How to Use SSH Keys Instead of Passwords for Secure Server Access

Using SSH keys instead of traditional passwords is one of the best ways to secure your server. SSH keys offer stronger encryption, eliminate the risks of brute-force attacks, and make it easier to manage automated scripts or secure user access.

In this tutorial, we’ll show you step-by-step how to generate, install, and use SSH keys on your Linux server.

✅ Why Use SSH Keys Instead of Passwords?

Here’s why switching to SSH keys is a smart move:

• ✅ Stronger Security: 2048-bit or 4096-bit SSH keys are almost impossible to brute-force.
• ✅ No Password Guessing: SSH keys eliminate password-based attacks.
• ✅ Easier Automation: Perfect for servers running scripts, cronjobs, or backups.
• ✅ Two-Factor-Like Protection: Optionally add a password to your private key for double protection.

🧰 What You’ll Need

• A Linux server with SSH access
• A local computer (Windows, macOS, or Linux)
• Terminal access or an SSH client (like PuTTY)

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🔹 Step 1: Generate SSH Key Pair

On your local machine:

ssh-keygen

You’ll be asked:

• File to save the key: (Press Enter to accept default ~/.ssh/id_rsa)
• Passphrase: (Optional, but recommended for extra security)

This generates:

• A private key: ~/.ssh/id_rsa
• A public key: ~/.ssh/id_rsa.pub

Important: Keep your private key safe and never share it!

🔹 Step 2: Copy Public Key to Server

Option 1: Using ssh-copy-id (easiest)

ssh-copy-id -i ~/.ssh/id_rsa.pub user@your-server-ip

Replace user with your username (often root) and your-server-ip with your server’s IP.

This automatically appends your public key to the server’s authorized list.

Option 2: Manual Method

If ssh-copy-id isn’t available:

1. SSH into the server with your password: bashCopyEditssh user@your-server-ip
2. Create the .ssh directory and file: bashCopyEditmkdir -p ~/.ssh nano ~/.ssh/authorized_keys
3. Paste your public key (id_rsa.pub) content into authorized_keys.
4. Set proper permissions: bashCopyEditchmod 700 ~/.ssh chmod 600 ~/.ssh/authorized_keys
5. Exit.

🔹 Step 3: Test SSH Key Login

On your local machine:

ssh user@your-server-ip

✅ If configured correctly, it should log in without asking for a password.

If you set a passphrase during key generation, it will ask for the key passphrase (not the server password).

🔒 Step 4: (Recommended) Disable Password Authentication

Once you confirm SSH key login is working:

1. SSH into your server (with key-based login).
2. Edit the SSH configuration:

nano /etc/ssh/sshd_config

Find and change:

PasswordAuthentication no
ChallengeResponseAuthentication no

Restart SSH:

systemctl restart sshd

✅ Now only SSH keys can access your server — password logins are disabled!

🛡️ Bonus Tips for SSH Security

• ✅ Use 4096-bit keys for even stronger encryption: ssh-keygen -b 4096
• ✅ Backup your private keys securely
• ✅ Rotate keys periodically
• ✅ Use Fail2Ban or CSF to block failed SSH attempts

📌 Common SSH Key Commands Cheat Sheet

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