midterm1-sample-s12 - CNT 5412 Network Security (Partial)...

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CNT 5412 Network Security (Partial) Midterm 1 – Sample Questions February 2012 NAME_________________________________________________________________ Instructions: Put your name on your exam. Do all problems. Points are indicated next to the problem. 1. 16 pts 2. 16 pts 3. 12 pts 4. 28 pts
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1. (16 pts) You know that the following ciphertext has been encrypted using a monoalphabetic cipher: SCHK SUKS HK CPEOLT UPKT a. Determine the index of coincidence (IC) for this cipher. Is this ciphertext more likely random text (IC = 0.038) or English (IC = 0.065)? Show your work. b. How many different monoalphabetic ciphers are there? c. If you were asked to cryptanalyze the above cipher briefly indicate what your next steps would be. 2. (16 pts) Consider a ciphertext message consisting of 3 blocks of 64 bits each labeled c 1 , c 2 , c 3 : a. Show using a diagram, how the ciphertext would be decrypted if it had been encrypted using triple DES (EEE) with CBC on the outside and three different keys. b.
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This note was uploaded on 02/20/2012 for the course CNT 5412 taught by Professor Sudhir during the Spring '12 term at FSU.

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midterm1-sample-s12 - CNT 5412 Network Security (Partial)...

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