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Document driver-only hashes

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Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
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Manuel Pégourié-Gonnard 2023-09-22 10:15:22 +02:00
parent cc21ad441a
commit 1f61b7b8ea
2 changed files with 27 additions and 2 deletions
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3
ChangeLog.d/driver-only-hashes.txt
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@ -7,4 +7,5 @@ Features
provided - these limitations are lifted in this version. A new set of
feature macros, MBEDTLS_MD_CAN_xxx, has been introduced that can be used
to check for availability of hash algorithms, regardless of whether
they're provided by a built-in implementation, a driver or both.
they're provided by a built-in implementation, a driver or both. See
docs/driver-only-builds.md.

26
docs/driver-only-builds.md
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@ -71,7 +71,31 @@ you're interested in driver-only support for RSA, please let us know.
Hashes
------
TODO
If is possible to have all hash operations provided only by a driver.
More precisely:
- you can enable `PSA_WANT_ALG_SHA_256` without `MBEDTLS_SHA256_C`, provided
you have `MBEDTLS_PSA_ACCEL_ALG_SHA_256` enabled;
- and similarly for all supported hash algorithms: `MD5`, `RIPEMD160`,
`SHA_1`, `SHA_224`, `SHA_256`, `SHA_384`, `SHA_512`, `SHA3_224`, `SHA3_256`,
`SHA3_384`, `SHA3_512`.
In such a build, all crypto operations (via the PSA Crypto API, or non-PSA
APIs), as well as X.509 and TLS, will work as usual, except that direct calls
to low-level hash APIs (`mbedtls_sha256()` etc.) are not possible for the
modules that are disabled.
You'll need to call `psa_crypto_init()` before any crypto operation that uses
a hash algorithm that's provided only by a driver, as mentioned in [General
considerations](#general-considerations) above.
If you want to check at compile-time whether a certain hash algorithm is
available in the present build of Mbed TLS, regardless of whether it's
provided by a driver or built-in, you should use the following macros:
- for code that uses only the PSA Crypto API: `PSA_WANT_ALG_xxx` from
`psa/crypto.h`;
- for code that may also use non-PSA crypto APIs: `MBEDTLS_MD_CAN_xxx` from
`mbedtls/md.h`.
Elliptic-curve cryptography (ECC)
---------------------------------