Assignment 2

(Chapter 2: Classical Encryption Techniques)

Total Marks: 10

Due Date: January 19^th, 2010, by Midnight EST

 Answer any two. If you can solve all three, you will get 5 points extra.

1. Encrypt the message “meet me at clock tower at ten” using the Hill cipher with the key

Show your calculations and the result.          5 points

2. The book shows that the Hill cipher can be broken by a known plaintext attack if there are sufficient plaintext-ciphertext pairs.  Can you solve Hill cipher with chosen plain text? If yes, then describe such an attack.                                   5 points

3. In one of his cases, Sherlock Holmes was confronted with the following message:

534 C2 13 127 36 31 4 17 21 41

DOUGLAS 109 293 5 37 BIRLSTONE

26 BIRLSTONE 9 127 171

Although Watson was puzzled, Holmes immediately deduced the type of cipher. Can you do it too?  (Problem 2.6 from the text book)         5 points