crypto.ts

1	const AES_PARAMS = { name: 'AES-GCM', length: 256 };
2	const IV_BYTES = 12;
3
4	export const generateRoomKey = () =>
5	crypto.subtle.generateKey(AES_PARAMS, true, ['encrypt', 'decrypt']);
6
7	export const exportRoomKey = async (key: CryptoKey) => {
8	const raw = await crypto.subtle.exportKey('raw', key);
9	return btoa(String.fromCharCode(...new Uint8Array(raw)))
10	.replace(/\+/g, '-').replace(/\//g, '_').replace(/=/g, '');
11	};
12
13	export const importRoomKey = async (base64url: string) => {
14	const b64 = base64url.replace(/-/g, '+').replace(/_/g, '/');
15	const padded = b64 + '='.repeat((4 - (b64.length % 4)) % 4);
16	const raw = Uint8Array.from(atob(padded), (c) => c.charCodeAt(0));
17	return crypto.subtle.importKey('raw', raw, AES_PARAMS, false, ['encrypt', 'decrypt']);
18	};
19
20	export const encryptJson = async (key: CryptoKey, value: unknown) => {
21	const iv = crypto.getRandomValues(new Uint8Array(IV_BYTES));
22	const plaintext = new TextEncoder().encode(JSON.stringify(value));
23	const ciphertext = await crypto.subtle.encrypt({ name: 'AES-GCM', iv }, key, plaintext);
24	const ivB64 = btoa(String.fromCharCode(...iv));
25	const ctB64 = btoa(String.fromCharCode(...new Uint8Array(ciphertext)));
26	return `${ivB64}:${ctB64}`;
27	};
28
29	export const decryptJson = async (key: CryptoKey, encryptedValue: string) => {
30	const [ivB64, ctB64] = encryptedValue.split(':');
31	const iv = Uint8Array.from(atob(ivB64), (c) => c.charCodeAt(0));
32	const ciphertext = Uint8Array.from(atob(ctB64), (c) => c.charCodeAt(0));
33	const plaintext = await crypto.subtle.decrypt({ name: 'AES-GCM', iv }, key, ciphertext);
34	return JSON.parse(new TextDecoder().decode(plaintext));
35	};