Which protocol is used for setting up secured channels between two devices, typically in VPNs?

IPSec (Internet Protocol Security) operates at the network layer and provides two core protocols - AH (Authentication Header) for integrity and ESP (Encapsulating Security Payload) for encryption - to establish secured channels between devices. It uses IKE (Internet Key Exchange) to negotiate and set up security associations, which is why it is the primary protocol used in site-to-site and remote-access VPNs.

PEM (Privacy Enhanced Mail) is a Base64-encoded certificate and key file format, not a protocol for establishing secure communication channels.

SET (Secure Electronic Transaction) is a protocol designed specifically for securing credit card transactions, not general-purpose VPN tunnels.

PPP (Point-to-Point Protocol) is a data link layer protocol for direct connections between two nodes but does not provide encryption or authentication for secured VPN channels.