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RIOT-OS
sys/psa_crypto: correct use of (ECDSA) key_bits
Contribution description
The key_bits that are part of the psa_key_attributes_t are restricted to certain values in the PSA specification. An example is PSA_ECC_FAMILY_SECP_R1, which allows for key_bits = 256, among others.
However, in https://github.com/RIOT-OS/RIOT/blob/master/examples/psa_crypto/example_ecdsa_p256.c#L91, key_bits was set to the size of the exported key, which at least for PSA_ECC_FAMILY_SECP_R1 doesn't match the expected key_bits (as it is defined here to be 1+2*key_bits).
Fixing this revealed a unnecessary computation of the curve_bits, which actually match the key_bits according to the specification. Removed the respective macros and adapted all their usage.
Testing procedure
CI should suffice to see that compilation and the tests succeed.
Issues/PRs references
Fixes #20468.
Draft since blocked by #20545: the change in examples/psa_crypto/example_ecdsa_p256.c needs to be copied to tests/sys/psa_crypto_ecdsa*/example_ecdsa_p256.c
Murdock results
:heavy_check_mark: PASSED
15e48f0cf3aeeb1ba2b31bd1c2782b2e96fa29f3 sys/psa_crypto: correct use of (ECDSA) key_bits
| Success | Failures | Total | Runtime |
|---|---|---|---|
| 10083 | 0 | 10083 | 13m:20s |
