functionalscript/crypto/sign/module.f.js

FunctionalScript is a purely functional subset of JavaScript

import { listToVec, msb, uint, vec, vec8, length } from "../../types/bit_vec/module.f.js";
import { hmac } from "../hmac/module.f.js";
import { curve } from "../secp/module.f.js";
const concat = listToVec(msb);
const v00 = vec8(0x00n);
const v01 = vec8(0x01n);
/**
 * The size of the result equals the size of the hash.
 *
 * @param sha2 SHA2 hash function
 * @returns A function that accepts a private key, a message hash and returns `k`.
 */
const createK = (sha2) => {
    const h = hmac(sha2);
    let vs = vec(sha2.hashLength);
    let k0 = vs(0x00n);
    let v0 = vs(0x01n);
    return (privateKey) => (messageHash) => {
        const pm = concat([privateKey, messageHash]);
        let k = k0;
        let v = v0;
        k = h(k)(concat([v, v00, pm]));
        v = h(k)(v);
        k = h(k)(concat([v, v01, pm]));
        v = h(k)(v);
        return uint(h(k)(v));
    };
};
export const newPrivateKey = (i) => (random) => {
    const { nf } = curve(i);
    if (length(nf.max) < length(random)) {
        throw "need more random bits";
    }
    return uint(random) % nf.p;
};
export const sign = (sha2) => (curveInit) => (privateKey) => (messageHash) => {
    const { mul, pf } = curve(curveInit);
    // const curveVec = vec(length(pf.max))
    //`k` is a unique for each `z` and secret.
    const k = createK(sha2)(privateKey)(messageHash) % pf.p;
    // `R = G * k`.
    const rp = mul(curveInit.g)(k);
    // `r = R.x`
    const r = rp === null ? 0n : rp[0];
    // `s = ((z + r * d) / k)`.
    const d = uint(privateKey);
    const z = uint(messageHash);
    const rd = pf.mul(r)(d);
    const zrd = pf.add(z)(rd);
    const kn1 = pf.reciprocal(k);
    const s = pf.mul(zrd)(kn1);
    return [r, s];
};