chapter3-2 - 1 Secret cryptosystem--DES • Data Encryption...

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Unformatted text preview: 1 Secret cryptosystem--DES • Data Encryption Standard (DES) • First version in 1975, developed by IBM • A type of iterated cipher • Plaintext block: 64 bits, key: 56 bits, ciphertext block:64 bits • Steps: – Initial permutation (IP) – 16 rounds of encryption – Inverse permutation (IP-1 ) 2 IP L R R 1 = L 0 f ( R , K 1 ) L 1 = R R 2 = L 1 f ( R 1 , K 2 ) L 2 = R 1 R 1 5 = L 1 4 f ( R 1 4 , K 1 5 ) L 1 5 = R 1 4 R 1 6 = L 1 5 f ( R 1 5 , K 1 6 ) L 1 6 = R 1 5 6 4 3 2 3 2 K 1 K 2 K 1 6 f 4 8 3 2 f f IP- 1 o u tp u t T DES—encryption process 3 DES—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 40 8 48 16 56 24 64 32 39 7 47 15 55 23 63 31 38 6 46 14 54 22 62 30 37 5 45 13 53 21 61 29 36 4 44 12 52 20 60 28 35 3 43 11 51 19 59 27 34 2 42 10 50 18 58 26 33 1 41 9 49 17 57 25 IP IP-1 4 DES—each iteration L i =R i-1 , R i =L i-1  f(R i-1 ,K i ) L i-1 R i-1 L i R i f K i 5 DES— f function E extension P permutation 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 16 7 20 21 29 12 28 17 1 15 23 26 5 18 31 10 2 8 24 14 32 27 3 9 19 13 30 6 22 11 4 25 6 DES— S boxes For each S box: 6 bits  4 bits. A S box is a 4  16 array: 6 bits ( b 1 b 2 b 3 b 4 b 5 b 6 ) are divided into 2-bit ( b 1 b 6 ) row number, 4-bit ( b 2 b 3 b 4 b 5 ) column number, the output is the value corresponding to the (row, column) value, which is from 0 to 15 (4 bits). S1 box: S2 box: 14 4 13 1 2 15 11 8 3 10 6 12 5 9 7 15 7 4 14 2 13 1 10 6 12 11 6 5 3 8 4 1 14 8 13 6 2 11 15 12 9 7 3 10 5 15 12 8 2 4 9 1 7 5 11 3 14 10 6 13 15 1 8 14 6 11 3 4 9 7 2 13 12 5 10 3 13 4 7 15 2 8 14 12 1 10 6 9 11 5 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 5 14 9 7 10 9 14 6 3 15 5 1 13 12 7 11 4 2 8 13 7 9 3 4 6 10 2 8 5 14 12 11 15 1 13 6 4 9 8 15 3 11 1 2 12 5 10 14 7 1 10 13 6 9 8 7 4 15 14 3 11 5 2 12 7 13 14 3 6 9 10 1 2 8 5 11 12 4 15 13 8 11 5 6 15 3 14 7 2 12 1 10 14 9 10 6 9 12 11 7 13 15 1 3 14 5 2 8 4 3 15 6 10 1 13 8 9 4 5 11 12 7 2 14 S3 box: S4 box: S5 box: 2 12 4 1 7 10 11 6 8 5 3 15 13 14 9 14 11 2 12 4 7 13 1 5 15 10 3 9 8 6 4 2 1 11 10 13 7 8 15 9 12 5 6 3 14 11 8 12 7 1 14 2 13 6 15 9 10 4 5 3 8 S8 box: S7 box: S6 box: 12 1 10 15 9 2 6 8 13 3 4 14 7 5 11 10 15 4 2 7 12 9 5 6 1 13 14 11 3 8 9 14 15 5 2 8 12 3 7 4 10 1 13 11 6 4 3 2 12 9 5 15 10 11 14 1 7 6 8 13 4 11 2 14 15 8 13 3 12 9 7 5 10 6 1 13 11 7 4 9 1 10 14 3 5 12 2 15 8 6 1 4 11 13 12 3 7 14 10 15 6 8 5 9 2 6 11 13 8 1 4 10 7 9 5 15 14 2 3 12 13 2 8 4 6 15 11 1 10 9 3 14 5 12 7 1 15 13 8 10 3 7 4 12 5 6 11 14 9 2 7 11 4 1 9 12 14 2 6 10 13 15 3 5 8 2 1 14 7 4 10 8 13 15 12 9 3 5 6 11 9 DES— computation of key schedule C D LS 1 LS 1 LS 2 LS 2 C 1 D 1 PC-2 K 1 LS 16 LS 16 C 16 D 16 PC-2 K 16 PC-1 K (64 bits) Actual key is 64 bits, of which 56...
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This note was uploaded on 12/25/2010 for the course ALL 0204 taught by Professor 79979 during the Spring '10 term at National Chiao Tung University.

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chapter3-2 - 1 Secret cryptosystem--DES • Data Encryption...

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