1. Alice and Bob are both users of PKI. Explain how they use their keys to communicate when Alice sends a private message to Bob, and provides proof that she sent the message.
2. A program is written to compute the sum of the integers from 1 to 10. The programmer, well trained in reusability and maintainability, writes the program so that it computes the sum of the numbers from k to n. However, a team of security specialists scrutinizes the code. The team certifies that this program properly sets k to 1 and n to 10; therefore, the program is certified as being properly restricted in that it always operates on precisely the range 1 to 10. List different ways that this program can be sabotaged so that during execution it computes a different sum, for example, 3 to 20.
3. a) Cite a situation in which the sensitivity of an aggregate is greater than that of its constituent values. b) Cite a situation in which the sensitivity of an aggregate is less than that of its constituent values.
4. The old human telephone "switches" were quaint but very slow. You would signal the operator and say you wanted to speak to Jill, but the operator, knowing Jill was visiting Sally, would connect you there. Other than slowness or inefficiency, what are two other disadvantages of this scheme?