Re: [PATCH v3 01/10] crypto: ecdsa - Convert byte arrays with key coordinates to digits

Stefan Berger
2024-02-29T17:20:21Z

On 2/29/24 11:48, Lukas Wunner wrote:
> On Thu, Feb 29, 2024 at 09:57:30AM -0500, Stefan Berger wrote:
>> static inline void ecc_digits_from_bytes(const u8 *in, unsigned int nbytes,
>> u64 *out, unsigned int ndigits)
>> {
>> unsigned int o = nbytes & 7;
>> u64 msd = 0;
>> size_t i;
>>
>> if (o == 0) {
>> ecc_swap_digits(in, out, ndigits);
>> } else {
>> for (i = 0; i < o; i++)
>> msd = (msd << 8) | in[i];
>> out[ndigits - 1] = msd;
>> ecc_swap_digits(&in[o], out, ndigits - 1);
>> }
>> }
>
> Might be beneficial to add a code comment explaining the else-branch
> is for curves with key length not a multiple of 64 bits (such as NIST P521).

Will do. I am also using this here now since it's safer:
ecc_swap_digits(&in[o], out, (nbytes - o) >> 3);

Stefan

>
> Otherwise LGTM, thanks!
>
> Lukas