Add SRAM PUF (Physically Unclonable Function) support to wolfCrypt. Derives device-unique cryptographic keys from the power-on state of SRAM memory using a BCH(127,64,t=10) fuzzy extractor with HKDF key derivation.
- **wolfCrypt PUF API** (`wolfcrypt/src/puf.c`, `wolfssl/wolfcrypt/puf.h`)
- `wc_PufInit`, `wc_PufReadSram`, `wc_PufEnroll`, `wc_PufReconstruct`
- `wc_PufDeriveKey` (HKDF-SHA256), `wc_PufGetIdentity` (SHA-256 device fingerprint)
- `wc_PufZeroize` (secure context cleanup)
- `wc_PufSetTestData` (synthetic SRAM for testing without hardware)
- **BCH(127,64,t=10) error-correcting codec** - corrects up to 10 bit flips per 127-bit codeword across 16 codewords
- **`WC_PUF_SHA3` build option** - select SHA3-256 instead of SHA-256 for identity hash and HKDF (default: SHA-256)
- **Precomputed GF(2^7) tables** - `const` arrays in `.rodata` (no runtime init, thread-safe, flash-resident on embedded)
- `./configure --enable-puf` (auto-enables HKDF dependency)
- CMake: `WOLFSSL_PUF=yes`
- `WOLFSSL_USER_SETTINGS`: define `WOLFSSL_PUF` and `WOLFSSL_PUF_SRAM`
- See wolfssl-examples/puf for example implementation on STM32 NUCLEO-H563ZI (Cortex-M33, STM32H563ZI)
- Supports test mode (synthetic SRAM)
- Builds to ~13KB `.elf`
- Tested on NUCLEO-H563ZI: enrollment, noisy reconstruction, key derivation all pass
- `.github/workflows/puf.yml`: host build + test workflow for PUF feature
- Doxygen API docs for all 8 public functions
- PUF group added to `doxygen_groups.h`
Add CryptoCB-based AES key import support to enable Secure Element
offload without exposing raw AES key material to wolfCrypt.
When WOLF_CRYPTO_CB_AES_SETKEY is defined, wolfCrypt invokes a CryptoCB
callback during AES key setup. Behavior is determined by the callback
return value:
- If callback returns 0: Key is imported to the device (aes->devCtx).
Key is NOT copied to wolfCrypt RAM; GCM H/M tables are NOT generated.
Full hardware offload is assumed.
- If callback returns CRYPTOCB_UNAVAILABLE: Device does not support
SetKey. Normal software path is used; key is copied to devKey for
optional encrypt/decrypt acceleration.
- Any other error: Propagated to the caller.
Key points:
- Add wc_CryptoCb_AesSetKey() callback for AES key import
- Update AES SetKey paths to call CryptoCB and branch on return value
- Skip GCM H/M table generation when callback succeeded (devCtx set)
- Preserve existing behavior when devId is INVALID_DEVID or
WOLF_CRYPTO_CB_AES_SETKEY is not defined
Testing:
- Add unit test for CryptoCB AES SetKey (verifies key isolation when
callback succeeds)
- Add end-to-end AES-GCM offload test (SetKey, Encrypt, Decrypt, Free
via CryptoCB)
- Tests use a mock SE with software AES to validate routing
Enable with: CPPFLAGS="-DWOLF_CRYPTO_CB_AES_SETKEY -DWOLF_CRYPTO_CB_FREE"
Signed-off-by: Sameeh Jubran <sameeh@wolfssl.com>
David Garske
Michael Rogov Papernov
JacobBarthelmeh
Sameeh Jubran
Josh Holtrop
Eric Blankenhorn
gojimmypi
Joshua Okeleke
Daniel Pouzzner
Chris Conlon
Juliusz Sosinowicz
John Safranek