Date: Sun, 13 Mar 2011 21:06:17 +0000 From: Miguel Lopes Santos Ramos <mbox@miguel.ramos.name> To: Peter Jeremy <peterjeremy@acm.org> Cc: freebsd-security@freebsd.org Subject: Re: It's not possible to allow non-OPIE logins only from trusted networks Message-ID: <1300050377.5900.12.camel@w500.local> In-Reply-To: <20110313204054.GA5392@server.vk2pj.dyndns.org> References: <1299682310.17149.24.camel@w500.local> <alpine.BSF.2.00.1103100147350.1891@qvfongpu.qngnvk.ybpny> <1299769253.20266.23.camel@w500.local> <2E5C0CE8-4F70-4A4D-A91D-3274FD394C80@elvandar.org> <1299784361.18199.4.camel@w500.local> <20110310202653.GG9421@shame.svkt.org> <1299798547.20831.59.camel@w500.local> <20110313204054.GA5392@server.vk2pj.dyndns.org>
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Seg, 2011-03-14 =C3=A0s 07:40 +1100, Peter Jeremy escreveu: > On 2011-Mar-10 23:09:07 +0000, Miguel Lopes Santos Ramos <mbox@miguel.ram= os.name> wrote: > >- The objection on S/KEY on that wiki page, that it's possible to > >compute all previous passwords, is a bit odd, since past passwords won't > >be used anymore. >=20 > One weakness of S/KEY and OPIE is that if an attacker finds the > password (response) for sequence N then they can trivially determine > the response for any sequence > N. This could occur if (eg) you have > a printout of OPIE keys and are just crossing them off (which was a > common recommendation prior to smart phones etc) - an attacker just > needs to memorise the lowest N and response. Ok, admittedly, it took me a while to see in what way that could be a weekness. It's a bit like hoping for a little remaining security after the password list was compromised. Personally, I would still prefer OPIE to OTPW. A calculator beats a list (for me). For instance, around here many banks provide little matrix cards from which they then ask for the numbers by row/column for access to some operations on home banking. Now, with banks, physical security matters. What do I do? None of the choices is good: if I hide the card, I can't use it... (obviously I encrypt the content with PGP and destroy the card). So, I think there's an elegance to the S/KEY solution that OTPW doesn't have. --=20 Miguel Ramos <mbox@miguel.ramos.name> PGP A006A14C
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