Data Hiding and Encapsulation are frequently mistaken for security by first time oops learners. Its important to understand that data hiding and encapsulation have nothing to do with security.
These concepts exist to ensure that inheritance of a class A, from class B (class B extends A) does not inherit the "encapsulated" members.
I hope this kinda clarifies your confusion, and also motivates you to read and study more. Your question is very basic to the OOPS concepts. And the interviewer is not trying to corner, you but ask you very basic questions on OOPS. Study hard!!!