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Unformatted text preview: Note that K3 will be the key stream for encryption. cipher text = (data ) XOR (key). The random sequence generator’s initial state is the XOR result of two fourbit vectors: IV (initial vector) and KV (key vector). That is, Initial State = IV xor KV IV will be selected by the transmitter and will be sent to the receiver with the cipher text as shown below: IV (four bits, unencrypted) + cipher text KV, also a fourbit vector, is the shared key between the sender and the receiver. KV must be kept secrete. Otherwise, the encryption algorithm will be compromised. (a)What is the problem if we only use IV, but not KV to set the initial state? (b) What is the problem if we only use KV to set the initial state? (c) Assume IV= [1110] and at time = 0, KV = [1101]. Determine the cipher text for the following plain text (the rightmost bit is sent in first for encryption at t=0) 1010 0111 D Q D Q D Q D Q XOR K0 K1 K2 K3...
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 Spring '11
 Prof.ShenghuiSong
 Cryptography, Encryption, Plaintext

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