Comments in-line<br><br><div><span class="gmail_quote">On 7/31/07, <b class="gmail_sendername">Jameson Chema Quinn</b> <<a href="mailto:jquinn@cs.oberlin.edu">jquinn@cs.oberlin.edu</a>> wrote:</span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div><span class="q"></span><span class="q"><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">You're drawing a pretty fine line trying to separate the two. The only
<br>reason they would think it is not "plausible" that John is asking for<br>a confirmation of himself (essentially) is if Jane (the person being<br>asked for confirmation) has some reason to explicitly doubt that John
<br>isn't asking. Either by asking him outright, knowing that he is not at<br>his computer, or similar absolute means. Otherwise, being asked to<br>confirm that she has John's key could be done by any number of people,
<br>and if her gauge is "it is plausible that he might be doing this" is a<br>vague guideline.</blockquote></span><div><br>Yes. So she essentially always says "yes". But next time she sees John, she (or someone else who happened to notice the unobtrusive announcement) says, "so how did you lose your laptop, tell me the story" and if he says "huh?" people start to suspect things.
</div></div></blockquote><div><br>The problem comes down to that by splitting up your key (either in a simple half-n-half system, or a more rigid/proper 'secret sharing' (see below) system, is that either way, the N peers that you split up your private key have the potential to get at your private documents. Relying on some type of hardware-level (UUID, or similar) component alongside the private key should be able to get around this. Moving to a new laptop would require the social process (asking a teacher to update the mapping of student->laptop pairing previously talked about). Combining these two steps should create a secure scheme that relies on your peers and your teachers to not conspire against you but that keeps either individual party from being able to snoop on you without raising big red 'what the hell are you doing' flags.
<br></div><br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><div><div>With a million laptops per country, there's a big difference between "they can get your data whenever they want to, and you'll never know" and "they can get your data
99.9% of whenever they want to, but even if they do, there's a 5% chance you'll find out".
</div></div></blockquote><div><br>As mentioned, this is not a gen-1 feature, but a secret sharing scheme [1] like this is pretty reasonable. Note that we can have an 'N-friends I trust', or even simply 'N-peers I know', and have it reliably safe to distribute my private key amongst them. Wikipedia has a great article about this, in fact. This allows for a secure means of key distribution, but also allows for
<br></div><br>[1] <a href="http://en.wikipedia.org/wiki/Secret_splitting">http://en.wikipedia.org/wiki/Secret_splitting</a><br><br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div><div><span class="e" id="q_1141d558566ae6e1_11"><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">> > > Obviously, a committed big-brother could still twist two kids' arms and
<br>> convince the rest to ignore the message. But that doesn't scale well to<br>> stealing EVERYONE's data and mining it, which is the real threat.<br>> ><br>> > But they wouldn't need to get everyone. The handful of kids they
<br>> > choose to strong arm (or coerce or 'borrow' the laptops of, or analyze<br>> > while repairing, or, or, or...) would be--using your system--carrying<br>> > 1/2 of another person's key. Several halves, in fact. Get a large
<br>> > enough sample, then you are getting the private keys of children that<br>> > they didn't directly interact with. Would this be easy for a million<br>> > kids at once? Probably not. But at that point, you are also assuming a
<br>> > great number of things about your government, like that they didn't<br>> > install keyloggers on the XOs before shipping them out or during<br>> > repair.<br>><br>> Yes, true, a committed evildoer with the key-copies from 60% of the laptops
<br>> would be able to snoop on 1-((1-0.60)cubed) = 93.6% of the files on average.<br>> With 90%, they'd get 99.9%. Still, that is a lot of work to just get to<br>> EXACTLY where they would be from the start in your scenario. Also, remember
<br>> that if any kid puts a password on their laptop, the stolen-during-repair<br>> scenario should be preventable (assuming that there is a way to put it in<br>> unlocked "repair mode" which only protects the securest data like keys).
<br>><br>> Also, Bitfrost prevents keyloggers.<br><br>This should be clarified: Bitfrost *does not* stop keyloggers. And<br>this is important. Bitfrost *explicitly* makes it possible (though, it<br>is an abuse of the authority on the deepest level) for OLPC or the
<br>country to install software that can bypass security restrictions.<br>Keyloggers included. This can either work inside of Bitfrost or simply<br>ignore it entirely. Both the country and OLPC are able to sign binary<br>
patches that are installed on the machine. Kernel modules, X11, Sugar,<br>DBus, the firmware. You name it. Heck, they could even install a<br>hardware keylogger.<br><br>If they touch it, they own it. If they can install software on it,
<br>they own it. If they can convince you to install software on it, they<br>own it. [1] (Ironic that it is a microsoft site, I know)</blockquote></span></div><div><br>OK, granted. But here I live in Guatemala - a pretty run-of-the-mill 3rd world country. Not as well-run as Mexico (or another 20 like it) but much better-off than Haiti or most of Africa. Genocide in the living memory of many people I know, a government you can't trust, the policeman is NOT your friend, but no ongoing conflict. And I'm pretty sure that the government couldn't get it together enough to install special snooping software if they wanted, and 100% sure they couldn't do it without getting caught. And the more capacity to create such snoopers a country has, the more savvy its citizens are about catching it. Even in, say, Colombia, with plenty of motive and help from super CIA advisors, the chances of getting caught would be more than half. And so fine: they'd tough it out, say "the war on the narcos is more important than your privacy", and people might accept that. But at least they'd have the conversation.
</div></div></blockquote><div><br>Agreed <br></div><br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><div><span class="q"><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
As mentioned above you are trusting that the users probed for<br>
information are aware enough to know that they are being probed and<br>not benignly misguided, outright tricked or otherwise worked around.<br>This is part of the limitation of not relying on the XO owner for a<br>token (password/passphrase, etc).
</blockquote></span><div><br>Most will not be aware. It only takes a few - and it only takes a possibility to make the snooper think twice.<br><br>3. Second level of backups - regional or peer-to-peer with the servers?<br>
</div>
<br>I think we're talking across each other. My point is: <br>A: a regional backup is only good for restoring the school server, because you can't rely on the local internet connection at the moment the kid wants their old data. There is no file that's you want to throw away locally that's still worth keeping regionally (after all, you have at least 3-5 gigs per kid at the local level, that's plenty.
</div></blockquote><div><br>Agreed. Regional/Global backup is really about ensuring that we can restore a given school server. I don't see the school server realistically ever running out of space for a comprehensive storing of each child's data. If it does, access to the R/G backup is available, and the liklihood that you (1) need such a document that is sufficiently old (2) your school server is maxed on storage and does not have it locally stored and (3) your satellite is down is an exceptionally uncommon niche case.
<br><br>Sorry for the delayed reply. Cheers! <br></div><br></div>-- <br>Michael Burns * Intern<br> One Laptop Per Child