pwa and mobile client

mobile-client/src/pin.ts

@@ -0,0 +1,17 @@
+import type { PinRecord } from './storage.js';
+
+export const PIN_LENGTH = 4;
+
+async function sha256Hex(text: string): Promise<string> {
+  const digest = await crypto.subtle.digest('SHA-256', new TextEncoder().encode(text));
+  return [...new Uint8Array(digest)].map((b) => b.toString(16).padStart(2, '0')).join('');
+}
+
+export async function createPinRecord(pin: string): Promise<PinRecord> {
+  const salt = [...crypto.getRandomValues(new Uint8Array(16))].map((b) => b.toString(16).padStart(2, '0')).join('');
+  return { salt, hash: await sha256Hex(`${salt}:${pin}`) };
+}
+
+export async function checkPin(pin: string, record: PinRecord): Promise<boolean> {
+  return (await sha256Hex(`${record.salt}:${pin}`)) === record.hash;
+}