Encrypting the cache manifest HTML5 app iOS

I have a web app written for iOS/Android/Playbook and it works by pulling data from a cloud source and then displ开发者_JS百科aying secure data from a server in our company firewall alongside it. I am looking to make this app work offline but I am wondering whether or not the cache on iOS (similarly Android etc) can be encrypted and is accessible only by the app I have written.