Information Systems homework help. __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 = {p_{1}, p_{2}, p_{n,}} and corresponding cipher text = {c_{1}, c_{2}, 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.**

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

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__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__[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