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

PEM (Privacy Enhanced Mail) is an outdated standard for securing email communications and is not used for setting up general secure channels in VPNs.

PPP (Point-to-Point Protocol) is a data link layer protocol used for direct connections, but it does not inherently provide robust encryption and authentication for secure IP-based channels; it often relies on other protocols or extensions like PPTP (which uses PPP) for security in VPNs.

IPsec (Internet Protocol Security) is a suite of protocols that provides cryptographic security services at the IP layer, including authentication and encryption for IP packets. It is widely recognized and utilized for establishing secure communication tunnels, such as those found in Virtual Private Networks (VPNs), to protect data integrity and confidentiality between devices or networks.

SET (Secure Electronic Transaction) is a protocol designed specifically for securing credit card transactions over open networks, primarily in e-commerce, and is not a general-purpose protocol for creating secure communication channels like IPsec in VPNs.