Implementing Virtual Private Networks

Implementing Virtual Private Networks

1. VPN Terminology

   • Cryptosystem
   • Encryption/Decryption
     • Encryption transforms information (clear text) into ciphertext which is not readable by unauthorized users.
   • Authentication/Hashing
     • Guarantees message integrity by using an algorithm to convert a variable length message and shared secret key into a single fixed-length string.
   • Non-repudiation
     • Is the ability to prove a transaction occurred
   • Pre-shared key
     • Identifies a communicating party during a phase 1 IKE negotiation.
   • Internet Protocol Security
     • Authentication header
     • Encapsulating Security Payload
   • Crypto Map

2. VPNs

   • Conventional Private Networks
   • Virtual Private Networks
   • VPN Packet Encapsulation

3. VPN Topologies

   • Site-to-Site
   • Remote Access

4. Key Exchange

   • Negotiates key exchange parameters (IKE).
     • Establishes a shared key (DH).
       • Authenticates the peer.
         • Negotiates the encryption parameters.

5. GRE Tunnel

   • Cisco Generic Routing Encapsulation (GRE)
     • IP Security Protocol (IPsec)
       • Does not support multicast
     • Does not provide encryption

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