Answer the following questions :

1. The total processing speed of microprocessors (based on clock rate and number of circuits) is doubling roughly every year. Today, a symmetric session key needs to be 100 bits long to be considered strong. How long will a symmetric session key have to be in 30 years to be considered strong? - 5 Marks
2. How do NIST criteria for selection of DES and AES relate to Shanon's original standards of a good cryptographic system? What are the significant differences? How do these standards reflect a changed environment many years after Shannon wrote his standards? - 15 Marks

3. 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.

(a) Explain different ways that this program can be sabotaged so that during execution it computes a different sum, for example, 3 to 20. - 10 Marks
(b) One means of limiting the effect of an untrusted program is confinement: controlling what processes have access to the untrusted program and what access the program has to other processes and data. Explain how confinement would apply to the above example. - 15 Marks

4. The distinction between a covert storage channel and a covert timing channel is not clear-cut. Every timing can be transformed into an equivalent storage channel. Explain how this transformation could be done. - 15 Marks

Part B : 20 Marks

1. Research the TJX data breach caseon the web and answer the following questions.

a. Was the TJX break-in due to a single security weakness or multiple security weaknesses? Explain.
b. Suggest a set of measures which probably would have prevented the TJX data breach. Justify your answer.
c. Which of the CIA goals did TJX fail to achieve in this attack?