Question

Find the primitive roots of G = <Z10*, ×>.

(a) {2, 6, 8}

(b) {3,6 ,9}

(c) {3, 7, 8}

(d) {3, 7}

I got this question by my college director while I was bunking the class.

My enquiry is from Number Theory in chapter More Number Theory of Cryptograph & Network Security

Answer 1

Correct option is (c) {3, 7, 8}

The explanation is: Number of primitive roots = f(f(11))=f((111-110)) = f(10)  = f(2). f(5)

      = (21-20)(51-50) = 1 x 4 = 4

The primitive roots of this set are {3, 7}.