Hardware and Platforms

Hardware Acceleration

wolfSSL ships more than 30 hardware and platform ports in wolfcrypt/src/port/ (NXP, ST, Renesas, Microchip, Cypress PSoC 6, Silicon Labs, Espressif, Xilinx, Intel QuickAssist and more), plus hand-optimized assembly for Intel AES-NI/AVX, ARMv8 and RISC-V. Check that directory for your part before writing a driver.

Crypto Callbacks

For hardware without an in-tree port, the crypto callback interface (--enable-cryptocb) is the one hook you implement. Compared with the alternatives in Mbed TLS:

• Crypto _ALT macros (3.6) replace a software implementation at compile time, for every caller. They are gone in 4.x.
• PSA drivers (4.x) follow a specification still marked beta. Only part of the dispatch layer is code-generated, and the rest is wired up by hand.
• wolfSSL crypto callbacks are registered at runtime under a device ID that an object or a whole TLS context opts into. A callback returns CRYPTOCB_UNAVAILABLE to fall back to software, and the interface covers hashes, ciphers, MACs, RNG and the classic and post-quantum public-key algorithms, so a secure element or HSM can take over ML-KEM or ML-DSA as well. ML-KEM decapsulation with a key held only by the device needs a wolfSSL release after 5.9.4.

Offloading ECDSA signing for every TLS connection on a context looks like this:

#include <wolfssl/options.h>
#include <wolfssl/wolfcrypt/cryptocb.h>
#include <wolfssl/ssl.h>

#define MY_HW_DEVID 0x48570001

int my_hw_ecdsa_sign(const byte* hash, word32 hashSz, byte* sig,
                     word32* sigSz, ecc_key* key);

static int myHwCallback(int devId, wc_CryptoInfo* info, void* ctx)
{
    (void)devId;
    (void)ctx;
    if (info->algo_type == WC_ALGO_TYPE_PK &&
        info->pk.type == WC_PK_TYPE_ECDSA_SIGN) {
        return my_hw_ecdsa_sign(info->pk.eccsign.in, info->pk.eccsign.inlen,
                                info->pk.eccsign.out, info->pk.eccsign.outlen,
                                info->pk.eccsign.key);
    }
    return CRYPTOCB_UNAVAILABLE; /* everything else stays in software */
}

int use_hw(WOLFSSL_CTX* ctx)
{
    if (wc_CryptoCb_RegisterDevice(MY_HW_DEVID, myHwCallback, NULL) != 0)
        return -1;
    return wolfSSL_CTX_SetDevId(ctx, MY_HW_DEVID) == WOLFSSL_SUCCESS ? 0 : -1;
}

sig receives a DER signature; convert raw r and s with wc_ecc_rs_raw_to_sig(). To keep the private key in the secure element, load it with wolfSSL_CTX_use_PrivateKey_Id() and the same device ID. The same mechanism powers wolfHSM, wolfTPM and PKCS#11, and PK callbacks (--enable-pkcallbacks) offer a TLS-level alternative.

Call use_hw() before wolfSSL_new(): each WOLFSSL takes the context's device ID when it is created. For a session that already exists, set it with wolfSSL_SetDevId().

Zephyr

Zephyr's TLS sockets (SOL_TLS) are built on Mbed TLS. wolfSSL ships a Zephyr module, and the wolfSSL OSP repository has a patch for each supported Zephyr release that switches the TLS sockets to wolfSSL; re-apply it when you move to a new release. Subsystems that use the PSA Crypto API, such as Bluetooth, run on wolfCrypt unchanged with wolfPSA as Zephyr's PSA crypto provider.

ESP-IDF

wolfSSL is available as a managed component in the Espressif Component Registry. Build instructions and examples are in IDE/Espressif in the wolfSSL repository.

Other Platforms

wolfSSL has projects for more than 60 IDEs and platforms in its IDE/ directory, plus Arduino and PlatformIO packages and Linux and BSD kernel modules. Builds without a configure step use user_settings.h, with templates in examples/configs/.