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

PPP (Point-to-Point Protocol) is a data link layer encapsulation protocol for direct two-node connections and does not provide encryption or secure channel negotiation.

IPSec (Internet Protocol Security) operates at the network layer and provides confidentiality, integrity, and authentication via two protocols - AH (Authentication Header) and ESP (Encapsulating Security Payload). It negotiates secure channels using IKE (Internet Key Exchange) and is the dominant standard for 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) was a protocol designed specifically for securing credit card transactions over the internet, not for general VPN channel setup.