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ssh-keygen

Introduction​

This cheat sheet provides a quick reference for some common ssh-keygen commands and concepts. ssh-keygen is a command-line tool used to generate and manage SSH keys for secure authentication.

ssh-keygen Concepts​

Basic ssh-keygen Usage​

ssh-keygen is used for creating and managing SSH key pairs.

  • Generate a new SSH key pair (RSA):

    ssh-keygen -t rsa

  • Generate an SSH key with a specific length:

    ssh-keygen -t rsa -b 4096

  • Generate an SSH key pair with a custom file name:

    ssh-keygen -t rsa -f my-key

Passphrases​

Adding a passphrase to an SSH key provides an additional layer of security.

  • Generate an SSH key with a passphrase:
    ssh-keygen -t rsa -b 4096 -f my-key -C "Key for secure access" -N "my-passphrase"

Viewing and Managing Keys​

ssh-keygen also allows you to view and manage existing keys.

  • View the public key from a private key file:

    ssh-keygen -y -f private-key-file

  • Add an SSH key to the SSH agent:

    ssh-add /path/to/ssh-key

  • List keys stored in the SSH agent:

    ssh-add -l

  • Remove a key from the SSH agent:

    ssh-add -d /path/to/ssh-key

SSH Key Fingerprints​

SSH key fingerprints are used to verify key authenticity.

  • Display the fingerprint of an SSH public key:
    ssh-keygen -lf /path/to/public-key

Converting Key Formats​

ssh-keygen can convert keys between different formats.

  • Convert an OpenSSH key to a different format (e.g., PKCS#8):
    ssh-keygen -p -m PKCS8 -f /path/to/openssh-key

ssh-keygen Command-Line​

  • Generate a new SSH key pair (RSA):

    ssh-keygen -t rsa

  • Generate an SSH key with a specific length:

    ssh-keygen -t rsa -b 4096

  • Generate an SSH key pair with a custom file name:

    ssh-keygen -t rsa -f my-key

  • Generate an SSH key with a passphrase:

    ssh-keygen -t rsa -b 4096 -f my-key -C "Key for secure access" -N "my-passphrase"

  • View the public key from a private key file:

    ssh-keygen -y -f private-key-file

  • Add an SSH key to the SSH agent:

    ssh-add /path/to/ssh-key

  • List keys stored in the SSH agent:

    ssh-add -l

  • Remove a key from the SSH agent:

    ssh-add -d /path/to/ssh-key

  • Display the fingerprint of an SSH public key:

    ssh-keygen -lf /path/to/public-key

  • Convert an OpenSSH key to a different format (e.g., PKCS#8):

    ssh-keygen -p -m PKCS8 -f /path/to/openssh-key

Conclusion​

This cheat sheet covers some common ssh-keygen commands and concepts. ssh-keygen is a valuable tool for generating and managing SSH keys, providing secure authentication for remote access; refer to the OpenSSH documentation for more in-depth information and advanced usage.