Who was India's 'Black Tiger' Ravindra Kaushik, who went to Pakistan as spy at 23?

Indian spy Ravindra Kaushik, hailed as 'Black Tiger', was recruited by RAW in 1970s. Born in Rajasthan, he travelled to Pakistan at 23 and got enrolled into Karachi University as Nabi Ahmed Shakir. After joining Pakistani Army, he relayed key intelligence to India. Kaushik was arrested in 1983 after communication link failed, following which he died in jail in 2001.