hw4 - CMPSCI 177 - Computer Security Fall 2011 Fourth...

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CMPSCI 177 - Computer Security Fall 2011 Fourth Homework - DES and Public Key Due: Tuesday ,25OCT 11 2:00pm Part I: DES 1. Consider the following 64 bit key: 1000110110001011101101001010100111101011001010011011001011001100 What is the value of the key used for the fourth round of the DES encryption algorithm? 2. Consider the following 48 bit string: 101101010110011010110000010101011001101111011011 If this string is input to the s boxes in the DES encryption algorithm, what string is output from the s boxes? Part II: Public Key 1. What is the totient of 36? Defend your answer. 2. Use the superincreasing sequence S=[2,4,9,17,34,69,146], modulus n=311, and multiplier w=19 to gen- erate a public key sequence H for Merkle-Hellman. 3. Assume that you receivedthe ciphertext C=101 from someone using the public key generated in exer- cise 2. Youare to decipher C and determine the message M that was used to generate C.
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hw4 - CMPSCI 177 - Computer Security Fall 2011 Fourth...

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