Is it permissible for students to open books during an electronic exam—with the university's knowledge and silence—based on the principle of "Silence in the context of need is an affirmation"?

An examination determines a student's level of achievement, and it is not permissible for a student to open a book or copy from it during the exam, even if the university remains silent about it. The university's silence is considered a dereliction of its duty. Whoever is certain that students are doing this must inform the university administration to clear their conscience.