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First-Exam2-20-07

# First-Exam2-20-07 - First Examination CIS 4363 Name 1 In...

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First Examination CIS 4363 February 20, 2007 Name____________________________________________________________ 1. In this problem you will use a modified RC4 cipher. The text is encrypted at half a byte, 4 bits, at a time. Let’s call half a byte, 4 bits, as a unit. Vector S will be 16-unit long, from S[0] to S[15]. Each S[i] will have 4 bits, containing a number from 0 to 15. K will have a length equal or less then 16 units. Find the cipher text using the given K and plaintext. Assume that K is given in hex as xE3A. (i) Provide the contents of T after initialization. (2 points) (ii) Compute the contents of S after two iterations through the initial permutations of S. (4 points) (iii) Assume that the results obtained in (ii) are used in stream generation. What is the cipher text generated for the plaintext given in hex as xD5A. (9 points) 2. In this problem you will use a modified ECB cipher. Instead of encrypting 64 bits at a time, encrypt a fixed length of characters at a time using Hill cipher. Find the cipher text using the given Hill cipher key and plaintext.

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First-Exam2-20-07 - First Examination CIS 4363 Name 1 In...

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