Passing parameters in the message header with a REST API

Question

Hi,

I'm developping a REST API and I need to tranport cryptograms to authenticate the message for each request in a applicative process (MAC encryption from secret keys). I was thinking about putting them in the message header to avoid adding non-data information in the message body which contains the posted/retrieved object (XML or JSON).

Is it a best practise ?

Can I add as many parameters I want in the header ? I've read that I must prefix them with "x-". The behavior of this parameter is exactly the same than Path or Query params ?

I'm using Jersey.

Thank you for you help.