Cybersecurity Seminar 09 -- Ciphers

1. What are the differences between Block and Stream Cipher?

2. What are the differences between Synchronous and Self-synchronous stream cipher?

3. If all the links on the end-to-end path from the source host to the destination host are reliable,

   1. What is the most reliable encryption for a file transfer application? Why?
   2. What is the most reliable encryption for a music stream application? Why?

4. Suppose that amongst eight people each pair wants to be able to communicate securely without any risk of eavesdropping.

   1. How many different keys will they need in total if they use a symmetric encryption algorithm and how many if they use an asymmetric encryption algorithm?
   2. How many keys does a person have to store secretly in both cases?