Implement Secure device lock authentication (biometrics) with offline App PIN support

src/screen/authorised/AppPinService.ts

@@ -0,0 +1,20 @@
+import * as Keychain from 'react-native-keychain';
+
+const PIN_KEY = 'APP_PIN';
+
+export const savePin = async (pin: string) => {
+    await Keychain.setGenericPassword(PIN_KEY, pin, {
+        accessible: Keychain.ACCESSIBLE.WHEN_UNLOCKED,
+    });
+};
+
+export const verifyPin = async (inputPin: string) => {
+    const creds = await Keychain.getGenericPassword();
+    if (!creds) return false;
+    return creds.password === inputPin;
+};
+
+export const isPinSet = async () => {
+    const creds = await Keychain.getGenericPassword();
+    return !!creds;
+};