Beginning Webservice with Joomla 2.5

I am new to joomla 2.5. I need to design application which is to be used by STB(SET TOP BOX) or TV Application. Is it possible to use below features with Joomla 2.5 ?

1. Authenticate users where credentials are passed from STB or TV via POST method.
2. Calling Webservices after authentication, custom string format needs to be return instead of JSON or XML.
3. Is it possible to host file with encryption from developed administrator component ?
Any Ideas? Any good beginners book for Joomla 2.5 ?

Thanks