CRIPTOGRAFIA - FESP

Putting it all together: Building a
real VPN
With coverage of the Authenticating Header and Encapsulating Security Payload
complete, we're ready to enable both encryption and authentication to build a
real VPN. The whole purpose of a Virtual Private Network is to join two trusted
networks across an untrusted intermediate network, as is by stringing a very
long Ethernet cable between the two. This is commonly used to connect branch
offices with company headquarters, allowing all users to share sensitive
resources without fear of interception.
Clearly, a secure VPN requires both authentication and encryption. We know
that ESP is the only way to provide encryption, but ESP and AH both can provide
authentication: which one do we use?