1. Virtual Private Network (VPN)
 secure tunnel over insecure public channel
 authenticated transmission
 host to host transmission is typical
 service independent
WHAT IS NEEDED?
VPN appliances
Knowledge of IP subnets
Agreed-upon authentication
Agreed-upon encryption algorithms

2. Cisco VPN Cisco supports an IPSec version of VPN
Diffie-Hellman is used to exchange keys.
3DES or AES is used for channel.
VPN connects two routers/firewalls.
Transmission:
Other standards
Point To Point Tunneling Protocol (PPTP)
Layer 2 Tunneling Protocol (L2TP)

3. Pros & Cons Advantages Authenticity & confidentiality
Even source/dest IDs are confidential
Disadvantages

4. Secure Socket Layer (SSL)
 developed by Netscape
 used by web browsers for secure interchange
 communicates above layer 4 using sockets
 simplified protocol
1) Client connects to web server via SSL (https)
2) Server returns digital certificate (public key)
3) Client browser authenticates certificate from list of
trusted sites
4) Client sends E( SessionKey, ServerPubKey )
5) Server extracts session key and verifies correct receipt
6) Session key used to support https exchange
via selected algorithm (DES, IDEA, etc.)