default();
        ink_env::hash_bytes::<hash::Keccak256>(input, &mut output);
        output
    }

input ofc is the bytes representation of the hashed value.

For ink! 4 replace ink_env with ink::env