An SSH key has two components:
- A public key that is available for all (the client and the server). It is a cryptographic key that can be obtained and used by anyone to encrypt messages intended for a particular recipient. The server uses it for authentication.
- A private key (kept secret). It is known only by the client and is kept on their machine. The private key is used for deciphering messages with the corresponding public key.
Using an SSH key to create a connection between two computers offers the advantage that only the public key needs to be exchanged on the network. Since transmissions encrypted with a public key can only be deciphered with the corresponding private key and a password, a pirate cannot do anything to decipher communications on the Web, as they have no access to the private key.