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" />