decryptAppSecret static method

Implementation

static String decryptAppSecret({required String appId, required String aps}) {
  // 1. Base64 decode both the app_id (key) and aps (the encrypted data)
  final keyBytes = base64Decode(appId); // 32 bytes key
  final rawEncryptedBytes = base64Decode(aps);

  // 2. Split into IV and encrypted message
  final ivBytes = rawEncryptedBytes.sublist(0, 16); // first 16 bytes
  final encryptedMessageBytes = rawEncryptedBytes.sublist(16); // the rest

  // 3. Create AES encrypter
  final key = Key(keyBytes); // 256 bits = 32 bytes
  final iv = IV(ivBytes);
  final encrypter = Encrypter(AES(key, mode: AESMode.ctr, padding: null));

  // 4. Decrypt the message
  final decrypted = encrypter.decrypt(
    Encrypted(encryptedMessageBytes),
    iv: iv,
  );

  return decrypted; // The plain text app-secret
}