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Subject: Re: [Bitcoin-development] Time
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Sorry, you're right. I'd have hoped a delay that doubles on failure each
time up to some max would be good enough, relying on the p2p network to
unlock a PIN feels weird, but I can't really quantify why or what's wrong
with it so I guess it's just me :-)


On Fri, Jul 25, 2014 at 4:45 PM, Aaron Voisine <voisine@gmail.com> wrote:

> 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 https would also be a good option, but the wallet
> app already has the chain height anyway.
>
>
> On Friday, July 25, 2014, Mike Hearn <mike@plan99.net> wrote:
>
>> 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.
>>
>>
>> On Fri, Jul 25, 2014 at 7:56 AM, Aaron Voisine <voisine@gmail.com> wrote:
>>
>>> It's based on the block height, not the block's timestamp. If you have
>>> access to the device and the phone itself is not pin locked, then you
>>> can jailbreak it and get access to the wallet seed that way. A pin
>>> locked device however is reasonably secure as the filesystem is
>>> hardware aes encrypted to a combination of pin+uuid. This was just an
>>> easy way to prevent multiple pin guesses by changing system time in
>>> settings, so that isn't the weakest part of the security model.
>>>
>>> Aaron Voisine
>>> breadwallet.com
>>>
>>>
>>> On Thu, Jul 24, 2014 at 8:21 PM, William Yager <will.yager@gmail.com>
>>> wrote:
>>> > On Thu, Jul 24, 2014 at 10:39 PM, Gregory Maxwell <gmaxwell@gmail.com>
>>> > wrote:
>>> >>
>>> >>
>>> >> Is breadwallet tamper resistant & zero on tamper hardware? otherwise
>>> >> this sounds like security theater.... I attach a debugger to the
>>> >> process (or modify the program) and ignore the block sourced time.
>>> >>
>>> >
>>> > It's an iOS application. I would imagine it is substantially more
>>> difficult
>>> > to attach to a process (which, at the very least, requires root, and
>>> perhaps
>>> > other things on iOS) than to convince the device to change its system
>>> time.
>>> >
>>> > That said, the security benefits might not be too substantial.
>>> >
>>> >
>>> ------------------------------------------------------------------------------
>>> > Want fast and easy access to all the code in your enterprise? Index and
>>> > search up to 200,000 lines of code with a free copy of Black Duck
>>> > Code Sight - the same software that powers the world's largest code
>>> > search on Ohloh, the Black Duck Open Hub! Try it now.
>>> > http://p.sf.net/sfu/bds
>>> > _______________________________________________
>>> > Bitcoin-development mailing list
>>> > Bitcoin-development@lists.sourceforge.net
>>> > https://lists.sourceforge.net/lists/listinfo/bitcoin-development
>>> >
>>>
>>>
>>> ------------------------------------------------------------------------------
>>> Want fast and easy access to all the code in your enterprise? Index and
>>> search up to 200,000 lines of code with a free copy of Black Duck
>>> Code Sight - the same software that powers the world's largest code
>>> search on Ohloh, the Black Duck Open Hub! Try it now.
>>> http://p.sf.net/sfu/bds
>>> _______________________________________________
>>> Bitcoin-development mailing list
>>> Bitcoin-development@lists.sourceforge.net
>>> https://lists.sourceforge.net/lists/listinfo/bitcoin-development
>>>
>>
>>
>
> --
>
> Aaron Voisine
> breadwallet.com
>

--001a11332c8eaae56e04ff06b618
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<div dir=3D"ltr">Sorry, you&#39;re right. I&#39;d have hoped a delay that d=
oubles on failure each time up to some max would be good enough, relying on=
 the p2p network to unlock a PIN feels weird, but I can&#39;t really quanti=
fy why or what&#39;s wrong with it so I guess it&#39;s just me :-)</div>
<div class=3D"gmail_extra"><br><br><div class=3D"gmail_quote">On Fri, Jul 2=
5, 2014 at 4:45 PM, Aaron Voisine <span dir=3D"ltr">&lt;<a href=3D"mailto:v=
oisine@gmail.com" target=3D"_blank">voisine@gmail.com</a>&gt;</span> wrote:=
<br><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-lef=
t:1px #ccc solid;padding-left:1ex">
The problem is if someone moves system time forward between app launches. T=
he lockout period doesn&#39;t have to be all that precise, it just makes yo=
u wait for the next block, then 5, then 25, and so on. Using a well known=
=C2=A0time server over<span></span>=C2=A0https would also be a good option,=
 but the wallet app already has the chain height anyway.<div class=3D"HOEnZ=
b">
<div class=3D"h5"><br>
<br>On Friday, July 25, 2014, Mike Hearn &lt;<a href=3D"mailto:mike@plan99.=
net" target=3D"_blank">mike@plan99.net</a>&gt; wrote:<br><blockquote class=
=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padd=
ing-left:1ex">
<div dir=3D"ltr">
Given that the speed at which the block chain advances is kind of unpredict=
able, I&#39;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 a=
llow more attempts until it&#39;s advanced past the previous attempt.</div>


<div class=3D"gmail_extra"><br><br><div class=3D"gmail_quote">On Fri, Jul 2=
5, 2014 at 7:56 AM, Aaron Voisine <span dir=3D"ltr">&lt;<a>voisine@gmail.co=
m</a>&gt;</span> wrote:<br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex">
It&#39;s based on the block height, not the block&#39;s timestamp. If you h=
ave<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&#39;t the weakest part of the security model.<br>
<span><font color=3D"#888888"><br>
Aaron Voisine<br>
<a href=3D"http://breadwallet.com" target=3D"_blank">breadwallet.com</a><br=
>
</font></span><div><div><br>
<br>
On Thu, Jul 24, 2014 at 8:21 PM, William Yager &lt;<a>will.yager@gmail.com<=
/a>&gt; wrote:<br>
&gt; On Thu, Jul 24, 2014 at 10:39 PM, Gregory Maxwell &lt;<a>gmaxwell@gmai=
l.com</a>&gt;<br>
&gt; wrote:<br>
&gt;&gt;<br>
&gt;&gt;<br>
&gt;&gt; Is breadwallet tamper resistant &amp; zero on tamper hardware? oth=
erwise<br>
&gt;&gt; this sounds like security theater.... I attach a debugger to the<b=
r>
&gt;&gt; process (or modify the program) and ignore the block sourced time.=
<br>
&gt;&gt;<br>
&gt;<br>
&gt; It&#39;s an iOS application. I would imagine it is substantially more =
difficult<br>
&gt; to attach to a process (which, at the very least, requires root, and p=
erhaps<br>
&gt; other things on iOS) than to convince the device to change its system =
time.<br>
&gt;<br>
&gt; That said, the security benefits might not be too substantial.<br>
&gt;<br>
</div></div><div><div>&gt; ------------------------------------------------=
------------------------------<br>
&gt; Want fast and easy access to all the code in your enterprise? Index an=
d<br>
&gt; search up to 200,000 lines of code with a free copy of Black Duck<br>
&gt; Code Sight - the same software that powers the world&#39;s largest cod=
e<br>
&gt; search on Ohloh, the Black Duck Open Hub! Try it now.<br>
&gt; <a href=3D"http://p.sf.net/sfu/bds" target=3D"_blank">http://p.sf.net/=
sfu/bds</a><br>
&gt; _______________________________________________<br>
&gt; Bitcoin-development mailing list<br>
&gt; <a>Bitcoin-development@lists.sourceforge.net</a><br>
&gt; <a href=3D"https://lists.sourceforge.net/lists/listinfo/bitcoin-develo=
pment" target=3D"_blank">https://lists.sourceforge.net/lists/listinfo/bitco=
in-development</a><br>
&gt;<br>
<br>
---------------------------------------------------------------------------=
---<br>
Want fast and easy access to all the code in your enterprise? Index and<br>
search up to 200,000 lines of code with a free copy of Black Duck<br>
Code Sight - the same software that powers the world&#39;s largest code<br>
search on Ohloh, the Black Duck Open Hub! Try it now.<br>
<a href=3D"http://p.sf.net/sfu/bds" target=3D"_blank">http://p.sf.net/sfu/b=
ds</a><br>
_______________________________________________<br>
Bitcoin-development mailing list<br>
<a>Bitcoin-development@lists.sourceforge.net</a><br>
<a href=3D"https://lists.sourceforge.net/lists/listinfo/bitcoin-development=
" target=3D"_blank">https://lists.sourceforge.net/lists/listinfo/bitcoin-de=
velopment</a><br>
</div></div></blockquote></div><br></div>
</blockquote><br><br></div></div><span class=3D"HOEnZb"><font color=3D"#888=
888">-- <br><br>Aaron Voisine<br><a href=3D"http://breadwallet.com" target=
=3D"_blank">breadwallet.com</a><br>
</font></span></blockquote></div><br></div>

--001a11332c8eaae56e04ff06b618--