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GitHub changed which keys are supported in SSH and removed the unencrypted Git protocol.
You can read more about the motivation behind these changes in our blog post from last September.
As a reminder, these changes were:

  • Removed all support for DSA keys
  • Required SHA-2 signatures on all RSA keys uploaded after November 2, 2021 (RSA keys uploaded prior to the cutoff may still use SHA-1 signatures)
  • Removed legacy SSH algorithms HMAC-SHA-1 and CBC ciphers
  • Permanently disabled the unencrypted Git protocol
See more

The GitHub metadata endpoint now contains our SSH host keys.
(We'll continue offering host key fingerprints as well.)

{
  // new entry
  "ssh_keys": [
    "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIOMqqnkVzrm0SdG6UOoqKLsabgH5C9okWi0dh2l9GKJl",
    "ecdsa-sha2-nistp256 AAAAE2VjZHNhLXNoYTItbmlzdHAyNTYAAAAIbmlzdHAyNTYAAABBBEmKSENjQEezOmxkZMy7opKgwFB9nkt5YRrYMjNuG5N87uRgg6CLrbo5wAdT/y6v0mKV0U2w0WZ2YB/++Tpockg=",
    "ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEAq2A7hRGmdnm9tUDbO9IDSwBK6TbQa+PXYPCPy6rbTrTtw7PHkccKrpp0yVhp5HdEIcKr6pLlVDBfOLX9QUsyCOV0wzfjIJNlGEYsdlLJizHhbn2mUjvSAHQqZETYP81eFzLQNnPHt4EVVUh7VfDESU84KezmD5QlWpXLmvU31/yMf+Se8xhHTvKSCZIFImWwoG6mbUoWf9nzpIoaSjB+weqqUUmpaaasXVal72J+UX2B+2RPW3RcT0eOzQgqlJL3RKrTJvdsjE3JEAvGq3lGHSZXy28G3skua2SmVi/w4yCE6gbODqnTWlg7+wC604ydGXA8VJiS5ap43JXiUFFAaQ=="
  ],
  // existing entry
  "ssh_key_fingerprints": [
    "SHA256_RSA": "nThbg6kXUpJWGl7E1IGOCspRomTxdCARLviKw6E5SY8",
    "SHA256_ECDSA": "p2QAMXNIC1TJYWeIOttrVc98/R1BUFWu3/LiyKgUfQM",
    "SHA256_ED25519": "+DiY3wvvV6TuJJhbpZisF/zLDA0zPMSvHdkr4UvCOqU"
  ],
  // ... rest of payload
}

These keys are in the OpenSSH known_hosts format for easy inclusion into existing known_hosts files.
This will make it easier to preconfigure systems which expect to connect via SSH.
For example, you can prime your CI runners with these keys before starting to fetch from GitHub.

The keys returned from the API include both SSH host keys that we're actively using, plus any that we're advertising via host key rotation for future use.
Currently, we're not offering any keys via rotation that aren't actively in use, but if we announce new host keys in the future, you can find them here as well during the rotation period.

See the meta API endpoint to learn more.

See more

You can now authenticate to SSH using a FIDO2 security key by adding a sk-ecdsa-sha2-nistp256@openssh.com or sk-ssh-ed25519@openssh.com SSH key to your account. SSH security keys store secret key material on a separate hardware device that requires verification, such as a tap, to operate.

This combination of storing the key on separate hardware and requiring physical interaction for your SSH key offers additional security. Since the key is stored on hardware and is non-extractable, it can't be read or stolen by software running on the computer. Additionally, the tap prevents unauthorized use of the key since the security key will not operate until you physically interact with it.

Learn more about this feature from the accompanying blog post.

Learn more about adding an SSH key to your account.

See more