Assignment 6

Due Wednesday March 29, 2017 6:50pm via sakai


Please answer the questions precisely and concisely. Every question can be answered in one or at most a few sentences. I will not have the patience to read long paragraphs or essays and you may lose credit for possibly correct answers.


Text: Ross Anderson, Security Engineering: Chapter 5, pages 129–182
Entire chapter: Cryptography


  1. What is a necessary condition for perfect secrecy?

  2. Explain the following terms:
    (a) Backward secrecy (the text refers to it as backward security)
    (b) Forward secrecy (also known as perfect forward secrecy; the text uses the terms forward secrecy and forward security interchangably)

  3. How did Robert Hooke establish priority for his invention without revealing the invention?

  4. What are the three properties of hash functions?

  5. What is an advantage of counter encryption over cipher block chaining (CBC)?