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SSH is a common process allowing a shell (command interpreter) to be used over a secure connection. By safe, here, I mean that the connection is protected, authenticated and reliability tested. The encryption stops attackers studying the contents of the data being transmitted, the authorization allows both the client and the machine to be sure that they're connected to the other, and not for some intermediate system in a man-in-the-middle attack, and the integrity checking guarantees that the data is not being changed during transit. Together, these three functions provide a secure connection.
However, the password based login feature transmits your password through this link, to the remote server, where it is hashed and weighed against the stored value in the password file. To many, although the bond is encrypted, this isn't acceptable. SSH allows the utilization of public key authentication to login to a host. Here, you upload your public key to the host, and keep your private key on the client device, additionally password protected to ensure that no-one can steal your private key file and use access to be gained by it without a password.
Now, when the SSH relationship is established, the machine will have to check always the validation of the client; that's, make sure it's you signing in. This is formerly done by requesting your password, and comparing it contrary to the stored password hash. Now, the server encrypts a randomly generated token against your public key, and sends this for you. The private key associated with your public key, stored in a document to which only you've access, either by password defense, filesystem permissions and other means, may be the only key able to decrypt this message. Now, your SSH consumer will decrypt the message and send it back again to it is compared by the server, which from the original price. In reality, the certification is often also examined in the opposite direction, using the computers public key, which may be located by the customer. When the server knows you support the private key which corresponds to the public key, it grants you access.
So, you may ask, what's the security benefit here? Well, no secret information has been sent. You are no further transmitting a code, or are you transmitting all of your private key file. You're utilizing the keys to encrypt and decrypt an item of random data, which works one time only. Anyone who did somehow find a way to listen in with this data flow would not be able to restore entry by playing back your code, or even by playing back the same data transaction, as a different value would be secured the next time you login, and only the private key itself can decrypt that.
Public Key authentication is supported in OpenSSH, and also in PuTTY and a number of other SSH methods. Check your methods documentation for precisely just how to use public-key based logins. Forms Of Web Hosting Explained - TNZ2 Wiki
