From mboxrd@z Thu Jan 1 00:00:00 1970 From: Herbert Xu Subject: Re: arp_hash Date: Mon, 23 Mar 2015 10:53:08 +1100 Message-ID: <20150322235308.GA9373@gondor.apana.org.au> References: <20150322215612.GA8274@gondor.apana.org.au> <20150322.185850.927485035002538859.davem@davemloft.net> <20150322230848.GA8989@gondor.apana.org.au> <20150322.195003.654000183854114521.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: eric.dumazet@gmail.com, netdev@vger.kernel.org, roland@purestorage.com To: David Miller Return-path: Received: from ringil.hengli.com.au ([178.18.16.133]:47201 "EHLO ringil.hengli.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751938AbbCVXxK (ORCPT ); Sun, 22 Mar 2015 19:53:10 -0400 Content-Disposition: inline In-Reply-To: <20150322.195003.654000183854114521.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: On Sun, Mar 22, 2015 at 07:50:03PM -0400, David Miller wrote: > > BTW I asked for feedback when I posted the patches which created this > situation, and the multiply with the random input was believed to have > sufficient entropy and not create a situation any worse, > asymptotically, than what we had beforehand. I know. I just didn't know at the time or I would have objected :) > Perhaps the ipv6 case can be improved, by using a u32 random input > for each u32 of the address being hashed. See my follow-up email. The multiplication is useless against an adversary, even if you multiply it against a secret odd value because there is a bit-to-bit correspondence between the key and the final hash value. Cheers, -- Email: Herbert Xu Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt