A free app for Android, by Hide Apps NO ROOT.

The finest privacy protector when browsing the web is Private Browser. When you enter your PIN into the phone’s calculator, Private Browser can pretend to be a calculator and transform into a fully functional, incredibly fast browser.

The calculator can be used to conceal the private browser; it includes standard calculation features, and the password must be entered there in order to access the browser interface. The downloaded file is secured by the browser. Only the browser can recognize and open files like videos and photos; neither other applications nor system libraries can. You do not nedd to worry when using this app.