What is key-based authentication in Linux?

Key-based authentication is a kind of authentication that may be used as an alternative to password authentication. Instead of requiring a user’s password, it is possible to confirm the client’s identity by using asymmetric cryptography algorithms, with public and private keys.

How do I set up key-based authentication?

Procedure

1. Use the ssh-keygen tool to create a key pair.
2. Validate that the keys were generated.
3. Enable key-based authentication in the /etc/ssh directory on the SSH server.
4. Copy the rsa.
5. If you have an existing authorized_keys file, edit it to remove any no-pty restrictions.

What is key-based authentication?

Key-Based Authentication Overview In case you aren’t already familiar with key-based authentication, it is a way of authenticating to remote servers without using a password. Instead, a private key stored on the client is paired with a public key stored on the server.

How does key-based authentication work?

The most common means of authentication is via SSH asymmetric key pairs. The server uses the public key to encrypt a message and send it to the client. If the client has the correct private key, they can decrypt the message and send it back to the server for verification.

How does SSH private key authentication work?

The SSH key pair is used to authenticate the identity of a user or process that wants to access a remote system using the SSH protocol. The SSH client then decrypts the challenge message and responds back to the SSH server. The user or process must respond correctly to the challenge to be granted access.

How to configure SSH key-based authentication on a Linux server?

For this method to work, you must already have password-based SSH access to your server. To use the utility, you simply need to specify the remote host that you would like to connect to and the user account that you have password SSH access to. This is the account where your public SSH key will be copied. You may see a message like this:

How to enable password based authentication on Your Linux server?

The server must also have password authentication enabled. If you are logged in as a non root user, you may run sudo -i to switch to root user or you may use sudo command before all the commands. If you are on a Linux client machine you will need to install openssh-client onto your machine.

How to create SSH key pair on local computer?

How To Create SSH Keys. The first step to configure SSH key authentication to your server is to generate an SSH key pair on your local computer. To do this, we can use a special utility called ssh-keygen, which is included with the standard OpenSSH suite of tools.

How is the passphrase used in SSH authentication?

The passphrase is only used to decrypt the key on the local machine. This means that network-based brute forcing will not be possible against the passphrase. The private key is kept within a restricted directory. The SSH client will not recognize private keys that are not kept in restricted directories.