计算机网络自顶向下方法(第4版)英文原版课件第八章.pptVIP

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 8: Network Security 8-* Authentication Header (AH) Protocol provides source authentication, data integrity, no confidentiality AH header inserted between IP header, data field. protocol field: 51 intermediate routers process datagrams as usual AH header includes: connection identifier authentication data: source- signed message digest calculated over original IP datagram. next header field: specifies type of data (e.g., TCP, UDP, ICMP) IP header data (e.g., TCP, UDP segment) AH header 8: Network Security 8-* ESP Protocol provides secrecy, host authentication, data integrity. data, ESP trailer encrypted. next header field is in ESP trailer. ESP authentication field is similar to AH authentication field. Protocol = 50. IP header TCP/UDP segment ESP header ESP trailer ESP authent. encrypted authenticated 8: Network Security 8-* Chapter 8 roadmap 8.1 What is network security? 8.2 Principles of cryptography 8.3 Message integrity 8.4 End point authentication 8.5 Securing e-mail 8.6 Securing TCP connections: SSL 8.7 Network layer security: IPsec 8.8 Securing wireless LANs 8.9 Operational security: firewalls and IDS 8: Network Security 8-* IEEE 802.11 security war-driving: drive around Bay area, see what 802.11 networks available? More than 9000 accessible from public roadways 85% use no encryption/authentication packet-sniffing and various attacks easy! securing 802.11 encryption, authentication first attempt at 802.11 security: Wired Equivalent Privacy (WEP): a failure current attempt: 802.11i 8: Network Security 8-* Wired Equivalent Privacy (WEP): authentication as in protocol ap4.0 host requests authentication from access point access point sends 128 bit nonce host encrypts nonce using shared symmetric key access point decrypts nonce, authenticates host no key distribution mechanism authentication: knowing the sh