Keep the colleague's microbu-esp32c5 tree in this repository

obu-firmware builds against vanetza-idf from microbu-esp32c5/external, but that tree was gitignored, so a clone of this repository could not build the firmware it ships. It is now committed here as ordinary files in its own folder, microbu-esp32c5/: the colleague's commit cf4b99f plus the V2X2MAP bridge's signature verification (--trust) used on the bench. Nothing is fetched from or pushed to the colleague's repository; this repository and its remotes carry everything. The folder's own .gitignore keeps build output, downloaded components and private key material out, as it did there; the committed file set is identical to that repository's tracked files. The ESP32-C5 is still flashed from obu-firmware/, which only takes vanetza-idf from microbu-esp32c5/, so the two stay separate folders. FLASHING.md says how to take a newer version of the colleague's tree (copy it over the folder, rebuild, test, commit).
2026-09-23 17:46:40 +02:00
parent 2f60623e18
commit 0e9525162d
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+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.