The same has to occur when users and computers need access to other computers. The mechanism to control this node-node access is implemented via the ssh protocole.
The ssh protocole is the software suite that administers access to a user on another computer on an internet channel. To make this access easier the ssh protole provides a mean to accept identification of a user and of a pairs of computers based on secure, encrypted information sufficient to positively identify user and computers. This relies on efficient and secure encryption protocol.
This link ssh -keygen explains the steps needed to establish encrypted keys which are used to mathematically identify users and computers.