Documentation
Configuration / ExternalAuthenticator.secret_key
This option should include a secret key, this key will be used in the authentication mechanism so the remote page specified with the ExternalAuthenticator.external_auth_url
needs to match this key.
$moxieManagerConfig['ExternalAuthenticator.secret_key'] = "replacemewithsomerandomkeyandkeepitsecret";
<add key="ExternalAuthenticator.secret_key" value="replacemewithsomerandomkey" />