Various Links CS190 Homepage Cryptography Discussion Topics Cryptography Class Homework Cryptography White Paper by Slackers CS190 Homework Homework #1 Homework #2 Homework #3 Homework #4 Other Groups Homework Push Technology VRML Network Agents Audio Streaming Java Group Cryptography Resources Cryptography FAQs Induhvidual Home Pages Tim Grean Brandon UCSD Computer Related ACM - UCSD UCSD CSE Page This page can be viewed with: And maybe this but no guarantees: Join the DNRC:

Slackers Group : Cryptoraphy Class Homework Assignment : Simple secret-key encryption exercise. A simple example of a secret-key encryption: create a key (a random string) perform an XOR between the characters in the key and characters of the encrypted message to decode the message, perform an XOR on the encrypted message with the same key original string 101111 key 101010 encrypted string 000101 --- transmission --- encrypted string 000101 key 101010 original string 101111 The XOR algorithm is a polyalphabetic substitution cipher. Assignment is to write a program to perform this type of encryption. In the example above, it was a 6 bit key and 6 bit block. We'll use 16 bit blocks and a 16 bit key (an int). This assignment only requires you to encrypt numeric messages rather than ascii characters to avoid complexity, but if you are so inclined to do so you'll get extra extra credit! So basically your program should: take as input the plaintext numeric message encrypt it using a key that you designate with the XOR scheme print out the encrypted message pretend its sent the message somewhere decrypt the ciphertext then print out the resulting plaintext. Copyright 1997 by Slackers Union. Comments should go to any of the group members. Opinions reflected on this page are by no means opinions of UCSD. Go sue somebody else. Last Modified: April 21, 1997