Web Crypto - Key Generation, Export, and Import

crypto-key.js

import { webcrypto as crypto } from 'node:crypto'; // Node.js only

/* Generate */

const key = await crypto.subtle.generateKey(
	{
		name: 'AES-GCM',
		length: 256
	},
	true,
	['encrypt', 'decrypt']
);

/* Export */

const exportedKeyBuffer = await crypto.subtle.exportKey('raw', key);
const exportedKeyArray = new Uint32Array(exportedKeyBuffer); // 256 bit / 32 bit = 8

const OTP_SECRET = exportedKeyArray.toString();
// e.g. '42750835,1826404814,1276682799,609486549,910848504,1236505811,2679575580,955180990'

/* Import */

const array = OTP_SECRET.split(',').map((string) => Number(string));
// e.g. [42750835,1826404814,1276682799,609486549,910848504,1236505811,2679575580,955180990]

export const otpKey = await crypto.subtle.importKey(
	'raw',
	new Uint32Array(array),
	'AES-GCM',
	true,
	['encrypt', 'decrypt']
);