Host authentication

By name or address

DNS name, IP address, MAC address, and others.

Extremely weak, no cryptographic proofs.

• Nevertheless, used by many services.

• e.g. NFS, TCP wrappers.

With cryptographic keys

Keys shared among peers.

• With a history of usual interaction.

Per-host asymmetric key pair.

• Pre-shared public keys with usual peers.

• Certified public keys with any peer.