esp32_crypto

The ESP32’s SHA and AES hardware accelerators.

These are the hardware behind the shapes in crypto: [sha] produces SHA-1 and SHA-256 digests, [aes] does single-block AES-128/256 ECB. The software lib stays as the thing they are checked against — the on-target self-test runs both paths over the same input and asserts byte-for-byte equality, so a hardware bug cannot hide behind a passing protocol test (see #33 and the crypto crate docs).

Both blocks live in the DPORT window

DR_REG_AES_BASE (0x3FF0_1000) and DR_REG_SHA_BASE (0x3FF0_3000) are inside the DPORT address range, which has two consequences a driver here must respect and neither is optional:

• Reads of these registers — the digest, the AES output, the busy flag — take the erratum-safe dport::read, not a plain volatile load. A raw read can return an unrelated APB value when the other core touches the bus (soc-esp32 dport docs, bug #56). Writes are plain, exactly as esp-idf’s DPORT_REG_WRITE/esp_dport_access_read_buffer split says.
• The block’s clock is gated by DPORT_PERI_CLK_EN, a different register from the PERIP_CLK_EN the rest of the chip uses. That is why this calls dport::enable_crypto, not dport::enable.

Byte order is the classic gotcha

The two blocks disagree, and getting it wrong yields a digest that is a byte-swapped version of the right answer — plausible enough to pass a glance and fail every vector. Each module states its own convention where it writes and reads the registers; both are pinned by the cross-check against the software lib, which is the only test that can catch a swap.

References, read rather than recalled: esp-idf hal/esp32/include/hal/sha_ll.h + aes_ll.h, hal/sha_hal.c + aes_hal.c, and soc/esp32/include/soc/hwcrypto_reg.h.

Modules

• aes — The ESP32 AES accelerator: single-block AES-128/256 ECB.
• sha — The ESP32 SHA accelerator: one-shot SHA-1 and SHA-256 over a byte slice.

Enums

CryptoError

enum CryptoError {
    Timeout,
}

A crypto transform could not complete.

Implements: Clone, Copy, Debug, Eq, From, PartialEq, StructuralPartialEq