To sign commits locally, you need to inform Git that there's a GPG or X.509 key you'd like to use.

In this article:

Telling Git about your GPG key

If you're using a GPG key that matches your committer identity and your verified email address associated with your GitHub account, then you can begin signing commits and signing tags.

If you don't have a GPG key that matches your committer identity, you need to associate an email with an existing key. For more information, see "Associating an email with your GPG key".

If you have multiple GPG keys, you need to tell Git which one to use.

  1. Open TerminalTerminalGit Bash.

  2. Use the gpg --list-secret-keys --keyid-format LONG command to list GPG keys for which you have both a public and private key. A private key is required for signing commits or tags.

    gpg --list-secret-keys --keyid-format LONG
    

    Note: Some GPG installations on Linux may require you to use gpg2 --list-keys --keyid-format LONG to view a list of your existing keys instead. In this case you will also need to configure Git to use gpg2 by running git config --global gpg.program gpg2.

  3. From the list of GPG keys, copy the GPG key ID you'd like to use. In this example, the GPG key ID is 3AA5C34371567BD2:

    gpg --list-secret-keys --keyid-format LONG
    /Users/hubot/.gnupg/secring.gpg
    ------------------------------------
    sec   4096R/3AA5C34371567BD2 2016-03-10 [expires: 2017-03-10]
    uid                          Hubot 
    ssb   4096R/42B317FD4BA89E7A 2016-03-10
    
  4. To set your GPG signing key in Git, paste the text below, substituting in the GPG key ID you'd like to use. In this example, the GPG key ID is 3AA5C34371567BD2:

    git config --global user.signingkey 3AA5C34371567BD2
    
  5. If you aren't using the GPG suite, paste the text below to add the GPG key to your bash profile:

    test -r ~/.bash_profile && echo 'export GPG_TTY=$(tty)' >> ~/.bash_profile
    echo 'export GPG_TTY=$(tty)' >> ~/.profile
    

    Note: If you don't have .bash_profile, this command adds your GPG key to .profile.

  1. Open TerminalTerminalGit Bash.

  2. Use the gpg --list-secret-keys --keyid-format LONG command to list GPG keys for which you have both a public and private key. A private key is required for signing commits or tags.

    gpg --list-secret-keys --keyid-format LONG
    

    Note: Some GPG installations on Linux may require you to use gpg2 --list-keys --keyid-format LONG to view a list of your existing keys instead. In this case you will also need to configure Git to use gpg2 by running git config --global gpg.program gpg2.

  3. From the list of GPG keys, copy the GPG key ID you'd like to use. In this example, the GPG key ID is 3AA5C34371567BD2:

    gpg --list-secret-keys --keyid-format LONG
    /Users/hubot/.gnupg/secring.gpg
    ------------------------------------
    sec   4096R/3AA5C34371567BD2 2016-03-10 [expires: 2017-03-10]
    uid                          Hubot 
    ssb   4096R/42B317FD4BA89E7A 2016-03-10
    
  4. To set your GPG signing key in Git, paste the text below, substituting in the GPG key ID you'd like to use. In this example, the GPG key ID is 3AA5C34371567BD2:

    git config --global user.signingkey 3AA5C34371567BD2
    
  1. Open TerminalTerminalGit Bash.

  2. Use the gpg --list-secret-keys --keyid-format LONG command to list GPG keys for which you have both a public and private key. A private key is required for signing commits or tags.

    gpg --list-secret-keys --keyid-format LONG
    

    Note: Some GPG installations on Linux may require you to use gpg2 --list-keys --keyid-format LONG to view a list of your existing keys instead. In this case you will also need to configure Git to use gpg2 by running git config --global gpg.program gpg2.

  3. From the list of GPG keys, copy the GPG key ID you'd like to use. In this example, the GPG key ID is 3AA5C34371567BD2:

    gpg --list-secret-keys --keyid-format LONG
    /Users/hubot/.gnupg/secring.gpg
    ------------------------------------
    sec   4096R/3AA5C34371567BD2 2016-03-10 [expires: 2017-03-10]
    uid                          Hubot 
    ssb   4096R/42B317FD4BA89E7A 2016-03-10
    
  4. To set your GPG signing key in Git, paste the text below, substituting in the GPG key ID you'd like to use. In this example, the GPG key ID is 3AA5C34371567BD2:

    git config --global user.signingkey 3AA5C34371567BD2
    
  5. To add your GPG key to your bash profile, paste the text below:

    test -r ~/.bash_profile && echo 'export GPG_TTY=$(tty)' >> ~/.bash_profile
    echo 'export GPG_TTY=$(tty)' >> ~/.profile
    

    Note: If you don't have .bash_profile, this command adds your GPG key to .profile.

Telling Git about your X.509 key

You can use smimesign to sign commits and tags using S/MIME instead of GPG.

Note: S/MIME signature verification is available in Git 2.19 or later. To update your version of Git, see the Git website.

  1. Install smimesign.
  2. Open TerminalTerminalGit Bash.

  3. Configure Git to use S/MIME to sign commits and tags. In Git 2.19 or later, use the git config gpg.x509.program and git config gpg.format commands:

    • To use S/MIME to sign for all repositories:

      git config --global gpg.x509.program smimesign
      git config --global gpg.format x509
      
    • To use S/MIME to sign for a single repository:

      cd /path/to/my/repository
      git config --local gpg.x509.program smimesign
      git config --local gpg.format x509
      

    In Git 2.18 or earlier, use the git config gpg.program command:

    • To use S/MIME to sign for all repositories:

      git config --global gpg.program smimesign
      
    • To use S/MIME to sign for a single repository:

      cd /path/to/my/repository
      git config --local gpg.program smimesign
      

    If you're using an X.509 key that matches your committer identity, you can begin signing commits and tags.

  4. If you're not using an X.509 key that matches your commiter identity, list X.509 keys for which you have both a certificate and private key using the smimesign --list-keys command.

    smimesign --list-keys
    
  5. From the list of X.509 keys, copy the certificate ID of the X.509 key you'd like to use. In this example, the certificate ID is 0ff455a2708394633e4bb2f88002e3cd80cbd76f:

    smimesign --list-keys
               ID: 0ff455a2708394633e4bb2f88002e3cd80cbd76f
              S/N: a2dfa7e8c9c4d1616f1009c988bb70f
        Algorithm: SHA256-RSA
         Validity: 2017-11-22 00:00:00 +0000 UTC - 2020-11-22 12:00:00 +0000 UTC
           Issuer: CN=DigiCert SHA2 Assured ID CA,OU=www.digicert.com,O=DigiCert Inc,C=US
          Subject: CN=Octocat,O=GitHub\, Inc.,L=San Francisco,ST=California,C=US
           Emails: octocat@github.com
    
  6. To set your X.509 signing key in Git, paste the text below, substituting in the serial number you'd like to use. In this example, the serial number is a2dfa7e8c9c4d1616f1009c988bb70f:

    • To use your X.509 key to sign for all repositories:

      git config --global user.signingkey a2dfa7e8c9c4d1616f1009c988bb70f
      
    • To use your X.509 key to sign for a single repository:

      cd /path/to/my/repository
      git config --local user.signingkey a2dfa7e8c9c4d1616f1009c988bb70f
      

Further reading