Reference notes
===============

Pinned upstream commit:
e3bb3b82480d6df4237e2a8c35ea0dd7eade25b4

The upstream commit's root generator:
1. constructs a ToBeSignedCertificate;
2. serializes it using rasn::oer::encode();
3. calls PrivateKey::sign(hash_alg, &tbs_bytes, None);
4. inserts the returned IEEE 1609.2 Signature into an ExplicitCertificate.

The pinned c-its PrivateKey::sign() implementation for SHA-256 computes:

    SHA256(
        SHA256(tbs_bytes)
        ||
        SHA256(signer_info)
    )

For a self-signed root, signer_info is the empty byte string because the root
generator passes None.

This bundle uses that exact upstream code for the cryptographic operation.
`rebuild_registered_rca.py` keeps the registered TBS/public key unchanged and uses
the registered encrypted key. `create_new_root.py` creates a new encrypted key and
replaces the template public key for a separate, unregistered candidate root. In
both cases the scalar reaches Rust only through standard input.