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SYMMETRIC CRYPTOSYSTEMS Symmetric Cryptosystems 10/06/2015 | pag. 2.

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Presentation on theme: "SYMMETRIC CRYPTOSYSTEMS Symmetric Cryptosystems 10/06/2015 | pag. 2."— Presentation transcript:

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2 SYMMETRIC CRYPTOSYSTEMS Symmetric Cryptosystems 10/06/2015 | pag. 2

3 Block Ciphers: Classical examples Symmetric Cryptosystems 10/06/2015 | pag. 3 Affine Cipher Affine Linear and Linear Cipher Vigenère Hill We needed some linear algebra!

4 Affine Cipher Symmetric Cryptosystems 10/06/2015 | pag. 4

5 Example: Cryptanalysis of the Affine Cipher Symmetric Cryptosystems 10/06/2015 | pag. 5

6 Intermezzo: Matrices over Rings Cryptography 10/06/2015 | pag. 6

7 Intermezzo: Invertible Matrices Cryptography 10/06/2015 | pag. 7

8 Intermezzo: Invertible Matrices Cryptography 10/06/2015 | pag. 8

9 Intermezzo: Invertible Matrices Cryptography 10/06/2015 | pag. 9

10 Intermezzo: Invertible Matrices Cryptography 10/06/2015 | pag. 10

11 Intermezzo: Affine Linear Functions Cryptography 10/06/2015 | pag. 11

12 Intermezzo: Affine Linear Functions Cryptography 10/06/2015 | pag. 12

13 Affine Linear Cipher Cryptography 10/06/2015 | pag. 13

14 Affine Linear Cipher Cryptography 10/06/2015 | pag. 14

15 Example: Affine Linear Cipher - Vigenère Cryptography 10/06/2015 | pag. 15

16 Example: Linear Cipher - Hill Cryptography 10/06/2015 | pag. 16

17 Example: Linear Cipher – Permutation Cipher Cryptography 10/06/2015 | pag. 17

18 Cryptanalysis of the Affine Linear Cipher Symmetric Cryptosystems 10/06/2015 | pag. 18

19 Cryptanalysis of the Affine Linear Cipher Symmetric Cryptosystems 10/06/2015 | pag. 19

20 Cryptanalysis of the Affine Linear Cipher Symmetric Cryptosystems 10/06/2015 | pag. 20

21 Example: Cryptanalysis of the Affine Linear Cipher Symmetric Cryptosystems 10/06/2015 | pag. 21 FUSS.

22 Block Ciphers: Remark Secure block ciphers must not be (affine) linear or easy to approximate by linear functions!!! Cryptography 10/06/2015 | pag. 22

23 Block Ciphers: Remark Cryptography 10/06/2015 | pag. 23 Implementation of a (non-linear!) substitution in a block cipher often occurs through a look-up table, called S-box.

24 Block Ciphers: Advanced examples Symmetric Cryptosystems 10/06/2015 | pag. 24 DES – Feistel Cipher AES – Rijndael

25 DES Cryptography 10/06/2015 | pag. 25

26 DES: Feistel Cipher Cryptography 10/06/2015 | pag. 26 An iterated block cipher is a block cipher involving the sequential repetition of an internal function called rounds. (iterated)

27 DES: Feistel Cipher Cryptography 10/06/2015 | pag. 27

28 DES: Feistel Cipher Cryptography 10/06/2015 | pag. 28

29 DES: Algorithm Cryptography 10/06/2015 | pag. 29

30 DES: Algorithm Cryptography 10/06/2015 | pag. 30

31 DES: Algorithm Cryptography 10/06/2015 | pag. 31

32 DES: Algorithm Cryptography 10/06/2015 | pag. 32

33 DES: Algorithm Cryptography 10/06/2015 | pag. 33

34 DES: Algorithm Cryptography 10/06/2015 | pag. 34

35 DES: Algorithm Cryptography 10/06/2015 | pag. 35

36 DES: Algorithm Cryptography 10/06/2015 | pag. 36

37 DES: Algorithm Cryptography 10/06/2015 | pag. 37

38 DES: S-Boxes Cryptography 10/06/2015 | pag. 38

39 DES: Algorithm Cryptography 10/06/2015 | pag. 39

40 DES: Algorithm Cryptography 10/06/2015 | pag. 40

41 DES: Algorithm Cryptography 10/06/2015 | pag. 41

42 DES: Algorithm Cryptography 10/06/2015 | pag. 42 Round number Number of left rotations 11 21 32 42 52 62 72 82 91 102 112 122 132 142 152 161

43 DES: Algorithm Cryptography 10/06/2015 | pag. 43

44 DES: Algorithm Cryptography 10/06/2015 | pag. 44

45 DES: Algorithm Cryptography 10/06/2015 | pag. 45

46 Example: DES Key Cryptography 10/06/2015 | pag. 46 Conversion Code - Chart DECI MAL 0123456789101112131415 HEX0123456789ABCDEF BINA RY 0000000100100011010001010110011110001001101010111100110111101111

47 Example: S-Box Cryptography 10/06/2015 | pag. 47

48 Example: DES Cryptography 10/06/2015 | pag. 48

49 Example: DES Cryptography 10/06/2015 | pag. 49

50 Example: DES Cryptography 10/06/2015 | pag. 50

51 Example: DES Cryptography 10/06/2015 | pag. 51


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