Task 3.

Task 5.

Consider that we train a regression model and run Best Subset selection to obtain a model

Which one of the following is/are true about PCR?? Choose all options that are true. the principle components are orthogonal to each other.

Question 1 (total of 6 marks) Critique the following statement: We achieve security by obscurity: by keeping our algorithms secret we obtain the best guarantee of security. Your answer should cover roughly half a page of A4 paper. (6 marks) (ps: You are strongly encouraged to answer this question using a word processing / typesetting program, e.g., LaTex, Word. Please avoid submitting it handwritten.)

Question 2 (total of 8 marks) Answer the following. a. If & is the DES block cipher, let 2DES denote double encryption with DES with keys Ki and K₂, i.e., 2DESK(P) = DESK, (DESK, (P)) Research and describe, in your own words, how a meet-in-the-middle attack against such cipher might work. (5 marks) (Your description should include what the attacker's goal is, its capabilities, details of the attack and its overall complexity.) b. Write down how encryption works in 3DES with two keys, and give two reasons why this is better than DES. (3 marks)

Task 2. Suppose you have the following algorithm: 1. As an input algorithm is given five (5) unsorted integer arrays of length n. 2. Each array is sorted using bubble sort. 3. Every element of 2nd and 4th array is output on the screen of a user. 4. Number 9 is added to 7th element of 1st, 3rd and 5th arrays. Find how many steps it would take to execute this algorithm (Hint: it should look like equation). Prove that time complexity of this algorithm is O(n²).

Task 1. Answer the following questions based on the RFC of Diffie-Hellman key agreement https://www.ietf.org/rfc/rfc2631.txt. Reference the relevant sections in your answer but use your own words. 1. How the cryptographic keying material derived from the shared secret number is typically used? 2. How the shared secret ZZ is defined? 3. Where the primality test is used? How the the robust primality test is defined? 4. Why the group parameter validation process is needed? 5. What is ephemeral-static mode and how is it different from static-static mode?

Task 4. Using Miller-Rabin prove that 149 is a prime number for witnesses a + 3 and b +4, where a is the 3rd digit of your student code, b is the 4th digit of your student code.

Task 3. Suppose you are given the following encryption scheme: Your task is to provide an attack that shows that given encryption scheme is not secure with respect to the following security game: