<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div><br><br>dol@ с iPad</div><div><br>1 февр. 2016 г., в 21:24, Warren Kumari <<a href="mailto:warren@kumari.net">warren@kumari.net</a>> написал(а):<br><br></div><blockquote type="cite"><div><div dir="ltr"><br><br><div class="gmail_quote"><div dir="ltr">On Mon, Feb 1, 2016 at 1:07 PM Fredrik Thulin <<a href="mailto:fredrik@thulin.net">fredrik@thulin.net</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><u></u>
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<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">Hi</p>
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<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">The suggestion has been made to remove the external RTC chip currently on the Alpha schematics, and instead just rely on the RTC inside the ARM.</p>
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<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">The end of the discussion last time was Basil asking which chip was more likely to be possible to tamper with. I think the answer is "they are both pretty easy to tamper with if you have code execution privileges in the ARM".</p></div></blockquote><div><br></div><div>Probably a stupid idea, but what about using *both*? If the time between the 2 RTCs is >N, assume some shenanigans? </div></div></div></div></blockquote>What for?<div>What is threat model and adversary model? </div><div>We can evaluate the necessity of any countermeasures only against well-defined threat model. <br><blockquote type="cite"><div><div dir="ltr"><div class="gmail_quote"><div>Based on how quickly RTCs seems to drift, this may end up with lots of false positives though....</div><div><br></div><div>W</div><div><br></div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="font-family:'monospace';font-size:9pt;font-weight:400;font-style:normal">
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<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">OK to remove external chip? The internal RTC is likely easier to interface with, so it saves us engineering time.</p>
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<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">/Fredrik</p>
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