1. Cryptography Chapter 7 Part 2 Pages 781 to 812

2. Symmetric Cryptography Secret Key Figure 7-10 on page 782 Key distribution problem – Secure courier Many keys – N(N-1)/2 – N=100, 4,950 keys

3. Symmetric Cryptography Provides only confidentiality Very fast. Hard to break. Data Encryption Standard (DES) Triple-DES (3DES) Advanced Encryption Standard (AES)

4. Asymetric Cryptography Public Key/Private Key Figure 7-11 on page 784 Alice, Bob, and Evil Eve Very slow Manageable key distribution Authentication and Non-repudiation – Bob encrypts with his private key

5. Asymetric Cryptography Bob sends message to Alice S= Private[Bob](Public[Alice]){Message} Alice authenticates that it came from Bob A = Public[Bob]{S} Alice decrypt – confidentiality M = Private[Alice]{A}

6. Asymetric Cryptography Rivest-Shamir-Adleman (RSA) Elliptic curve cryptosystem (ECC)

7. Comparison Table 7-1 on page 786

8. Block Ciphers 32, 64, or 128 bit blocks Figure on page 787 Confusion – substitution Diffusion – transposition Avalanche effect – slight change to input causes significant change to output IV – initialization vector – Don’t get same result

9. Stream Cipher Figure 7-13 on page 789 Figure 7-14 on page 790 Streaming communications – such as VoIP

10. Hybrid Encryption Figure page 794

11. Session Keys Figure 7-16 on page 797

12. DES Data Encryption Standard Data Encryption Algorithm (DEA) 56-bit keys 64-bit blocks 16 rounds of transpositions and substitution functions

13. DES ANSI (American National Standards Institute) standard in 1978 1998: Electronic Frontier Foundation broke DES in 3 days with brute force attack against keyspace using 1,536 microprocessors

14. DES Modes Electronic Code Book (EBC) 64-bit block encrypted by the key Can be done in parallel Can disclose patterns

15. Cipher Block Chaining (CBC) Figure 7-17 IV – 64-bit initialization vector Previous Ciphtertest XOR next Plaintext Errors persist

16. Cipher Feedback (FRB) Mode Figure 7-18 on page 805 For small text such as keystrokes or mouse movements Plaintext XOR Keystream

17. Output Feedback (OFB) Mode Figure 7-19 on page 806 Errors in data do not persist For video or VoIP

18. Counter (CTR) Mode Figure page 807 No IV Can encrypt in parallel

19. Triple DES DES-EEE3 DES-EDE2 48 rounds is slow Used while NIST adopted a new standard

20. AES Advanced Encryption Standard Rijndael Block & Key lengths: 128, 192, 256 NIST standard