static func loadPassProtected(key: String, context: LAContext? = nil) -> Data? {
        var query: [String: Any] = [
            kSecClass as String       : kSecClassGenericPassword,
            kSecAttrAccount as String : key,
            kSecReturnData as String  : kCFBooleanTrue,
            kSecAttrAccessControl as String: getPwSecAccessControl(),
            kSecMatchLimit as String  : kSecMatchLimitOne]

        if let context = context {
            query[kSecUseAuthenticationContext as String] = context

            // Prevent system UI from automatically requesting password
            // if the password inside supplied context is wrong
            query[kSecUseAuthenticationUI as String] = kSecUseAuthenticationUIFail
        }

        var dataTypeRef: AnyObject? = nil

        let status = SecItemCopyMatching(query as CFDictionary, &dataTypeRef)

        if status == noErr {
            return (dataTypeRef! as! Data)
        } else {
            return nil
        }
    }