Encrypt Cookie in Svelte

cookie.ts

import { env } from '$env/dynamic/private';
import crypto from 'crypto';

const ALGORITHM = 'aes-256-gcm';

export function encrypt(value: string): string {
	const iv = crypto.randomBytes(16),
		cipher = crypto.createCipheriv(ALGORITHM, env.COOKIE_ENCRYPTION_KEY, iv),
		encryptedToken = Buffer.concat([cipher.update(Buffer.from(value, 'utf-8')), cipher.final()]),
		authTag = cipher.getAuthTag();

	return (
		encryptedToken.toString('hex') + '$$' + authTag.toString('hex') + '$$' + iv.toString('hex')
	);
}

export function decrypt(value: string): string {
	const splitValue = value.split('$$'),
		text = Buffer.from(splitValue[0], 'hex'),
		authTag = Buffer.from(splitValue[1], 'hex'),
		iv = Buffer.from(splitValue[2], 'hex'),
		decipher = crypto.createDecipheriv(ALGORITHM, env.COOKIE_ENCRYPTION_KEY, iv);

	decipher.setAuthTag(authTag);

	return Buffer.concat([decipher.update(text), decipher.final()]).toString('utf-8');
}