@iden3/js-jwz/dist/node/esm/hash.js

JS implementation of JWZ

import { fromBigEndian } from '@iden3/js-iden3-core';
import { poseidon, sha256 } from '@iden3/js-crypto';
// Q is the order of the integer field (Zq) that fits inside the SNARK.
export const qString = '21888242871839275222246405745257275088548364400416034343698204186575808495617';
export function hash(message) {
    // 1. sha256 hash
    const hashBytes = sha256(message);
    // 2. swap hash before hashing
    const bi = fromBigEndian(hashBytes.reverse());
    let m = BigInt(0);
    if (checkBigIntInField(bi)) {
        m = bi;
    }
    else {
        m = bi % BigInt(qString);
    }
    return poseidon.hash([m]);
}
// checkBigIntInField checks if given *big.Int fits in a Field Q element
export function checkBigIntInField(a) {
    return a < BigInt(qString);
}