COMPUTER ETHICS AND SECURITY
CRYPTOGRAPHY AND ENCRYPTION
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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16×8
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12×8
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8×8
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4×8
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Detailed explanation-1: -Explanation: There are 64 bits to permute and this requires a 8×8 matrix.
Detailed explanation-2: -An initial permutation is required only once at the starting of the encryption process. In DES, after the complete plaintext is divided into blocks of 64 bits each, IP is required on each of them. This initial permutation is a phase in the transposition procedure.
Detailed explanation-3: -DES is a block cipher that operates on data blocks of 64 bits in size. DES uses a 64-bit key 8 × 8 including 1 bit for parity, so the actual key is 56 bits.
Detailed explanation-4: -Initial permutation Fixed, known mapping 64-64 bits. Key transformations Circular L shift of keys by A(i) bits in round (A(i) is known and fixed). Compression Permutation Fixed known subset of 56-bit input mapped onto 48-bit output.
Detailed explanation-5: -Explanation: The size of the key in the SDES algorithm is 10 bits.