How to make Virtual Network Private?

How to make Virtual Network Private?  The VPN traffic between two branches is locked with special keys, and only computers or persons owning this key can open this lock and look at the data sent.[3]  All data sent from Singapore to Seoul or from Seoul to Singapore must be encrypted before and decrypted after transmission.  The encryption safeguards the data in the connection like the walls of the tunnel protect the train from the mountain around it.This explains why Virtual Private Networks are often simply known as tunnels or VPN tunnels, and the technology is often called tunneling-even if there is no quantum mechanics involved [4]  The exact method of encryption and providing the keys to all parties involved makes one of the main distinguishing factors between different VPN solutions.