Afidavit on birth certificate

Hi all!

I need to go to Delhi, to the ministry of external affairs to get an afidavit (some kind of authorisation) on my sons birth certificate so I will be able to register his birth in my country as well.

Any idea how long would that take. How difficult it would be to get it? WOuld i need to do it in person or can i send someone to do it? My baby boy is only a month old and i don't feel like traveling to Delhi with him...I am living in Hyderabad.

Any info would be highly appreciated!!

Thanks!