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Date:   Mon, 10 Feb 2020 10:36:21 -0800
From:   Eric Biggers <ebiggers@kernel.org>
To:     Ken Goldman <kgold@linux.ibm.com>
Cc:     "Van Leeuwen, Pascal" <pvanleeuwen@rambus.com>,
        James Bottomley <James.Bottomley@HansenPartnership.com>,
        Ken Goldman <kgold@linux.ibm.com>,
        Tianjia Zhang <tianjia.zhang@linux.alibaba.com>,
        herbert@gondor.apana.org.au, davem@davemloft.net,
        zohar@linux.ibm.com, dmitry.kasatkin@gmail.com, jmorris@namei.org,
        serge@hallyn.com, linux-crypto@vger.kernel.org,
        linux-integrity@vger.kernel.org,
        linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] crypto: sm3 - add a new alias name sm3-256
Message-ID: <20200210183620.GA137710@gmail.com>
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On Mon, Feb 10, 2020 at 01:02:42PM -0500, Ken Goldman wrote:
> On 2/10/2020 12:01 PM, Van Leeuwen, Pascal wrote:
> > Well, the current specification surely doesn't define anything else and is
> > already over a decade old. So what would be the odds that they add a
> > different blocksize variant_now_  AND still call that SM3-something?
> 
> I just got a note from a cryptographer who said there were discussions last
> year about a future SM3 with 512 bit output.
> 
> Given that, why not plan ahead and use sm3-256?  Is there any downside?
> Is the cost any more than 4 bytes in some source code?

If renaming sm3 to sm3-256 in the crypto API, no.  If adding sm3-256 alongside
sm3, then yes there is a cost to that because from the crypto API's perspective
they will be separate algorithms that each need to be registered, tested, etc.

- Eric