How to encrypt a package in C/C++?

Question

C++ / C#

Good day.
There are two machines connected via a router.
The task is to write a driver that establishes a connection, key exchange and encryption of all packets between machines.
Tell me which way to drip, at what OSI level to do it.

Answer 1

There are two machines connected via a router.
write a driver that establishes a connection, key exchange and encryption of all packets between machines

Read about IPsec . No driver needed.
IPsec operates at the network (3rd) layer.