# Dat 2 - being B[8 2.4.4 Substitute the values found in the...

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1.2.3.3 Loop back to 1.2.3.1 until K[16] has been calculated. 2 Process a 64-bit data block. 2.1 Get a 64-bit data block. If the block is shorter than 64 bits, it should be padded as appropriate for the application. 2.2 Perform the following permutation on the data block. Initial Permutation (IP) 58 50 42 34 26 18 10 2 60 52 44 36 28 20 12 4 62 54 46 38 30 22 14 6 64 56 48 40 32 24 16 8 57 49 41 33 25 17 9 1 59 51 43 35 27 19 11 3 61 53 45 37 29 21 13 5 63 55 47 39 31 23 15 7 2.3 Split the block into two halves. The first 32 bits are called L[0], and the last 32 bits are called R[0]. 2.4 Apply the 16 subkeys to the data block. Start with i = 1. 2.4.1 Expand the 32-bit R[i-1] into 48 bits according to the bit-selection function below. Expansion (E) 32 1 2 3 4 5 4 5 6 7 8 9 8 9 10 11 12 13 12 13 14 15 16 17 16 17 18 19 20 21 20 21 22 23 24 25 24 25 26 27 28 29 28 29 30 31 32 1 2.4.2 Exclusive-or E(R[i-1]) with K[i]. 2.4.3 Break E(R[i-1]) xor K[i] into eight 6-bit blocks. Bits 1-6 are B[1], bits 7-12 are B[2], and so on with bits 43-48
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Unformatted text preview: being B[8]. 2.4.4 Substitute the values found in the S-boxes for all B[j]. Start with j = 1. All values in the S-boxes should be considered 4 bits wide. 2.4.4.1 Take the 1st and 6th bits of B[j] together as a 2-bit value (call it m) indicating the row in S[j] to look in for the substitution. 2.4.4.2 Take the 2nd through 5th bits of B[j] together as a 4-bit value (call it n) indicating the column in S[j] to find the substitution. 2.4.4.3 Replace B[j] with S[j][m][n]. Substitution Box 1 (S[1]) 14 4 13 1 2 15 11 8 3 10 6 12 5 9 0 7 0 15 7 4 14 2 13 1 10 6 12 11 9 5 3 8 4 1 14 8 13 6 2 11 15 12 9 7 3 10 5 0 15 12 8 2 4 9 1 7 5 11 3 14 10 0 6 13 S[2] 15 1 8 14 6 11 3 4 9 7 2 13 12 0 5 10 3 13 4 7 15 2 8 14 12 0 1 10 6 9 11 5 0 14 7 11 10 4 13 1 5 8 12 6 9 3 2 15 13 8 10 1 3 15 4 2 11 6 7 12 0 5 14 9 S[3] 10 0 9 14 6 3 15 5 1 13 12 7 11 4 2 8 13 7 0 9 3 4 6 10 2 8 5 14 12 11 15 1 13 6 4 9 8 15 3 0 11 1 2 12 5 10 14 7...
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## This note was uploaded on 02/26/2012 for the course MBA IT DOM1 taught by Professor Kviswanathan during the Spring '12 term at Indian Institute of Technology, Chennai.

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