Function verify_response 

pub fn verify_response(
    s: &SignedCtl,
    request: &CtlRequest,
    expected: Option<&[u8; 32]>,
) -> Result<(CtlResponse, [u8; 32]), Refusal>

Verify a response to request from the node whose key is expected (None accepts any key, then binds responder to it: describe to an unknown node). Returns the response and the responder’s key.