Public-Key SSH Login

SSH is a popular system allowing a remote shell (command interpreter) to be used over a secure connection. By secure, here, I mean that the connection is encrypted, authenticated and integrity checked. The encryption prevents attackers reading the contents of the data being transmitted, the authentication allows both the client and the server to be sure that they are connected to the other, and not to some intermediate system in a man-in-the-middle attack, and the integrity checking ensures that the data is not being changed during transit. Together, these three features provide a secure connection.

Even so, the password based login feature transmits your password through this link, to the remote server, where it is hashed and compared with the stored value in the password file. To many, even though the connection is encrypted, this is not satisfactory. SSH allows the use of public key authentication to login to a server. Here, you upload your public key to the server, and keep your private key on the client machine, optionally password protected so that no one can steal your private key file and use it to gain access without a password.

Now, when the SSH...