Function shs_core::server_to_client_key

pub fn server_to_client_key(
    server_pk: &ClientPublicKey, 
    net_key: &NetworkKey, 
    shared_a: &SharedA, 
    shared_b: &SharedB, 
    shared_c: &SharedC
) -> Key

Final shared key used to seal and open secret boxes (server to client)