xchacha20-js/lib/hchacha20.js

Javascript implementations of ChaCha20, HChaCha20, and XChaCha20

"use strict";

const ChaCha20 = require('./chacha20');
const Util = require('./util');

module.exports = class HChaCha20 extends ChaCha20
{
    /**
     * @param {Buffer} key
     * @param {Buffer} nonce
     * @return {Buffer}
     */
    createHCtx(key, nonce)
    {
        let ctx = Buffer.alloc(64, 0);
        const constant = Buffer.from('657870616e642033322d62797465206b', 'hex');
        Util.toBuffer(Util.bufferToUint32Array(constant)).copy(ctx, 0, 0, 16);
        Util.toBuffer(Util.bufferToUint32Array(key)).copy(ctx, 16, 0, 32);
        Util.toBuffer(Util.bufferToUint32Array(nonce)).copy(ctx, 48, 0, 16);
        return ctx;
    }

    async hChaCha20Bytes(n, k)
    {
        let ctx = this.createHCtx(k, n);
        let x0 = ctx.readInt32BE(0);
        let x1 = ctx.readInt32BE(1 << 2);
        let x2 = ctx.readInt32BE(2 << 2);
        let x3 = ctx.readInt32BE(3 << 2);
        let x4 = ctx.readInt32BE(4 << 2);
        let x5 = ctx.readInt32BE(5 << 2);
        let x6 = ctx.readInt32BE(6 << 2);
        let x7 = ctx.readInt32BE(7 << 2);
        let x8 = ctx.readInt32BE(8 << 2);
        let x9 = ctx.readInt32BE(9 << 2);
        let x10 = ctx.readInt32BE(10 << 2);
        let x11 = ctx.readInt32BE(11 << 2);
        let x12 = ctx.readInt32BE(12 << 2);
        let x13 = ctx.readInt32BE(13 << 2);
        let x14 = ctx.readInt32BE(14 << 2);
        let x15 = ctx.readInt32BE(15 << 2);

        for (let i = 0; i < 10; i++) {
            [x0, x4, x8, x12] = ChaCha20.quarterRound(x0, x4, x8, x12);
            [x1, x5, x9, x13] = ChaCha20.quarterRound(x1, x5, x9, x13);
            [x2, x6, x10, x14] = ChaCha20.quarterRound(x2, x6, x10, x14);
            [x3, x7, x11, x15] = ChaCha20.quarterRound(x3, x7, x11, x15);

            [x0, x5, x10, x15] = ChaCha20.quarterRound(x0, x5, x10, x15);
            [x1, x6, x11, x12] = ChaCha20.quarterRound(x1, x6, x11, x12);
            [x2, x7, x8, x13] = ChaCha20.quarterRound(x2, x7, x8, x13);
            [x3, x4, x9, x14] = ChaCha20.quarterRound(x3, x4, x9, x14);
        }

        return Util.toBuffer(Uint32Array.from([x0, x1, x2, x3, x12, x13, x14, x15]));
    }
};