Which protocol creates a secure and encrypted tunnel between two devices? (Port 500)

• A. Embedded System
• B. Web Service
• C. Internet Protocol Security (IPSec)
• D. Elliptic Curve Cryptography (ECC)

Answer: (C)

This question tests understanding of a protocol that creates a secure, encrypted tunnel between two devices, enabling private communication over an untrusted network. The protocol that fits this is Internet Protocol Security, or IPSec. IPSec works at the network layer to protect IP packets by authenticating and encrypting them as they travel between devices. It establishes security associations through a key exchange process that commonly uses port 500 (IKE), which sets up the tunnel’s cryptographic parameters. IPSec can operate in tunnel mode, wrapping the entire original IP packet inside a new envelope for VPN-style connections, providing confidentiality, integrity, and authentication for the whole communication path. It’s used in site-to-site VPNs and remote access VPNs to securely connect networks or devices over the internet.

Why the other options aren’t the right fit: an embedded system is a hardware/software platform, not a protocol for securing communications. a web service refers to an application-layer interface, not a protocol for creating encrypted tunnels. Elliptic Curve Cryptography is a type of public-key cryptography used within various protocols, not a tunnel protocol by itself.