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

IPsec (Internet Protocol Security) operates at Layer 3 and provides two core protocols - AH (Authentication Header) for integrity and ESP (Encapsulating Security Payload) for encryption - along with IKE for key negotiation. It is the foundational technology used in site-to-site and remote-access VPNs to establish secured channels between two endpoints.

PEM (Privacy Enhanced Mail) is a Base64-encoded file format used to store cryptographic objects such as certificates and keys, not a protocol for establishing secure communication channels.

SET (Secure Electronic Transaction) was a protocol developed by Visa and Mastercard for securing credit card transactions over the internet and is unrelated to VPN tunnel establishment.

PPP (Point-to-Point Protocol) is a Layer 2 data-link protocol used to encapsulate network-layer packets over serial connections and does not provide encryption or authentication by itself.