CJST 4524 Network Security       Cryptography Assignment        Fall 2015

This problem uses a real world example of a symmetric cipher from an old US Special Forces manual.  Use the very simple example of the cipher from the class lecture to help you answer this assignment.

a) Using the two keys (memory words) cryptographic and network security, encrypt the following message:

“Be at the third pillar from the left outside of the lyceum theatre tonight at seven.  If you are distrustful, bring two friends.”

Make reasonable assumptions about how to treat redundant letters and excess letters in the memory words and how to treat spaces and punctuation.  Indicate what your assumptions are.

b) Decrypt the cyphertext.  Show your work.

c) Comment on when it would be appropriate to use this technique and what its advantages are.