1. CSC 386 – Computer Security Scott Heggen

2. Agenda Emmanuel Tachu will present his work from an independent study on Networking Cryptography Primer

3. Last Week’s Homework Bell-LaPadula Model Deadline extended until 11:55pm today

4. Cryptography Primer AliceBob m Eve

5. Cryptography Primer AliceBob Eve k k m E C = E(k,m) m D

6. Symmetric Key Both Alice and Bob’s key are the same Must be shared prior to communications What is the key?

7. Substitution Cipher (Caesar Cipher) AC BE CF DG EH FI GJ …… k = AliceBob Eve k k “bad egg” E C = E(k,m) = “egc hjj” “bad egg” D “egc hjj”

8. Assignment For Friday: Create a Python script which takes in two files: message.txt and key.txt The message.txt file can contain any message you chose to send me The key.txt file must contain your B-number, without the letter B The Python script must compute C using the message and the key. Your encryption algorithm E should be a simple substitution cipher which shifts each letter of message by the integer value in key. Submit to Moodle: Your Python Script coded_message.txt