Introduction to Networking s1

MSIT 458 Homework 1

Group Name:

1. Please classify each of the following as a violation of confidentiality, integrity, availability, authenticity, or some combination of these. 1. John copies Mary’s homework. 2. Paul crashes Linda’s system. 3. Carol changes the amount of Angelo’s check from $100 to $1000. 4. Gina forges Roger’s signature on a deed. 5. Rhonda registers the domain name “AddisonWesley.com” and refuses to let the publishing house buy or use that domain name. 6. Henry spoofs Julie’s IP address to pretend to be her.

2. Suppose that you are recommending usage of crypto standards to your CTO for the next generation of IT products in your company. The products aim for the market of the next five to ten years. For symmetric cipher, you will recommend ______, for asymmetric cipher, you will recommend ______, and for secure hash functions (a.k.a., message digest), you will recommend ______.

3. Based on your answers above, please fill in the table below to compare the three crypto mechanisms.

Symmetric Asymmetric Message Digest Cipher Cipher Key length Block size (bits) Output size (given input size n=220 bits) Basic generic N/A structure Permutation used? Substitution used?

4. Message digest are reasonably fast, but here’s a much faster function to compute. Take your message, divide it into 128-bit chunks, and XOR all the chunks together to get a 128-bit result. Do the standard message digest on the result. Is this a good message digest function?