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# any one have CS315 2nd Assignment

 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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