19 Jul
2021
19 Jul
'21
2:08 p.m.
Hello,
Mbed TLS has never supported a build with SHA-256 but not SHA-224. In Mbed TLS 2.x, enabling MBEDTLS_SHA256_C enables both SHA-256 and SHA-224. Likewise, MBEDTLS_SHA512_C enables both SHA-512 and SHA-384. The reason for this design is that SHA-256 and SHA-224 have essentially the same code but different constants, and likewise for SHA-512 and SHA-384.
What changed in Mbed TLS 3.0 is that there are now separate configuration options for each of the four SHA2 variants.
It is not possible yet to enable SHA-384 without SHA-512, SHA-224 without SHA-256 or SHA-256 without SHA-224. These are implementation limitations due to missing #ifdef in various places. We expect to lift these limitations in one of the next 3.x releases.
Best regards,
--
Gilles Peskine
Mbed TLS developer
On 19/07/2021 14:50, David Hu via mbed-tls wrote:
>
> Hi,
>
> �
>
> It seems that SHA224 is mandatory if SHA256 is selected, in Mbed TLS
> latest version, according to this new check below:
>
> �
>
> #if defined(MBEDTLS_SHA256_C) && !defined(MBEDTLS_SHA224_C)
>
> #error "MBEDTLS_SHA256_C defined without MBEDTLS_SHA224_C"
>
> #endif
>
> �
>
> May I know why SHA224 must be enabled with SHA256?
>
> Could you please point me to any reference/document?
>
> �
>
> Best regards,
>
> Hu Ziji
>
>