SHW5 - Solutions for HW 5 From 8.7 Exercise 3 One-time pads...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Solutions for HW 5 From 8.7 Exercise 3 One-time pads are rarely used in practise because of the problem of key distribution. As the key must be completely random, it must be generated and distributed using some secure medium (usually by courier). Further, the sender and receiver must ensure they stay synchronized, so the recipient knows where in the key sequence the senders key begins. Exercise 10 Prove the following: a) If p is a prime, (p) = p1. The residue set Z p = {0, 1, , p-1} Note that except for 0, p is relatively prime to each element in Z p . Hence ( p ) = p 1 b) If p and q are primes, (pq) = (p-1)(q-1). The residue set is Z pq = {0, 1, , pq-1} A number that is a multiple of p or q is not relatively prime to pq . Hence, elements of sets { p , 2 p , 3 p , .., ( q-1) p } and { q , 2 q , 3 q , , ( p-1) q } are not relatively prime to pq . Also note that 0 is not relatively prime to pq )....
View Full Document

This note was uploaded on 11/02/2009 for the course SIS 2150 taught by Professor Joshi during the Spring '09 term at Philadelphia.

Page1 / 4

SHW5 - Solutions for HW 5 From 8.7 Exercise 3 One-time pads...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online