National College of IrelandMSC in Cyber Security-Year 1- MSCCYB1_JAN21I Semester 3 2020/2021 ______________________________________________________________________Cryptography CA Test (Open Book)...

National College of IrelandMSC in Cyber Security-Year 1- MSCCYB1_JAN21I Semester 3 2020/2021 ______________________________________________________________________Cryptography CA Test (Open Book) Weighting: 40%Release Date for MSCCYB1_JAN21I- Tuesday, 29/06/2021 at 4:30pm Submission Date for MSCCYB1_JAN21I- Wednesday, 30/06/2021 at 10amChetna SharmaDr Evgeniia Jayasekera Dr Nhien An Le KhacInstructions1. This is an open book Assessment.2. You are allowed to use your class notes. However, you are not allowed to discuss your solution withother students. If it is found that a student has discussed his/her solution with other students, thecase will be referred to disciplinary committee.3. This is a Turnitin assignment. It will be used to check whether a text is copied from Internet, any other source or peer students.4. You need to submit the solution of this CA in your Moodle page at the CA Submission Link. You should submit the PDF (or DOC) file by the end of your exam time. Page 1 of 3
5. You can also draw on a piece of paper, take a picture with your mobile phone camera then you submit the photo on Moodle. Please ensure that you write below your drawing the question number the drawing corresponds to.6. Use a single column layout document.7. Font size for the body of the text should be 12 point Times New Roman/ Arial.8. Include student name, student ID and course name (e.g. MSCCYB, PGDCYB) at the top of the first page9. The question number being addressed must be clearly indicated in the document.10. Please submit your solution on time.11. Limit your answer to a maximum of 500 words.Attempt all questionsQuestion 1:Find the value of N using the following calculations:A) Choose the last digit of your student id number. Let this digit be E. For example, if your student id number is x198762, E is 2.B) Choose a random number between 10 and 40. Let this number be R.C) Add R and E i.e., R+E. Let this number be N.Question 2:(5)A symmetric key encryption algorithm is as follows: m ⊕ k ⊕ ......N times............ ⊕K. Here, m signifies the message, k signifies the key, and N signifies the number calculated in Question 1. Answer the following questions:A) Is the algorithm above a valid encryption algorithm and why?B) In case the answer to A is "yes", what is a symmetric key decryption algorithm?If the answer is "no", then how many more ⊕ k operations have to be done to make it a valid encryption algorithm?(10+10)Question 3: Perform the following tasks:A) Select a random plaintext of N characters (N is calculated in Question 1).B) Apply the Vigenère cipher to the considered plaintext and obtain the ciphertext.It is your choice to choose whichever key you prefer.Page 2 of 3
C) Let's suppose an attacker gets the ciphertext (determined in Question B). Demonstrate how the attacker can break the Vigenère cipher and get the plaintext. Clearly explain each step.(5 + 15 +25)Question 4:In symmetric-key cryptography, how many keys would be required if every student in a group of N students (N calculated in Question 1) had to communicate with every other student in another group of 4 students?Question 5:Explain Perfect Secrecy in terms of the random plaintext selected in Question 3.(15)(15)Page 3 of 3
Jun 29, 2021
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