In CEH v13 Module 14: Cryptography, IPSec (Internet Protocol Security) is defined as a framework used to establish secure communication channels over IP networks, particularly in VPNs.

IPSec supports encryption, authentication, and integrity.

Operates in Tunnel Mode (VPNs) or Transport Mode (End-to-End).

Core protocols: AH (Authentication Header) and ESP (Encapsulating Security Payload).

Option Analysis:

A. PEM: Privacy Enhanced Mail (email encryption).

B. PPP: Point-to-Point Protocol (data link layer, not encryption).

C. IPSEC: VPN encryption protocol.

D. SET: Secure Electronic Transaction (used in payment systems, obsolete).