Why is it important to distinguish between mechanisms of protection and policies of protection?

1. Why is it important to distinguish between mechanisms of protection and policies of protection? 2. What is an access matrix, and how can it be implemented? 3. How does a virus differ from a worm? 4. What is the difference between symmetric encryption and asymmetric encryption? 5. What are the two main varieties of authentication algorithms?
Part 2: Research Project
In Part 2, you will investigate technical problems of operating systems, and provide a written report. Your research should focus on an in-depth topic about theories, algorithms, approaches, mechanisms, or implementation of one of the following fields of operating systems:
 process management o process and thread o CPU scheduling o synchronization o deadlock handling  storage management o main memory o virtual memory o file systems o mass-storage and I/O  protection and security  distributed, real-time, and multimedia systems
Your topic could come from a sub-problem of cutting-edge research problems discussed in the literature (i.e., investigating a technical problem).