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

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Message-ID: <20240229164810.GA7144@wunner.de>
Date: Thu, 29 Feb 2024 17:48:10 +0100
From: Lukas Wunner <lukas@...ner.de>
To: Stefan Berger <stefanb@...ux.ibm.com>
Cc: keyrings@...r.kernel.org, linux-crypto@...r.kernel.org,
	herbert@...dor.apana.org.au, davem@...emloft.net,
	linux-kernel@...r.kernel.org, saulo.alessandre@....jus.br
Subject: Re: [PATCH v3 01/10] crypto: ecdsa - Convert byte arrays with key
 coordinates to digits

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).

Otherwise LGTM, thanks!

Lukas