Question 1: Is RC4 a symmetric or asymmetric block or stream cipher? Why is it popular? And why does NIST still want to define a new standard (AES)?
Question 2: Under what situations should three classes of algorithms be used: hashes, symmetric, and asymmetric, respectively?
Question 3: Describe one example where the public-key algorithm can be used together with the symmetric-key algorithm? Why do you think the combination makes sense?