How SSH Works: Generate and Use SSH Keys on Windows with PuTTY

What is SSH?

SSH (Secure Shell) is a protocol that provides a secure channel over an unsecured network. It encrypts all communication, ensuring sensitive data like usernames, passwords, and files remain confidential.

SSH Keys: .ppk, .pem, and RSA Explained

SSH relies on cryptographic keys, eliminating reliance on passwords. Here’s what these key formats mean:

.pem (Privacy Enhanced Mail): Used primarily on Linux or cloud platforms like AWS. It’s a universal OpenSSH-compatible format.
.ppk (PuTTY Private Key): Specifically for Windows users utilizing PuTTY.
RSA keys: Keys generated using RSA encryption, available in .pem or .ppk formats.

Generating SSH Keys in Windows using PuTTYgen

Follow these steps to generate SSH keys using PuTTYgen:

Download and open PuTTYgen.
Select RSA key type (default) and click Generate.
Move your mouse randomly in the box to generate randomness.
Optional: Add a key comment and set a passphrase for additional security.
Click “Save private key” to save your file as .ppk.
To use a .pem file, choose “Conversions” → “Export OpenSSH key”, saving the file with a .pem extension.

Connecting to a Server using PuTTY

To SSH into your server:

Launch PuTTY.
Enter your server’s IP or hostname.
Under “Connection → SSH → Auth”, select your saved .ppk file.
Return to “Session”, click “Open”, and enter your server’s username when prompted.

Troubleshooting Common Issues

Permission errors: Ensure key permissions are properly set (e.g., chmod 400 key.pem on Linux).
Authentication failure: Verify correct username and key file.
Connection timeout: Check network and firewall settings.

Best Practices for SSH Security

Always secure and backup your private keys.
Regularly rotate your SSH keys.
Avoid using passwords—use key-based authentication whenever possible.

Conclusion: SSH is critical for secure server access and administration. Understanding key formats, generating them securely, and correctly using PuTTY enhances security and efficiency.

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