Skip to main content

SSH Key Files in Linux Authentication

SSH (Secure Shell) is a protocol used to securely log into remote systems. Instead of using a password, you can authenticate using SSH key pairs. This method is more secure and commonly used for managing remote servers, especially in cloud environments like AWS.

🔐 What are SSH Keys?​

SSH key-based authentication uses a pair of cryptographic keys:

  • Private Key – kept secret by the user.
  • Public Key – placed on the remote system you want to access.

📁 Common SSH Key File Formats​

.pem (Privacy Enhanced Mail)​

  • Default format for AWS EC2 key pairs.
  • PEM files are used by OpenSSH (Linux/macOS) for SSH authentication.
  • Typically used directly with the ssh command.

.ppk (PuTTY Private Key)​

  • A format used by PuTTY, a popular SSH client on Windows.
  • You can convert .pem to .ppk using PuTTYgen.

🔧 Using SSH Keys in Linux​

1. Connect Using a .pem File​

If you have a .pem file (e.g., from AWS EC2):

chmod 400 my-key.pem
ssh -i my-key.pem username@remote-host