[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20161216204358.nlwifgcqnu6pitxs@thunk.org>
Date: Fri, 16 Dec 2016 15:43:58 -0500
From: Theodore Ts'o <tytso@....edu>
To: George Spelvin <linux@...encehorizons.net>
Cc: Jason@...c4.com, ak@...ux.intel.com, davem@...emloft.net,
David.Laight@...lab.com, djb@...yp.to, ebiggers3@...il.com,
hannes@...essinduktion.org, jeanphilippe.aumasson@...il.com,
kernel-hardening@...ts.openwall.com, linux-crypto@...r.kernel.org,
linux-kernel@...r.kernel.org, luto@...capital.net,
netdev@...r.kernel.org, tom@...bertland.com,
torvalds@...ux-foundation.org, vegard.nossum@...il.com
Subject: Re: [PATCH v5 1/4] siphash: add cryptographically secure PRF
On Fri, Dec 16, 2016 at 03:17:39PM -0500, George Spelvin wrote:
> > That's a nice analysis. Might one conclude from that that hsiphash is
> > not useful for our purposes? Or does it still remain useful for
> > network facing code?
>
> I think for attacks where the threat is a DoS, it's usable. The point
> is you only have to raise the cost to equal that of a packet flood.
> (Just like in electronic warfare, the best you can possibly do is force
> the enemy to use broadband jamming.)
>
> Hash collision attacks just aren't that powerful. The original PoC
> was against an application that implemented a hard limit on hash chain
> length as a DoS defense, which the attack then exploited to turn it into
> a hard DoS.
What should we do with get_random_int() and get_random_long()? In
some cases it's being used in performance sensitive areas, and where
anti-DoS protection might be enough. In others, maybe not so much.
If we rekeyed the secret used by get_random_int() and
get_random_long() frequently (say, every minute or every 5 minutes),
would that be sufficient for current and future users of these
interfaces?
- Ted
P.S. I'll note that my performance figures when testing changes to
get_random_int() were done on a 32-bit x86; Jason, I'm guessing your
figures were using a 64-bit x86 system?. I haven't tried 32-bit ARM
or smaller CPU's (e.g., mips, et. al.) that might be more likely to be
used on IoT devices, but I'm worried about those too, of course.
Powered by blists - more mailing lists
Confused about mailing lists and their use?
Read about mailing lists on Wikipedia
and check out these
guidelines on proper formatting of your messages.
