Question

The GCD of x^5+ x^4+ x^3– x^2 – x + 1 and x^3 + x^2+ x + 1 over GF(3) is

(a) 1

(b) x

(c) x + 1

(d) x^2 + 1

The question was posed to me in final exam.

This intriguing question comes from Overview in chapter Cryptography Overview, TCP/IP and Communication Networks of Cryptograph & Network Security

Answer 1

The correct choice is (c) x + 1

To elaborate: The GCD ofx^5+ x^4+ x^3 – x^2 – x + 1 and x^3 + x^2+ x + 1 over GF(3) is x + 1.