The problem is if someone moves system time forward between app launches. The lockout period doesn't have to be all that precise, it just makes you wait for the next block, then 5, then 25, and so on. Using a well known time server over<span></span> https would also be a good option, but the wallet app already has the chain height anyway.<br>
<br>On Friday, July 25, 2014, Mike Hearn <<a href="mailto:mike@plan99.net">mike@plan99.net</a>> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">
Given that the speed at which the block chain advances is kind of unpredictable, I'd think it might be better to just record the time to disk when a PIN attempt is made and if you observe time going backwards, refuse to allow more attempts until it's advanced past the previous attempt.</div>
<div class="gmail_extra"><br><br><div class="gmail_quote">On Fri, Jul 25, 2014 at 7:56 AM, Aaron Voisine <span dir="ltr"><<a href="javascript:_e(%7B%7D,'cvml','voisine@gmail.com');" target="_blank">voisine@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
It's based on the block height, not the block's timestamp. If you have<br>
access to the device and the phone itself is not pin locked, then you<br>
can jailbreak it and get access to the wallet seed that way. A pin<br>
locked device however is reasonably secure as the filesystem is<br>
hardware aes encrypted to a combination of pin+uuid. This was just an<br>
easy way to prevent multiple pin guesses by changing system time in<br>
settings, so that isn't the weakest part of the security model.<br>
<span><font color="#888888"><br>
Aaron Voisine<br>
<a href="http://breadwallet.com" target="_blank">breadwallet.com</a><br>
</font></span><div><div><br>
<br>
On Thu, Jul 24, 2014 at 8:21 PM, William Yager <<a href="javascript:_e(%7B%7D,'cvml','will.yager@gmail.com');" target="_blank">will.yager@gmail.com</a>> wrote:<br>
> On Thu, Jul 24, 2014 at 10:39 PM, Gregory Maxwell <<a href="javascript:_e(%7B%7D,'cvml','gmaxwell@gmail.com');" target="_blank">gmaxwell@gmail.com</a>><br>
> wrote:<br>
>><br>
>><br>
>> Is breadwallet tamper resistant & zero on tamper hardware? otherwise<br>
>> this sounds like security theater.... I attach a debugger to the<br>
>> process (or modify the program) and ignore the block sourced time.<br>
>><br>
><br>
> It's an iOS application. I would imagine it is substantially more difficult<br>
> to attach to a process (which, at the very least, requires root, and perhaps<br>
> other things on iOS) than to convince the device to change its system time.<br>
><br>
> That said, the security benefits might not be too substantial.<br>
><br>
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</blockquote><br><br>-- <br><br>Aaron Voisine<br><a href="http://breadwallet.com" target="_blank">breadwallet.com</a><br>