Homework 1-Sp10

# Homework 1-Sp10 - CSE 794 Homework 1 Due: Monday, April 12...

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CSE 794 Homework 1 Due: Monday, April 12 by class time 1. Show that if an encryption scheme is perfectly secret and M K C  , then all ciphertexts have the same probability, i.e.,   1 Pr for all . || c c C C  2. For any fixed integer 0, n Vernam’s one-time pad over message space   0,1 n M can be described as follows. To encrypt a message   0,1 n m , one generates a key   0,1 n u k and encrypt as : m c m k  bit by bit. By Shannon’s Theorem, this scheme is perfectly secret for each n . Now, for a fixed 1, n consider Vernam’s one-time pad over message space   1 0,1 , n i i M the set of all strings of length . n To encrypt a message , mM we generate a key   0,1 (where | | denotes the length of ) m u k m m and encrypt as : m c m k bit by bit. Question: is this scheme perfectly secret?
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## This note was uploaded on 01/22/2011 for the course CSE 794 taught by Professor Tenh.lai during the Spring '10 term at Ohio State.

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