linux-kernel - Re: [RFC 3/7] lib: add rocksoft model crc64

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20220125153950.GB1683949@dhcp-10-100-145-180.wdc.com>
Date:   Tue, 25 Jan 2022 07:39:50 -0800
From:   Keith Busch <kbusch@...nel.org>
To:     Eric Biggers <ebiggers@...nel.org>
Cc:     linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-block@...r.kernel.org, axboe@...nel.dk, hch@....de,
        martin.petersen@...cle.com, colyli@...e.de, arnd@...db.de
Subject: Re: [RFC 3/7] lib: add rocksoft model crc64

On Mon, Jan 24, 2022 at 09:10:38PM -0800, Eric Biggers wrote:
> On Mon, Jan 24, 2022 at 08:01:03AM -0800, Keith Busch wrote:
> > Since this model reflects inputs and outputs, a helper table and
> > function are added to reverse bits of 8 and 64 bit values.
> 
> That's a silly way to do a bit-reflected CRC.  The proper way to do it is to
> reflect the bytes too, so that the bits and bytes are ordered consistently, so
> explicitly reflecting the bits isn't needed.  Most CRC-32's are bit-reflected,
> and they are usually implemented this way.  E.g., see crc32_le() in lib/crc32.c.
> 
> Here's a Python script that shows that the Rocksoft CRC-64 can be computed
> without explicitly reversing the bits.  It passes the tests from your patch 4:

Thanks for the tip! I'll use that for the next version.