CSC 300: Assignment 7
Total: (43 pts + 10 pts E.C.)
1. (10 pts) Determine if 667 is a prime, and if not find its prime factors, using the procedure
shown in class.
2. (3+3 pts) Exercise 2 under 3.8 (page 254-255).
3. (6X3 pts) Exercise 4 under 3.8 (page 255).
4. (3X3 pts) Exercise 28 under 3.8 (page 256).
5. (10 pts; Extra Credits) Can you apply the idea of using the computational hardness of finding
the prime factors of a large composite, to enable two people, A and B, to perform a coin toss
over the telephone, such that none of them has any reason to suspect that the other person
cheated? This means, say A tosses, B makes the call ('H' or 'T') over the telephone, A verifies it,
but somehow B is satisfied that A has not cheated even though he did not personally witness the
toss. They will clearly need to exchange more information (relating to security) than I just
outlined. Can you specify the exact procedure? Credits only for clear answers.