Honestly there probably just wasn't enough time to add all these features to WinRT before the release. I have heard that there will be a huge update in WinRT API's in the future but for now you need to roll your own implementation. I had a similar problem where I needed a sorted collection and I thought that the API's would already have a method to sort but there wasn't any. I ended up just rolling my own, which was a bit annoying but hey you learn CS for a reason right?
You can encrypt your zip files using the crypto libraries. Here's a good resouce http://code.msdn.microsoft.com/windowsapps/CryptoWinRT-54ff3.... I was planning to do that with my app but I never got around to it.