in src/node_template.rs [246:252]
fn padding(idx: &TreeIndex, secret: &Secret) -> HashWiresNodeSmt<D> {
let mut hasher = D::new();
// TODO add some identifier hasher.update(PADDING_STRING.as_bytes());
hasher.update(secret.as_bytes());
hasher.update(&TreeIndex::serialize(&[*idx]));
HashWiresNodeSmt::new(hasher.finalize().to_vec())
}