Secure Remote Server Access use SSH Key Authentication

To replace password-based SSH authentication with SSH key authentication, follow these steps:

Understanding SSH Key Authentication

SSH key authentication is a secure method for accessing remote servers without using passwords. Here’s what you need to know:

• Key Pair: SSH uses a public-private key pair for authentication.
• Security: It’s more secure than password-based authentication.
• Convenience: Once set up, it allows for password-less logins.

Setting Up SSH Keys in Your Local Machine

Follow these steps to set up SSH key authentication:

1. Generate the key pair on your local machine:

   ssh-keygen -t ed25519 -C "your_email@example.com"
   

2. Copy the public key to the server:

   ssh-copy-id username@remote_host
   

3. Ensure proper permissions:

   chmod 600 ~/.ssh/id_ed25519
   chmod 644 ~/.ssh/id_ed25519.pub
   

Ed25519 vs RSA: Choosing Your Key Type

When generating SSH keys, you’ll encounter different algorithms. Here’s a comparison of Ed25519 and RSA:

Ed25519 is recommended for new deployments due to its superior security and performance.

Configuring SSH on the Server

1. Create the .ssh directory if it doesn’t exist:

   mkdir -p ~/.ssh && chmod 700 ~/.ssh
   

2. Create or edit the authorized_keys file:

   nano ~/.ssh/authorized_keys
   

   Paste the public key you copied from your local machine into this file.

3. Set the correct permissions:

   chmod 600 ~/.ssh/authorized_keys
   

4. Modify the SSH configuration to enable key-based authentication:

   sudo nano /etc/ssh/sshd_config
   

   Ensure these lines are set:

   PubkeyAuthentication yes
   PasswordAuthentication no
   

5. Restart the SSH service:

   sudo systemctl restart sshd
   

Conect to Server using SSH Key Authentication

Test the connection:

ssh -i /path/to/your/private_key username@remote_host

Troubleshooting Common SSH Issues

If you encounter issues, try these solutions:

1. Permission denied (publickey): Check key permissions and authorized_keys file.
2. Too open permissions: Use chmod 600 for private keys and chmod 644 for public keys.
3. Invalid format: Ensure you’re using the private key, not the public key (.pub file).