From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bmailout1.hostsharing.net (bmailout1.hostsharing.net [83.223.95.100]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 40C7D134C9; Sat, 2 Mar 2024 14:00:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=83.223.95.100 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709388007; cv=none; b=u9+wgqKkfEkZExqTXCpldrZ/Hc9Duif1h1f4tEp3zt5OPcBHms5x9HuUvqY9sVAc8woRRaxv0fK9bPzVFpNqiw9ePs43mrCswylRDtCLW3c4+OjaqoqgNy5eYFkg19Og7wuWPSp4GgnSfTvuS19kJFMj3hVUbuKnIDDzXhpfrPE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709388007; c=relaxed/simple; bh=5KUV8TszCFXRHWuLCnbMeuU3FypeFbMaSg6NAJFWi4Y=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=KFIRGAibNUzHGtA7D5xKv6IwEZ1C6gcKEgw8y6MiXPmshf6oSfQuVvbqNd7Zyo/4Nd2m+Yct0fi8+azWT+iYw2BGvMzZ4OhJuQM9Mo1N6oxZ2zH+/G3q6Qvk193RwEh30yc+ci+pcQE37zaMIGS/uD/jDK9ts0MTb4TCk1DkvLw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=wunner.de; spf=none smtp.mailfrom=h08.hostsharing.net; arc=none smtp.client-ip=83.223.95.100 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=wunner.de Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=h08.hostsharing.net Received: from h08.hostsharing.net (h08.hostsharing.net [IPv6:2a01:37:1000::53df:5f1c:0]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "*.hostsharing.net", Issuer "RapidSSL TLS RSA CA G1" (verified OK)) by bmailout1.hostsharing.net (Postfix) with ESMTPS id E7B0030008A00; Sat, 2 Mar 2024 15:00:01 +0100 (CET) Received: by h08.hostsharing.net (Postfix, from userid 100393) id C66D82DB1C; Sat, 2 Mar 2024 15:00:01 +0100 (CET) Date: Sat, 2 Mar 2024 15:00:01 +0100 From: Lukas Wunner To: Jarkko Sakkinen Cc: Stefan Berger , keyrings@vger.kernel.org, linux-crypto@vger.kernel.org, herbert@gondor.apana.org.au, davem@davemloft.net, linux-kernel@vger.kernel.org, saulo.alessandre@tse.jus.br Subject: Re: [PATCH v3 01/10] crypto: ecdsa - Convert byte arrays with key coordinates to digits Message-ID: <20240302140001.GA3095@wunner.de> References: <20240223204149.4055630-1-stefanb@linux.ibm.com> <20240223204149.4055630-2-stefanb@linux.ibm.com> <20240229091105.GA29363@wunner.de> Precedence: bulk X-Mailing-List: linux-crypto@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) On Fri, Mar 01, 2024 at 10:26:29PM +0200, Jarkko Sakkinen wrote: > On Thu Feb 29, 2024 at 4:57 PM EET, Stefan Berger wrote: > > > > > > On 2/29/24 04:11, Lukas Wunner wrote: > > > On Fri, Feb 23, 2024 at 03:41:40PM -0500, Stefan Berger wrote: > > >> +static inline void ecc_digits_from_bytes(const u8 *in, unsigned int nbytes, > > >> + u64 *out, unsigned int ndigits) > > >> +{ > > >> + unsigned int sz = ndigits << ECC_DIGITS_TO_BYTES_SHIFT; > > >> + u8 tmp[ECC_MAX_DIGITS << ECC_DIGITS_TO_BYTES_SHIFT]; > > >> + unsigned int o = sz - nbytes; > > >> + > > >> + memset(tmp, 0, o); > > >> + memcpy(&tmp[o], in, nbytes); > > >> + ecc_swap_digits(tmp, out, ndigits); > > >> +} > > > > > > Copying the whole key into tmp seems inefficient. You only need > > > special handling for the first few bytes of "in" (6 bytes in the > > > P521 case) and could use ecc_swap_digits() to convert the rest > > > of "in" directly to "out" without using tmp. > > > > > > So it would be sufficient to allocate the first digit on the stack, > > > memset + memcpy, then convert that to native byte order into "in[0]" > > > and use ecc_swap_digits() for the rest. > > > > > > And the special handling would be conditional on "!o", so is skipped > > > for existing curves. > > > > Thanks. It looks like this now: > > > > 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); > > This would be more stream-lined IMHO: > > unsigned int o = nbytes & 7; > unsigned int n = ndigits; > u64 msd = 0; > size_t i; > > if (o != 0) { > for (i = 0; i < o; i++) > msd = (msd << 8) | in[i]; > > out[--n] = msd; > } > > ecc_swap_digits(in, out, n); Maybe eliminate the for-loop as well? unsigned int o = nbytes & 7; u64 msd = 0; if (o != 0) { /* if key length is not a multiple of 64 bits (NIST P521) */ memcpy((u8 *)&msd + sizeof(msd) - o, in, o); out[--ndigits] = be64_to_cpu(msd); in += o; } ecc_swap_digits(in, out, ndigits);