Hi Roman,

Yes that would be doable. PSA supports vendor algorithms not defined in the spec, just make sure that your custom alg has the vendor flag set to avoid conflicts:

/** Vendor-defined algorithm flag.

*

* Algorithms defined by this standard will never have the #PSA_ALG_VENDOR_FLAG

* bit set. Vendors who define additional algorithms must use an encoding with

* the #PSA_ALG_VENDOR_FLAG bit set and should respect the bitwise structure

* used by standard encodings whenever practical.

*/

#define PSA_ALG_VENDOR_FLAG                     ((psa_algorithm_t) 0x80000000)

Current default crypto_platform.h is empty, I think it would make sense that a platform could point to its own crypto_platform.h replacing the default one. Note that we already have a mechanism in place after a very recent change to the headers (last month) that allows for the same thing you’re proposing:

#if defined(MBEDTLS_PSA_CRYPTO_PLATFORM_FILE)

#include MBEDTLS_PSA_CRYPTO_PLATFORM_FILE

#else

#include "crypto_platform.h"

#endif

Alternative could be to extend the current empty crypto_platform.h in TF-M with the inclusion of a platform specific include header that gets included only for your platform.

Thanks, Antonio

From: Roman.Mazurak--- via TF-M <tf-m@lists.trustedfirmware.org>
Sent: Wednesday, April 19, 2023 11:08
To: tf-m@lists.trustedfirmware.org
Subject: [TF-M] PSA Crypto platform specific extensions

Hello everyone,

I need to extend PSA Crypto API by adding a platform specific encryption algorithm/key attribute.  For example a vendor specific algorithm named ABC must be added. So, I need that following macro must be included when psa/crypto.h is included.

#define PSA_ALG_ABC                                 ((psa_algorithm_t) 0x08000123)

TF-M provides PSA Crypto interface through includes located in interface/include/psa/crypto*.h. It means that we need to extend TF-M by allowing platform to provide some platform specific crypto header that will be installed in interface folder and included by psa/crypto.h.

1. Is there any activity related to this problem?
2. I’m considering to create a new crypto_config.h that must be generated during build process and which can optionally provide a macro TFM_PLATFORM_CRYPTO_EXTRA. These macro will be used in psa/crypto.h to conditionally include crypto_platform.h – header provided by platform.

Thanks,

Roman.