Date: Tue, 15 Mar 2011 21:02:56 +0000 From: Miguel Lopes Santos Ramos <mbox@miguel.ramos.name> To: RW <rwmaillists@googlemail.com>, Dag-Erling =?ISO-8859-1?Q?Sm=F8rgrav?= <des@des.no> Cc: freebsd-security@freebsd.org Subject: Re: It's not possible to allow non-OPIE logins only from trusted networks Message-ID: <1300222976.7909.19.camel@w500.local> In-Reply-To: <20110313220552.5b79de13@gumby.homeunix.com> 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> <1300050377.5900.12.camel@w500.local> <20110313220552.5b79de13@gumby.homeunix.com>
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Dom, 2011-03-13 às 22:05 +0000, RW escreveu: > On Sun, 13 Mar 2011 21:06:17 +0000 > Miguel Lopes Santos Ramos <mbox@miguel.ramos.name> wrote: > > 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. > > It means they can compute keys that they already have on the printout > plus obsolete keys. In what sense is that a weakness? Yes, also in my opinion that is not a weakness. I was trying to see the thing through the perspective of those who call it a weakness (it was a reply). Let's call it a non-strongness. The point that I took a while to see and which I think it's the reason why they say it's a weakness, is that if an attacker only came to possess a future password (one with a lower sequence number), then he can trivially compute all previous passwords. This is a non-strongness in the sense that if it weren't so, he might never get a chance of using that password. Ter, 2011-03-15 às 11:43 +0100, Dag-Erling Smørgrav escreveu: Miguel Lopes Santos Ramos <mbox@miguel.ramos.name> writes: > > 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. > > OPIE is not designed to protect against a stolen password list; it is > designed to protect against replay attacks. So I understand. That's why my words were such a faible concession to that point of view. The wikipedia page for OTPW actually states that as a disadvantage of OPIE, making several times the point that OTPW is resistent to the case of a stolen password list. They also make the questionable argument of a paper being more portable than a calculator, which I also understand but don't agree, because a calculator can be "transported" over the Internet easily. I've been using OPIE for several years now, and I don't think OTPW would fit my usage patterns. Sorry for cross-thread posting. -- Miguel Ramos <mbox@miguel.ramos.name> PGP A006A14Chelp
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