Module 8 Overview

March 1-7 · Reading: 9 pages · Estimated total: 6.5 hours

Symmetric cryptography works beautifully once two parties share a key. Getting them to share one is the problem it cannot solve. Two people who have never met, on a network run by strangers, cannot agree on a secret by exchanging messages that everyone can read, not with symmetric tools.

Public-key cryptography solves that, by making one half of a key pair publishable. This week covers what that buys: encryption to someone you have never met, and signatures that prove a message came from a particular key and has not changed.

It also sets up the gap that week 10 exists to fill. A signature verifies against a key. Nothing this week tells you the key belongs to the person you think it does.

Learning Objectives

By the end of this week, the successful student will be able to:

• 3.3: Compare symmetric and public-key cryptography by key distribution, performance, and typical use.
• 3.4: Verify a digital signature and explain what a verification failure does and does not prove.

Assignments and Tasks

Due by Sunday at 11:59 p.m. Mountain Time

• Read 8.01 Readings and Lecture Notes and run sign_demo.py (2 hrs 30 min)
• 8.02 Lab 5: Hashing and Signatures (1 hr 30 min, 38 points)

Next week is review and catch-up with no new material, so this is the last week of new content before the break.

Time Estimate

Activity	Time
Reading (9 pages plus Nakov)	1 hr 45 min
The notes page and running sign_demo.py	45 min
Lab 5	1 hr 30 min
Review and slack	2 hrs 30 min
Total	~6.5 hrs