1. Go to Settings > Certificates and Key Pairs.
  2. Locate the key you want to set as default.
  3. Click the details icon to expand the appropriate key.
  4. Do one of the following:
    • For a signing key, click Make Default Signing Key. In the confirmation message, click Continue.
    • For an encryption key, click Make Default Encryption Key. In the confirmation message, click Continue.
    Note:

    You can’t set expired keys as default.

The default key is indicated with a Default label.