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SSH with Git

You can use SSH for both authenticating with GitHub as well as signing commits.
This can be done with GPG, but SSH is way more straightforward.

Generate a New SSH Key

GitHub recently ended support for RSA keys.
So, generate a key that uses ed25519 encryption.

ssh-keygen -t ed25519 -C "Optional Comment"
The defaults are fine, set a passphrase if you want.

This will generate two keys: a public key and a private key.
Never share your private key with anyone.

~/.ssh/id_ed25519      # Private key
~/.ssh/id_ed25519.pub  # Public key

The public key is the one that you will be using.

SSH for GitHub Authentication

  • Generate a new ssh key if you don't have one.
  • Add your SSH public key (.pub suffix) to GitHub as an "Authentication Key" (default).
    • Settings -> GPG and SSH Keys -> Add SSH Key -> Dropdown -> Authentication Key
  • Then use ssh git@github.com to test if it worked.

SSH for Signing Commits

  • Generate a new ssh key if you don't have one.
  • Add SSH public key to github as "signing key"
    • Settings -> GPG and SSH Keys -> Add SSH Key -> Dropdown -> Signing Key

Then configure your local .gitconfig to sign commits: 

git config --global user.signingkey "/home/YOUR_USERNAME/.ssh/id_ed25519"
git config --global gpg.format ssh
git config --global tag.gpgsign true
git config --global user.signingkey ~/.ssh/id_ed25519.pub
git config --global commit.gpgSign true
mkdir -p ~/.config/git
touch ~/.config/git/allowed_signers
echo "YOUR_USERNAME $(cat ~/.ssh/id_ed25519.pub)" > ~/.config/git/allowed_signers
git config --global gpg.ssh.allowedSignersFile ~/.config/git/allowed_signers

Now you can test.
Make a change, then make a commit.
Then, run: 

git log --show-signature -1