How to Generate a Git SSH Key on Your Mac and Add it to GitHub

SSH (Secure Shell) keys play a crucial role in ensuring that your data remains protected during transit. In this tutorial, we will walk you through the steps to generate a new SSH key and quickly add it to your Mac.

Open Terminal

You can find Terminal in your Applications folder under Utilities or by searching for it using Spotlight (press Command + Space and type "Terminal").

Check for existing SSH keys

Run the following command to see if you already have SSH keys:

ls -al ~/.ssh

If you see files named id_rsa and id_rsa.pub, you already have SSH keys. If not, continue below.

Generate a new SSH key

Use the command below to generate a new SSH key. Replace your email with the one you use for Git:

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

When prompted, you can press Enter to accept the default file location (usually ~/.ssh/id_ed25519). You can also set a passphrase for added security.

You can now verify that the keys have been created, by running the following command:

ls -l ~/.ssh

You will normally see that the two keys have been created.

Start the SSH agent

Run the following command to start the SSH agent:

eval "$(ssh-agent -s)"

It will print out something like this:

Agent pid 18608

Add a config file for your keys

If you're using macOS Sierra 10.12.2 or later, you will need to modify your ~/.ssh/config file to automatically load keys into the ssh-agent and store passphrases in your keychain.

If the file doesn't exist, create the file.

touch ~/.ssh/config

Open your ~/.ssh/config file, then modify the file to contain the following lines.

Host github.com
  AddKeysToAgent yes
  UseKeychain yes
  IdentityFile ~/.ssh/id_ed25519

Add your SSH key to the SSH agent

Use the following command to add your SSH key:

ssh-add --apple-use-keychain ~/.ssh/id_ed25519

Copy the SSH key to your clipboard

You can copy your SSH public key to your clipboard with this command:

pbcopy < ~/.ssh/id_id_ed25519.pub

Add the SSH key to your Git account

1. Go to your Git hosting service (like GitHub, GitLab, or Bitbucket).
2. Navigate to SSH key settings (typically found in account settings).
3. Paste your SSH key into the provided field and save it.

Test your SSH connection

Run the following command to test your SSH connection:

ssh -T git@github.com

You will see a prompt that says, "The authenticity of host 'github.com (ip_address)' can't be established." You will see the key fingerprint in the format SHA256:....

Add the fingerprint to the known_hosts file

When you see the prompt about the authenticity of the host, verify the fingerprint against the official GitHub SSH key fingerprints found here. If it matches, type yes and press Enter to add the host to your known_hosts file.

Conclusion

You have successfully installed and configured your Git SSH key on your Mac and added the fingerprint to your known_hosts file! You can now use Git with SSH authentication.