Using an SSH public key provides a secure and convenient way to authenticate yourself to remote servers. Here’s a guide on how to set up and use SSH public key authentication:

Generate SSH Key Pair:

First, generate a key pair consisting of a public key and a private key. The private key should be kept secure on your local machine, while the public key can be shared with the remote server.

ssh-keygen -t rsa -b 4096 -C "your_email@example.com"

Copy Public Key to Server:

To use your SSH public key for secure authentication on your server, copy the contents of your SSH public key file (usually ~/.ssh/id_rsa.pub or ~/.ssh/id_ed25519.pub) by running cat ~/.ssh/id_rsa.pub or cat ~/.ssh/id_ed25519.pub in your terminal. Then, go to your web hosting provider’s website, navigate to the Advanced or SSH Key section, and paste the copied key. This allows the server to verify your identity using your public key.

cat ~/.ssh/id_rsa.pub | pbcopy

Authenticate with Private Key:

When you attempt to connect to the remote server using SSH, your local SSH client presents your private key to the server. The server verifies your identity by checking if the public key stored in authorized_keys matches the one presented by your client.

ssh user@remote_server

How SSH Key Authentication Works

• Generate SSH Key Pair: When you generate an SSH key pair, you create a private key and a corresponding public key. The private key is kept secure on your local machine, while the public key is shared with the remote server.
• Copy Public Key to Server: The public key is added to the ~/.ssh/authorized_keys file on the remote server. This file contains a list of all public keys that are authorized to access the server.
• Authenticate with Private Key: During authentication, the server checks the public key in the authorized_keys file and sends a challenge to the client, which the client can only decrypt if it has the corresponding private key. If the client successfully decrypts the challenge, the server grants access.

Benefits of SSH Key Authentication

• Enhanced Security: Since the private key is never transmitted over the network and is only stored on your local machine, SSH public key authentication provides a secure method of authentication. Even if the public key is intercepted, it cannot be used to gain unauthorized access without the corresponding private key.
• Convenience: Once set up, SSH key authentication allows you to access the remote server without needing to enter a password each time. This is more efficient and secure compared to password-based authentication.

Difference Between SSH and SSL/TLS

While both SSH and SSL/TLS are used to establish secure connections, they serve different purposes:

• SSH (Secure Shell): Used for securely accessing remote servers. It ensures that only authorized users can communicate with the server and provides encrypted communication.
• SSL/TLS (Secure Sockets Layer / Transport Layer Security): Used for securing data transmitted over the internet, typically between a web browser and a server. It ensures that the data is encrypted and cannot be tampered with during transmission.

How SSH Authentication Works

1. Key Pair Generation: A pair of public and private keys is generated. The public key is placed on the remote server, and the private key is kept on the client machine.
2. Establishing Secure Communication: The client initiates a connection with the server. During this process, a session key is created for encrypting the communication between the client and the server.
3. Challenge-Response Authentication: The server sends a message encrypted with the public key to the client. The client decrypts the message using its private key, combines it with the session key to create a hash, and sends it back to the server. The server then verifies the hash to authenticate the user.

Conclusion

SSH key authentication provides a secure, efficient, and convenient way to access remote servers. By understanding how it works and following the steps to set it up, you can enhance the security of your remote server access and streamline your workflow.