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Unformatted text preview: or not, and prove your answer . In each case, say what the space C oF the ciphertexts is, and note the sizes oF the message space M and key space K . Do these sizes correlate somehow with whether or not the cipher is secure? Can you explain why? 1. Let M = S and K = { , 1 } 2 , i.e. both the message and the key are (2 )long bit strings 1 However, not every (2 )bit string can be a valid message. or example, For = 3, we could have m = [00 , 01 , 00] = 000100 but m = [11 , 00 , 11] = 110011 is not in M because 11 n S . 2. Let M = { , 1 } 2 and K = S 3. Let M = K = S . [[Hint: This one is actually not perfectly secure. ..]] 1 We use notation A n to denote a set of nlong sequences [ A 1 , A 2 , ..., A n ] where each A i is an element of A . Using this notation, { , 1 } n denotes a set of all nlong binary strings. H11...
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This homework help was uploaded on 01/30/2008 for the course ICS 180 taught by Professor Jarecki during the Spring '04 term at UC Irvine.
 Spring '04
 Jarecki

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