Create a desktop app for Windows

We have a web based test (exam) application with backend developed in laravel for which we need to create a desktop app for Windows. The same will be used by students to do competitive tests. Tests are created at the backend, but need to down load the MCQ question paper file in encrypted format, which can be opened only by this desktop app. The test can then be answered without using internet. On completion of the test, the marked answers can then be sent to the server to validate with the correct answers and a result can be seen.