I want to retrieve all posts of a blog without username & password

I want to make an android application for my wordpress blog, I want to display there all my blog posts with many options like category wise, date wise, search wise etc…

How Can I retrieve all my blog posts or category wise posts.

Obviously as this will go to each user’s mobile, I don’t want that I comuunicate with my username & pwd.

Please guide me, How can I achieve this?