Assignment No. 02

Semester: Spring 2018
Network Security-CS315

 

Total Marks: 20

 

Due Date: 04/06/2018

Instructions:                          

Please read the following instructions carefully before submitting assignment:

§  You will submit your assignment before or on due date on VU-LMS.

§  Assignment should be completed by your own efforts it should not be copied from internet, handouts or books.

§  You should submit your .doc File via assignment interface at VU-LMS.

§  Assignment sent via Email will not be replied and accepted in any case.

§  If the submitted assignment does not open or file is corrupt, it will not be marked.

§  You will submit solution only in document (.doc or .docx) File.

Objectives:

 

To build the proper understanding of following topics:

a)    Hash Function

b)    Encryption Algorithm

 

For any query about the assignment, contact at cs315@vu.edu.pk

Assignment Questions

 

Question :                                                                                                                                                 Marks 20    

 

Part a)  10 marks

 

Suppose a hacker is trying to attack a secure hash function. Calculate the following to know the level of effort required by hacker if the hash code is of length ‘16’:

·         Pre-image resistant

·         Second pre-image resistant          

·         Collision resistant

 

 

Part b)  10 marks

 

Consider a very simple symmetric block encryption algorithm in which 32-bits blocks of plaintext are encrypted using a 64-bit key. Encryption is defined as

 

C = (P ⊕ K0) + K1

 

Where C  = ciphertext,

 

K secret  = key,

 

K0  = leftmost 64 bits of K,

 

K1  = rightmost 64 bits of K,

 

⊕ = bitwise exclusive OR,

 

+ and is addition mod 264.

 

i. Show the decryption equation. That is, show the equation for P as a function of C,

K0, and K1.

 

ii. Suppose and adversary has access to two sets of plaintexts and their corresponding

ciphertexts and wishes to determine K.We have the two equations: C (P K0) K1; C' (P' K0) K1

 

First, derive an equation in one unknown (e.g., K0). Is it possible to proceed further to solve for K0?

 

 

 

 

 

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