8.1 Security Goals — The CIA Triad
The foundation of all network information security is structured around the three core objectives of the CIA Triad.
Figure 8.1: The CIA Triad: Confidentiality (only authorized eyes), Integrity (tamper-proof), and Availability (uninterrupted uptime).
8.2 Encryption Techniques (Symmetric vs Asymmetric)
Cryptography converts plain readable text into unreadable ciphertext to guarantee confidentiality across open networks.
Figure 8.2: Symmetric encryption uses one shared secret key; Asymmetric uses a mathematically linked public-private keypair.
8.3 Perimeter Defense: Firewalls and Virtual Private Networks (VPNs)
Enterprise perimeters are fortified using Firewalls to inspect traffic rules and Virtual Private Networks (VPNs) to tunnel encrypted packets across unsecure public networks.
Figure 8.3: A Firewall blocks unauthorized ports at the boundary, while a VPN creates an end-to-end encrypted tunnel across the public Internet.
