Encryption Techniques 1

preavi

What is your understanding of the difference between a stream cipher and a block cipher?
What are two ways to launch a cryptanalytic attack against a cipher (based upon what the attacker knows or has in possession)? Be sure to provide detailed examples.
What is your understanding of the difference between an unconditionally secure cipher and a computationally secure cipher?
Your organization has asked for a cryptographic algorithm recommendation for a new project that requires high-level security. What algorithm would you recommend and why?