Ch 29

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Ch 29

  1. 1. Security PART VII
  2. 2. Security Topics
  3. 3. Chapters Chapter 29 Cryptography Chapter 30 Message Authentication, User Authentication, and Key Management Chapter 31 Security Protocols in The Internet
  4. 4. Chapter 29 Cryptography
  5. 5. 29.1 Introduction Introduction to Cryptography
  6. 6. Figure 29.1 Cryptography components
  7. 7. Figure 29.2 Encryption and decryption
  8. 8. In cryptography, the encryption/decryption algorithms are public; the keys are secret. Note :
  9. 9. 29.2 Symmetric-Key Cryptography Traditional Cipher Block Cipher Operation Modes
  10. 10. Figure 29.3 Symmetric-key cryptography
  11. 11. In symmetric-key cryptography, the same key is used by the sender (for encryption) and the receiver (for decryption). The key is shared. Note :
  12. 12. In symmetric-key cryptography, the same key is used in both directions. Note :
  13. 13. Symmetric-key cryptography is often used for long messages. Note :
  14. 14. Figure 29.4 Caesar cipher
  15. 15. Figure 29.5 Example of monoalphabetic substitution
  16. 16. In monoalphabetic substitution, the relationship between a character in the plaintext to the character in the ciphertext is always one-to-one. Note :
  17. 17. Figure 29.6 Vigenere cipher
  18. 18. In polyalphabetic substitution, the relationship between a character in the plaintext and a character in the ciphertext is one-to-many. Note :
  19. 19. Figure 29.7 Transpositional cipher
  20. 20. Figure 29.8 Block cipher
  21. 21. Figure 29.9 P-box
  22. 22. Figure 29.10 S-box
  23. 23. Figure 29.11 Product block
  24. 24. Figure 29.12 DES
  25. 25. Figure 29.13 General scheme of DES
  26. 26. Figure 29.14 Iteration block
  27. 27. Figure 29.15 Triple DES
  28. 28. The DES cipher uses the same concept as the Caesar cipher, but the encryption/decryption algorithm is much more complex due to the sixteen 48-bit keys derived from a 56-bit key. Note :
  29. 29. Figure 29.16 ECB mode
  30. 30. Figure 29.17 CBC mode
  31. 31. Figure 29.18 CFM
  32. 32. Figure 29.19 CSM
  33. 33. 29.3 Public-Key Cryptography RSA Choosing Public and Private Keys
  34. 34. Figure 29.20 Public-key cryptography
  35. 35. Public-key algorithms are more efficient for short messages. Note :
  36. 36. Figure 29.21 RSA

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