The document provides an overview of cryptography and network security, covering topics including symmetric and asymmetric cryptography, key management, hashing algorithms, and digital signatures. It discusses various encryption algorithms such as DES, AES, RSA, and the principles of secure communications and authentication protocols. Key security trends and challenges, including key distribution and digital signatures, as well as real-world applications like SSL/TLS and PKI are also addressed.

1. Cryptography and Network SecurityAn OverviewNagendra U Mnamahesh@cisco.com

2. AgendaIntroduction

3. Security Trends

4. ASM: Attacks, Services, Mechanisms

5. A Network Security Model

6. Private-Key Cryptography / Symmetric Ciphers

7. DES, 3DES, AES

8. Private Key Distribution

9. Public-Key Cryptography

10. Mathematical Concepts

11. The RSA Algorithm

12. Key Management

13. Hashing Algorithms

14. Digital Signatures

15. Authentication Protocols

16. Network Security

17. X.509, Public Key Infrastructure (PKI)

18. PGP, S/MIME

19. SSL/TLS

20. IPSec

23. Model for Network Security

24. Simplified Model of Conventional EncryptionModel of Conventional Cryptosystem

25. Goals of an ‘Unconditionally Secure’ Encryption Algorithm:● The cost of breaking the cipher exceeds the value of the encrypted information.● The time required to break the cipher exceeds the useful lifetime of the information.CLASSIC SUBSTITUTION ALGORITHMS:Caesar Cipher:C = E(k, p) = (p + k) mod 26p = D(k, C) = (C - k) mod 26where K={1..25} for englishMonoalphabetic Ciphers:Substitute one arbitrary alphabet in the place of a particular alphabetFor english, it generates a key space of 26! (~4 x 10^26) keysBUT it can be broken by exploiting patterns in languagePolyalphabetic Ciphers:Use different monoalphabetic substitutions as one proceeds through the plaintext message.Vignere Cipher

26. CLASSIC TRANSPOSITION ALGORITHMS:Rail-fence Technique:Written as a sequence of diagonals and read off as a sequence of rowsEg: “CiscoSystems” is written asC s o y t mi c S s e sCipherText:CsoytmicSsesA more complex scheme is to write the message in a rectangle, row by row, and read the message off, column by column, but permute the order of the columns. The order of the columns then becomes the key to the algorithm.Rotor Machines:Steganography:Strictly speaking, its NOT encryptionConceal the existence of a messageJPEG steganography