[dgarske]

Description

Adds a wrap, store, reload and sign example for a HUK-wrapped ECC key to the rtl8735b example, and corrects two places where the example disagreed with the wolfSSL RealTek port.

What it adds

• huk_key_blob - the seed, IV, tag, wrapped scalar and public key an application stores
• huk_blob_create() - generates a P-256 key and wraps its scalar under the HUK with a fresh seed and IV
• huk_blob_load() - sets up a signing key from a stored blob through ecc_key->devCtx
• huk_ecdsa_reload_test() - signs from the blob, verifies with the stored public key, and checks that a damaged blob fails with AES_GCM_AUTH_E

Corrections

The README and the comment above huk_ecdsa_test() described the scalar wrap as ECB. The code and the port's wc_Rtl8735b_EccKey use AES-GCM with an IV and tag, and both now say so.

plain_gcm_badiv_test() required a non-12-byte IV to fail on the plaintext-key AES device. The port deliberately declines that request so software GCM serves it with the same literal key, so the encrypt succeeds and the test printed [FAIL]. It is now plain_gcm_long_iv_test(), which requires the encrypt to succeed and its output to match software GCM with the same key. The HUK device still hard-fails a non-12-byte IV because its key bytes are a derivation seed, and huk_gcm_badiv_test() is unchanged.

Testing

Built with the RealTek FreeRTOS SDK against current wolfSSL master and run on an RTL8735B EVB with all checks passing. A blob wrapped by one flashed image also loaded and signed correctly in a later image after a power-on reset, using a temporary test build of the example. Moving a blob to a second device was not tested, because only one board was available.

[Copilot]

🟡 Changes recommended

The damaged-blob guarantee overstates integrity protection because qx and qy are neither authenticated nor read during loading; the documentation and test description need to distinguish authenticated scalar-wrap protection from public-key integrity.

1 open issue

• Limit damaged-blob guarantee to authenticated scalar wrap · New

What changed in this PR

Adds a HUK-wrapped P-256 key reload example to the RTL8735B demo and aligns existing tests and documentation with the RealTek port’s behavior.

Changes:

• Adds a stored-key blob format and helpers to wrap, reload, and sign, with signature verification and tag-tampering checks.
• Replaces plaintext AES-GCM long-IV rejection expectations with a software-fallback comparison.
• Corrects scalar-wrapping descriptions from ECB to AES-GCM and updates sample output.

File	Description
rtl8735b/​README.md	Documents wrapped-key storage, corrects the wrapping mode, and updates expected output.
rtl8735b/​main.c	Adds blob creation and reload tests, corrects the long-IV test, and updates comments.

_{Review effort: Balanced}