Yes. It’s legal. IND stands for India. 

In 2005 the Govt. amended the Central Motor Vehicles Rules, 1989. The amendment introduced High Security Number Plates or High Security Registration Plates (HSRPs). It also introduced some features to High Security Number Plates. IND is a feature of High Security Number Plates. High security plates are for protection and to enable easy tracking of lost or stolen vehicles. On December 6, 2018, Govt. of India notified that it’s mandatory for all vehicles sold on or after April 1, 2019, to have High Security Number Plates.