# Security

[中文]

## Mbed TLS

Starting from ESP-IDF v6.0, some already deprecated mbedtls header files like `esp32/aes.h`, `esp32/sha.h`, `esp32s2/aes.h`, `esp32s2/sha.h` and `esp32s2/gcm.h` have been removed, instead, you should include `aes/esp_aes.h`, `sha/sha_core.h` and `aes/esp_aes_gcm.h` respectively.

The SHA module headers `sha/sha_dma.h` and `sha/sha_block.h` are also deprecated and removed. You should include `sha/sha_core.h` instead.

### PSA Crypto migration

In ESP-IDF v6.0, multiple ESP-IDF components have been migrated from using legacy Mbed TLS cryptography APIs (for example, `mbedtls_sha*_*()`, `mbedtls_md*_*()`, etc.) to using the PSA Crypto API.

This migration aligns ESP-IDF with Mbed TLS v4.x, where PSA Crypto is the primary cryptography interface, and it enables the use of ESP-IDF hardware acceleration through PSA drivers where available.

#### Mbed TLS v4.0 migration

ESP-IDF v6.0 updates to Mbed TLS v4.0, where PSA Crypto is the primary cryptography interface (TF-PSA-Crypto provides cryptography; Mbed TLS focuses on TLS and X.509). This can impact applications directly using Mbed TLS cryptography primitives, TLS configuration, or Mbed TLS internal/private declarations.

- Breaking change: In Mbed TLS v4.0, most legacy cryptography APIs have been removed and PSA Crypto is the primary interface. If your application directly uses legacy `mbedtls_*` cryptography primitives, you may need to migrate to PSA Crypto APIs.

- Breaking change: `psa_crypto_init()` must be called before any cryptographic operation, including indirect operations such as parsing keys/certificates or starting a TLS handshake. ESP-IDF initializes PSA during normal startup; however, code that runs earlier than the normal startup sequence must call `psa_crypto_init()` explicitly.

- New API: `esp_ecdsa_free_pk_context(mbedtls_pk_context *key_ctx)` was added (`ecdsa/ecdsa_alt.h`). If your application initializes a PK context with a hardware-backed ECDSA key using `esp_ecdsa_set_pk_context()`, use `esp_ecdsa_free_pk_context()` to free it. With PSA-backed Mbed TLS v4.x, `mbedtls_pk_free()` does not deallocate the manually created keypair structure in this case.

- Breaking change: APIs that previously required an application-provided RNG callback (`f_rng`, `p_rng`) have changed in Mbed TLS v4.0 to use the PSA RNG instead. Update application code to the new prototypes (for example X.509 write APIs, SSL cookie setup, and SSL ticket setup).

- Breaking change: TLS 1.2 / DTLS 1.2 interoperability may be affected because Mbed TLS v4.0 removes support for key exchanges based on finite-field DHE and RSA key exchange without forward secrecy (and static ECDH). If a peer requires removed suites, TLS connections may fail; update server/client cipher suite configuration accordingly.

- Breaking change: certificates/peers using elliptic curves of less than 250 bits (for example secp192r1/secp224r1) are no longer supported in certificates and in TLS.

- Note:

  - void relying on Mbed TLS private declarations (for example headers under `mbedtls/private/` or declarations enabled via `MBEDTLS_DECLARE_PRIVATE_IDENTIFIERS` / `MBEDTLS_ALLOW_PRIVATE_ACCESS`). Such private interfaces may change without notice.

  - The PSA Crypto migration (TF-PSA-Crypto) can increase flash footprint, depending on the features enabled. As reference points:

    Example | non PSA build (bytes) | PSA migration (bytes) | Diff (bytes) | Diff (%)
    --- | --- | --- | --- | ---
    protocols/esp_http_client | 609041 | 646293 | 37252 | 5.76
    protocols/https_server | 871021 | 898717 | 27696 | 3.08
    protocols/http_server/simple | 785825 | 826909 | 41084 | 4.97

#### References

- Mbed TLS 4.0 migration guide

- TF-PSA-Crypto 1.0 migration guide

- TF-PSA-Crypto PSA transition notes

#### Upstream Mbed TLS PSA notes

Some data structures and internals that applications may have accessed previously are no longer available when using PSA-backed Mbed TLS versions. If your application relied on direct access to Mbed TLS internal state (for example entropy/DRBG contexts as struct fields), migrate to supported public APIs instead.

#### PSA persistent storage (ITS) on ESP-IDF

ESP-IDF provides an implementation of PSA Internal Trusted Storage (ITS) backed by NVS, so PSA persistent storage can be used without a filesystem. If your application uses PSA persistent keys/storage, ensure that NVS is available and initialized before first use.

#### Removed deprecated APIs (Mbed TLS / crypto)

The following deprecated functions have been removed:

- `esp_aes_encrypt()` – Use `esp_internal_aes_encrypt()` instead.

- `esp_aes_decrypt()` – Use `esp_internal_aes_decrypt()` instead.

- `esp_crypto_shared_gdma_start()` – Use `esp_crypto_shared_gdma_start_axi_ahb()` instead.

Note that the new AES functions return error codes for better error handling, unlike the old void functions.

## BluFi

BluFi (Wi-Fi provisioning over BLE) is affected by the Mbed TLS v4.x / PSA Crypto migration in ESP-IDF v6.0.

- Breaking change: The BluFi protocol version has been updated (`BTC_BluFi_SUB_VER` bumped from `0x03` to `0x04`). The BluFi security negotiation implementation in ESP-IDF has been migrated to use PSA Crypto (see the updated `examples/bluetooth/blufi` example).

- Impact: Existing BluFi client applications (for example, mobile apps) built against the previous BluFi crypto/protocol implementation may no longer interoperate with devices built with ESP-IDF v6.0. This typically shows up as BluFi negotiation or connection failures during provisioning.

- Required action: Update both sides together:

  - Update the device firmware to ESP-IDF v6.0.

  - Update the BluFi client application to a version compatible with the updated BluFi protocol and security negotiation used by ESP-IDF v6.0.

## Bootloader Support

Removed Deprecated APIs

The following deprecated functions have been removed:

- `esp_secure_boot_verify_signature_block()` – Use `esp_secure_boot_verify_ecdsa_signature_block()` instead.

## NVS Security Provider

- When NVS encryption is enabled on SoCs with the HMAC peripheral that have flash encryption enabled, the HMAC-based NVS encryption scheme is now selected as default instead of the flash encryption-based scheme. If your application previously used the flash encryption-based scheme, you need to manually configure the NVS encryption scheme to flash encryption from HMAC through `menuconfig` or your project's `sdkconfig` (i.e., setting `CONFIG_NVS_SEC_KEY_PROTECT_USING_FLASH_ENC=y`).

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