1 / 41

Information Security Principles

University of Palestine. Information Security Principles. ITGD 2202. DES. Data Encryption Standard. Overview of the DES Generation of Round Keys Encipherment DES Modes. Overview of the DES. A block cipher: encrypts blocks of 64 bits using a 64 bit key outputs 64 bits of ciphertext

wyatt-castro
Download Presentation

Information Security Principles

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. University of Palestine Information Security Principles ITGD 2202 DES Eng. Mohammed abulamddi

  2. Data Encryption Standard • Overview of the DES • Generation of Round Keys • Encipherment • DES Modes Eng. Mohammed abulamddi

  3. Overview of the DES • A block cipher: • encrypts blocks of 64 bits using a 64 bit key • outputs 64 bits of ciphertext • A product cipher • basic unit is the bit • performs both substitution and transposition (permutation) on the bits • Cipher consists of 16 rounds (iterations) each with a round key generated from the user-supplied key Eng. Mohammed abulamddi

  4. Overview of the DES Eng. Mohammed abulamddi

  5. Generation of Round Keys • Round keys are 48 bits each Eng. Mohammed abulamddi

  6. PC-1 PC-2 Eng. Mohammed abulamddi

  7. Eng. Mohammed abulamddi

  8. LSH Eng. Mohammed abulamddi

  9. LSHBefore After Eng. Mohammed abulamddi

  10. PC-2 Eng. Mohammed abulamddi

  11. Encipherment Eng. Mohammed abulamddi

  12. 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 IP-1 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 Eng. Mohammed abulamddi

  13. The f Function Eng. Mohammed abulamddi

  14. E BIT-SELECTION TABLE 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 P 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 S1 Column Number Row No.0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 0 14 4 13 1 2 15 11 8 3 10 6 12 5 9 0 7 1 0 15 7 4 14 2 13 1 10 6 12 11 9 5 3 8 2 4 1 14 8 13 6 2 11 15 12 9 7 3 10 5 0 3 15 12 8 2 4 9 1 7 5 11 3 14 10 0 6 13 Eng. Mohammed abulamddi

  15. DES Modes • Electronic Code Book Mode (ECB) • Encipher each block independently • Cipher Block Chaining Mode (CBC) • Xor each block with previous ciphertext block • Requires an initialization vector for the first one • Encrypt-Decrypt-Encrypt Mode (2 keys: k, k) • c = DESk(DESk–1(DESk(m))) • Encrypt-Encrypt-Encrypt Mode (3 keys: k, k, k) • c = DESk(DESk(DESk(m))) Eng. Mohammed abulamddi

  16. Example Eng. Mohammed abulamddi

  17. Eng. Mohammed abulamddi

  18. Eng. Mohammed abulamddi

  19. Eng. Mohammed abulamddi

  20. Eng. Mohammed abulamddi

  21. Eng. Mohammed abulamddi

  22. Eng. Mohammed abulamddi

  23. Before 16 After 16 Eng. Mohammed abulamddi

  24. Eng. Mohammed abulamddi

  25. Eng. Mohammed abulamddi

  26. Eng. Mohammed abulamddi

  27. Feistel scheme Eng. Mohammed abulamddi

  28. Eng. Mohammed abulamddi

  29. Eng. Mohammed abulamddi

  30. Eng. Mohammed abulamddi

  31. Eng. Mohammed abulamddi

  32. Eng. Mohammed abulamddi

  33. Eng. Mohammed abulamddi

  34. Eng. Mohammed abulamddi

  35. Eng. Mohammed abulamddi

  36. Eng. Mohammed abulamddi

  37. Eng. Mohammed abulamddi

  38. Eng. Mohammed abulamddi

  39. Eng. Mohammed abulamddi

  40. Eng. Mohammed abulamddi

  41. Q ? Eng. Mohammed abulamddi

More Related