Adding new public key KEM API

[NIIBE Yutaka]

Werner Koch <wk at gnupg.org> wrote:
> On Thu, 19 Oct 2023 16:37, NIIBE Yutaka said:
>
>> gcry_error_t gcry_kem_decap (int algo,
>>                              const void *seckey,
>>                              const void *ciphertext,
>>                              void *shared_secret);
>
> I still don't feel comfortable without a size argument.

Assumption here (for lower level API) is:

	It's caller side (user of libgcrypt) which does static
	compile-time check against ALGO and the length of each
	byte-array.

        If not static, caller side can do run-time check, if needed,
        before the call.

Having a size argument would mean, 

	libgcrypt does run-time check of the length (for each call)

I wonder if this kind of run-time check in libgcrypt is useful in lower
level API.

I could imagine having an API offering static compile-time check.  In
this case, it would provide a macro something like gcry_kem_decap_check
which has length arguments.  The ABI is gcry_kem_decap.
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