Question

7^(3+j) mod 19 =

(a) 7^j mod 19

(b) 1 mod 19

(c) 7^3 + 7^j mod 19

(d) All of the mentioned are true

I had been asked this question during a job interview.

This is a very interesting question from Number Theory topic in division More Number Theory of Cryptograph & Network Security

Answer 1

The correct choice is (a) 7^j mod 19

To explain I would say: 7^(3+j)  mod 19 = 7^3 * 7^j mod 19 = 7^j mod 19 ( since 7^3 mod 19 = 1 ).