Get Fresh Answer: INFA 640- Cryptography and Data Protection

Instructions

• Take this test during the week (with late submission Monday; a maximum of 10% penalty) Work alone. You may not confer with other class members, or anyone else, directly or by e-mail or otherwise, regarding the questions, issues or your answers. You may use your notes, OER, textbooks, and other published materials.
• It is scored based on 100 points for the test. It is 25% of your class grade.
• When composing your answers, be thorough. Do not simply examine one alternative if two or more alternatives exist. However, choose only one as your answer giving reasons for your choice. The more complete your answer, the higher your score will be. Be sure to identify any assumptions you are making in developing your answers and describe how your answer would change if the assumptions were different. For multiple choice questions if you think there are two correct answers choose the best one and justify your answers. Please write justification in your own words, [if you choose both you will get 50%] avoid cut and paste or merely copying the sentences from references or other places from the Internet. If you are describing methodology, please describe it in sufficient details so that by following it, anybody can reach the same result without additional help from you.
• While composing your answers, be VERY careful to cite your sources. Use only reputable sources. Personal blogs or the websites that are set up for sellling are not reputable sources.  Remember, failure to cite sources constitutes an academic integrity violation.
• For Parts I and II, when you are providing justification, as I mentioned above, reference is required.  If you are giving reference of a book, I will need page number(s). I cannot go through the complete book to verify your reference.
• Your answers should be contained in a Microsoft Word (or compatible format that can be opened by MSWord) document, uploaded to your assignments folder. If you use some other word processor, please make sure that the numbering does not change. I will return files (ungraded) in any other format if I cannot open them in one try. I may also check your part III answers with Turnitin.
• Please submit questions regarding the exam to your instructor at [email protected]. Since I can check the emails on my smart phone, I check email a lot more often than “questions to instructor” section in LEO. If questions submitted are generic, I will post them in the discussion area or as a new news item.
• Please be sure to put your name   in the header on every page including page #’s.
• You will be getting an absolute grade out of 100 for this test. However, the final course grade will depend on the relative performance of the class.
• Name your file “Last name First name INFA640 Midterm”. Replace “Last name” with your last name and so on. Naming files as instructed will help me to save time. I have encountered files without your name which I may return ungraded _________________________________________________________________________

Part I (Each 4 Pts. Total 40.) Choose the best one. Please provide reason of your choice in a few sentences or reasons not choosing the other choices. Reason must be in your own words. Use guidelines for reference as given in the instructions.

1. 1. To protect information, it is sufficient to protect against possible virus threats: True/False  justify your answer
2. Which are the weaknesses of a shift cipher?
   1.  Natural language letter frequency makes them easy to decode.
   2. The number of letters in the alphabet makes them easy to decode.
   3.  Once the shift is determined the message is decoded.
   4.  Once you have the code book you can decode the message instantly
   5. A&B
   6. A, B & C
   7. A, B, C and D
   8. A & C

No reason required

1. What is the basis of the modern cryptography? _________________
   1. the laws of mathematics
   2. manipulation of data
   3. creating disguises for information
   4. none of the above

Reason:

 

1. Historically, the primary and compelling reason for advances in cryptography has been _____________.
   1. protecting business assets
   2. the need for individual privacy
   3. wars
   4. keeping diplomatic conversations secret

Reason: _

1. A _______________ requires that the cipher alphabet changes throughout the encryption process.
   1. monoalphabetic substitution cipher
   2. polyalphabetic substitution cipher
   3. quantum cipher
   4. alphanumeric shift cipher

Reason: _

1. one of the Network threats is   
2. buffer overflow
3. slowing the computer
4. denial of service
5. computer lock up

how does it happen: _

1. Risk is __.
   1. a weakness in the system
   2. a circumstance that may cause loss or is possible danger
   3. is a vulnerability that can be exploited
   4. Nothing to worry about

Reason: _

1. The trustworthiness of a system is diminished because of.
   1. exposure to risks
   2. demand for keys
   3. confidence decreases
   4. bad weather

Reason: _

1. The _______ controls the action of the algorithm.
   1. The receiver
   2. the length of the plain text
   3. cipher text
   4. key

Reason:

1. What has become a major web problem with respect to security?
   1. scripting errors
   2. mapping attacks
   3. on-line surveys
   4. user ignorance

Reason: _

______________________________________________________________________________Part II (6 points each, Total 30)

Q1a     Complete the following Truth Table: F denotes false and T denotes true

A	B	C=A or B	D= A xor B	E= A and B
F	F
F	T
T	T
T	F

Q1b In the following Θ denotes one of the following operators: ’or’, ‘xor’ or ‘and’.

Input1 Θ input2 = Result  

where, input1 and, Inpuut2 are ‘A’ and ‘B’ and Results are C, D, or E from the above table.

Which operation will yield? (what is Θ?)

input1 Θ result = input 2

input2 Θ result = input 1

Please show proof for one, or disprove other two

Hint:

Check

Input1 OR result = Input2?

Input2 OR result = Input1?  For results C, D and E, and inputs A and B

Repeat replacing OR with AND, and XOR

As soon as the given operator is not valid for an operation go to the next operator.

Please show proof. Without proof you will get partial credit only

Q2       Using the English alphabet (i.e., mod 26 arithmetic) let plaintext = {p₁, p₂, p_n,} and corresponding cipher text = {c₁, c₂, c_n}.

{start A as 1, B as 2 and so on}

Suppose the encryption function is c_i = p_i + 8 (mod 26). 

You receive the cipher text message CUCKQAVWECUOK

What type of cipher is this?

What is the decryption function, and the decrypted/recovered plaintext, (insert spaces to make readable)?

Show all your steps.

Q3       You are Alice. You have agreed with your friend Bob that you will use the Diffie-Hellman public-key algorithm to exchange secret keys. You and Bob have agreed to use the public base g = 7 and public modulus p = 941.  

You have secretly picked the value S_A = 17 You begin the session by sending Bob your calculated value of T_A. Bob responds by sending you the value T_B = 268. 

What is the value of T_A

What is the value of your shared secret key?

Can you guess Bob’s secret value S_B and what it would be?

Show each and every step of your calculations, if you use Excel for mod calculation include the spreadsheet, for any other method include the screenshot of that method

[without the spreadsheet or screenshot, you will not get the full credit]

for mod calculation, the following identity may be useful

mod(X*Y,p) = mod[mod(X,p)*mod(Y,p),p]

mod ( X^n, p) = mod [mod(X^k, p)*mod(X^m, p), p]; where k+m=n

e.g. mod (X^17, 941) = mod [mod (X^8, 941) *mod (X^9, 941), 941]; where 8+9=17

Q4       Bob believes that he has come up with a nifty hash function. He assigns a numeric value V_Char to each letter in the alphabet equal to the letter’s position in the alphabet, i.e., V_A = 1, V_B = 2, …, V_Z = 26. For a message, he calculates the hash value H = (V_{Char 1} x V_{Char 2} x V_{Char 3 …}x V_{Char N}) mod (26).

Bob uses this function to send a one-word message, “FATHER” to his supervisor Bill, along with his calculated hash value for the message. Alice is able to intercept the message and generates an alternative message that has a hash value that collides with Bob’s original hash value.

Give definition and properties of the hash function.

Show a message that Alice may have used to spoof Bob’s message and demonstrate that its hash value collides with Bob’s original hash.

Q5       Consider the following plaintext message: IT IS EXCITING TO KNOW THAT WE MAY HAVE FOUND A PLANET SIMILAR TO EARTH MATTER IN THE UNIVERSE.

1. (3 pts) If this message is sent unencrypted and successfully received, what is its entropy? And why?
2. (3 pts) If this message is encrypted with DES using a random 56-bit key, what is the encrypted message’s entropy?  And why
3. _____________________________________________________________________

Part III

Essay Question:   Length: 800- 900 words.  Use APA format for in-line citations and references.  (30 pts.)

Compare and contrast symmetric and asymmetric encryption algorithms.

• Your response should include a brief overview of the cryptographic basis for each type of algorithm, and a comparison of their strengths and vulnerabilities. [20 pts]
• Describe how a hacker might go about cracking a message encrypted with each type of algorithm. [6 pts]
• Suggest a specific application for each type of algorithm (symmetric and asymmetric) where the advantages clearly outweigh the disadvantages. [4 pts]
• Remember to address all points