From: David Laight <David.Laight@ACULAB.COM>
To: 'George Spelvin' <linux@sciencehorizons.net>,
"ak@linux.intel.com" <ak@linux.intel.com>,
"davem@davemloft.net" <davem@davemloft.net>,
"ebiggers3@gmail.com" <ebiggers3@gmail.com>,
"hannes@stressinduktion.org" <hannes@stressinduktion.org>,
"Jason@zx2c4.com" <Jason@zx2c4.com>,
"jeanphilippe.aumasson@gmail.com"
<jeanphilippe.aumasson@gmail.com>,
"kernel-hardening@lists.openwall.com"
<kernel-hardening@lists.openwall.com>,
"linux-crypto@vger.kernel.org" <linux-crypto@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"luto@amacapital.net" <luto@amacapital.net>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"tom@herbertland.com" <tom@herbertland.com>,
"torvalds@linux-foundation.org" <torvalds@linux-foundation.org>,
"tytso@mit.edu" <tytso
Cc: "djb@cr.yp.to" <djb@cr.yp.to>
Subject: RE: [PATCH v5 1/4] siphash: add cryptographically secure PRF
Date: Fri, 16 Dec 2016 17:06:57 +0000 [thread overview]
Message-ID: <063D6719AE5E284EB5DD2968C1650D6DB0241238@AcuExch.aculab.com> (raw)
In-Reply-To: <20161215232840.22459.qmail@ns.sciencehorizons.net>
From: George Spelvin
> Sent: 15 December 2016 23:29
> > If a halved version of SipHash can bring significant performance boost
> > (with 32b words instead of 64b words) with an acceptable security level
> > (64-bit enough?) then we may design such a version.
>
> I was thinking if the key could be pushed to 80 bits, that would be nice,
> but honestly 64 bits is fine. This is DoS protection, and while it's
> possible to brute-force a 64 bit secret, there are more effective (DDoS)
> attacks possible for the same cost.
A 32bit hash would also remove all the issues about the alignment
of IP addresses (etc) on 64bit systems.
> (I'd suggest a name of "HalfSipHash" to convey the reduced security
> effectively.)
>
> > Regarding output size, are 64 bits sufficient?
>
> As a replacement for jhash, 32 bits are sufficient. It's for
> indexing an in-memory hash table on a 32-bit machine.
It is also worth remembering that if the intent is to generate
a hash table index (not a unique fingerprint) you will always
get collisions on the final value.
Randomness could still give overlong hash chains - which might
still need rehashing with a different key.
David
next prev parent reply other threads:[~2016-12-16 17:07 UTC|newest]
Thread overview: 92+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-15 20:29 [PATCH v5 0/4] The SipHash Patchset Jason A. Donenfeld
2016-12-15 20:30 ` [PATCH v5 1/4] siphash: add cryptographically secure PRF Jason A. Donenfeld
2016-12-15 22:42 ` George Spelvin
2016-12-15 23:00 ` Jean-Philippe Aumasson
2016-12-15 23:28 ` George Spelvin
2016-12-16 17:06 ` David Laight [this message]
2016-12-16 17:09 ` Jason A. Donenfeld
2016-12-16 3:46 ` George Spelvin
2016-12-16 8:08 ` Jean-Philippe Aumasson
2016-12-16 12:39 ` Jason A. Donenfeld
2016-12-16 13:22 ` Jean-Philippe Aumasson
2016-12-16 15:51 ` Jason A. Donenfeld
2016-12-16 17:36 ` George Spelvin
2016-12-16 18:00 ` Jason A. Donenfeld
2016-12-16 20:17 ` George Spelvin
2016-12-16 20:43 ` Theodore Ts'o
2016-12-16 22:13 ` George Spelvin
2016-12-16 22:15 ` Andy Lutomirski
2016-12-16 22:18 ` Jason A. Donenfeld
2016-12-16 23:44 ` George Spelvin
2016-12-17 1:39 ` Jason A. Donenfeld
2016-12-17 2:15 ` George Spelvin
2016-12-17 15:41 ` Theodore Ts'o
2016-12-17 16:14 ` Jeffrey Walton
2016-12-19 17:21 ` [kernel-hardening] " Jason A. Donenfeld
2016-12-17 12:42 ` George Spelvin
2016-12-16 20:39 ` Jason A. Donenfeld
2016-12-16 19:47 ` Tom Herbert
2016-12-16 20:41 ` George Spelvin
2016-12-16 20:57 ` Tom Herbert
2016-12-16 20:44 ` Daniel Micay
2016-12-16 21:09 ` [kernel-hardening] " Jason A. Donenfeld
2016-12-17 15:21 ` George Spelvin
2016-12-19 14:14 ` David Laight
2016-12-19 18:10 ` George Spelvin
2016-12-19 20:18 ` Jean-Philippe Aumasson
2016-12-16 2:14 ` kbuild test robot
2016-12-17 14:55 ` Jeffrey Walton
2016-12-19 17:08 ` Jason A. Donenfeld
2016-12-19 17:19 ` Jean-Philippe Aumasson
2016-12-15 20:30 ` [PATCH v5 2/4] siphash: add Nu{32,64} helpers Jason A. Donenfeld
2016-12-16 10:39 ` David Laight
2016-12-16 15:44 ` George Spelvin
2016-12-15 20:30 ` [PATCH v5 3/4] secure_seq: use SipHash in place of MD5 Jason A. Donenfeld
2016-12-16 9:59 ` David Laight
2016-12-16 15:57 ` Jason A. Donenfeld
2016-12-15 20:30 ` [PATCH v5 4/4] random: " Jason A. Donenfeld
2016-12-16 3:03 ` [PATCH v6 0/5] The SipHash Patchset Jason A. Donenfeld
2016-12-16 3:03 ` [PATCH v6 1/5] siphash: add cryptographically secure PRF Jason A. Donenfeld
2016-12-16 3:03 ` [PATCH v6 2/5] secure_seq: use SipHash in place of MD5 Jason A. Donenfeld
2016-12-16 3:03 ` [PATCH v6 3/5] random: " Jason A. Donenfeld
2016-12-16 21:31 ` Andy Lutomirski
2016-12-16 3:03 ` [PATCH v6 4/5] md5: remove from lib and only live in crypto Jason A. Donenfeld
2016-12-16 3:03 ` [PATCH v6 5/5] syncookies: use SipHash in place of SHA1 Jason A. Donenfeld
2016-12-21 23:02 ` [PATCH v7 0/6] The SipHash Patchset Jason A. Donenfeld
2016-12-21 23:02 ` [PATCH v7 1/6] siphash: add cryptographically secure PRF Jason A. Donenfeld
2016-12-22 1:40 ` Stephen Hemminger
2016-12-21 23:02 ` [PATCH v7 2/6] secure_seq: use SipHash in place of MD5 Jason A. Donenfeld
2016-12-21 23:02 ` [PATCH v7 3/6] random: " Jason A. Donenfeld
2016-12-21 23:13 ` Jason A. Donenfeld
2016-12-21 23:42 ` Andy Lutomirski
2016-12-22 2:07 ` Hannes Frederic Sowa
2016-12-22 2:09 ` Andy Lutomirski
2016-12-22 2:49 ` Jason A. Donenfeld
2016-12-22 3:12 ` Jason A. Donenfeld
2016-12-22 5:41 ` Theodore Ts'o
2016-12-22 6:03 ` [kernel-hardening] " Jason A. Donenfeld
2016-12-22 15:58 ` Theodore Ts'o
2016-12-22 16:16 ` Jason A. Donenfeld
2016-12-22 16:30 ` [kernel-hardening] " Theodore Ts'o
2016-12-22 16:36 ` Jason A. Donenfeld
2016-12-22 12:47 ` Hannes Frederic Sowa
2016-12-22 13:10 ` [kernel-hardening] " Jason A. Donenfeld
2016-12-22 15:05 ` Hannes Frederic Sowa
2016-12-22 15:12 ` Jason A. Donenfeld
2016-12-22 15:29 ` Jason A. Donenfeld
2016-12-22 15:33 ` Hannes Frederic Sowa
2016-12-22 15:41 ` [kernel-hardening] " Jason A. Donenfeld
2016-12-22 15:51 ` Hannes Frederic Sowa
2016-12-22 15:53 ` [kernel-hardening] " Jason A. Donenfeld
2016-12-22 15:54 ` Theodore Ts'o
2016-12-22 18:08 ` [kernel-hardening] " Hannes Frederic Sowa
2016-12-22 18:13 ` Jason A. Donenfeld
2016-12-22 19:50 ` [kernel-hardening] " Theodore Ts'o
2016-12-22 2:31 ` Jason A. Donenfeld
2016-12-21 23:02 ` [PATCH v7 4/6] md5: remove from lib and only live in crypto Jason A. Donenfeld
2016-12-21 23:02 ` [PATCH v7 5/6] syncookies: use SipHash in place of SHA1 Jason A. Donenfeld
2016-12-21 23:02 ` [PATCH v7 6/6] siphash: implement HalfSipHash1-3 for hash tables Jason A. Donenfeld
2016-12-22 0:46 ` Andi Kleen
2016-12-16 20:43 [PATCH v5 1/4] siphash: add cryptographically secure PRF Jason A. Donenfeld
2016-12-16 20:49 Jason A. Donenfeld
2016-12-16 21:25 ` George Spelvin
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