Unit 5 Homework

Textbook Problems

SSH, AFS , and Kerberos. Why can't we use SSH Public Key authentication on GL? How could this be fixed?
rc4-die-die-die. There is a draft RFC calling for the use of RC4 with SSH to be deprecated. What is the argument for deprecating RC4? Do you agree? You will need to read one ore more RFCs referenced by the draft.
Kerberos v4 vs. Kerberos v5. What are the major differences between Kerberos v4 and v5? Pick one difference and explain why it matters.
ARP poisoning defense. Research and describe two methods for protecting against ARP cache poisoning.
Another QC algorithm. Research Grover's Algorithm and summarize what sorts of problems it can solve. Considering all the cryptographic algorithms we have discussed, are there any for which Grover's Algorithm poses a practical threat (assuming a QC of the appropriate size could be built).

For the remaining problems, refer to the original paper by Needham and Schroeder.

N-S with PK. Summarize the public key-based Needham-Schroeder protocol.
A question of integrity. Explain the following statement from the paper: “…double encryption, i.e. {{message}^SKA}^PKB, or some equivalent, is required…”
AS implementation. Explain the differences in the Authentication Server (AS) implementation for symmetric vs. public key versions of Needham-Schroeder.
One-Way Communication. Summarize the protocol for One-Way Communication for both symmetric and public key implementations. For what applications might this be useful?