Homework 1.

CSE 5349/7349
Network Security
Homework No. 1
Due on: 02/04/05
1. What are one-time passwords? Do a literature search for one-time passwd
proposed by Leslie Lamport and briefly describe it. What are the advantages and
disadvantages of this approach?
2. Down load the any implementations of AES and encrypt the message Your name
wants to learn Network Security. Hand in your plaintext, cipher key, and cipher
text (be creative about the special ASCII characters). Specify the block size and
key length in AES
3. If a bit error occurs in the transmission of a cipher-text character, how far does the
error propagate? (a) In 8 bit-CFB mode, (b) in 8 bit OFB mode.
4. Using RSA public scheme with p=5, q=11, and d=27, find e and encrypt
“your_lastname”. Use a=01, b=02…z=26.
5. Derive an 8-bit hash code by XORing successive 16 bit blocks and finally
XORing the left byte with the right byte. Now perform B’day attack on the
message “Dallas is a good city” to convert into “Dallas is a bad city”. (Note: Use
8 bit ASCII representation of each character).