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Subject: Re: [Bitcoin-development] Time
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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
> <javascript:_e(%7B%7D,'cvml','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
>> <javascript:_e(%7B%7D,'cvml','will.yager@gmail.com');>> wrote:
>> > On Thu, Jul 24, 2014 at 10:39 PM, Gregory Maxwell <gmaxwell@gmail.com
>> <javascript:_e(%7B%7D,'cvml','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
>> <javascript:_e(%7B%7D,'cvml','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
>> <javascript:_e(%7B%7D,'cvml','Bitcoin-development@lists.sourceforge.net');>
>> https://lists.sourceforge.net/lists/listinfo/bitcoin-development
>>
>
>
--
Aaron Voisine
breadwallet.com
--e89a8ff242598d5f8304ff05a03b
Content-Type: text/html; charset=UTF-8
Content-Transfer-Encoding: quoted-printable
The problem is if someone moves system time forward between app launches. T=
he lockout period doesn'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.<br>
<br>On Friday, July 25, 2014, Mike Hearn <<a href=3D"mailto:mike@plan99.=
net">mike@plan99.net</a>> wrote:<br><blockquote class=3D"gmail_quote" st=
yle=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div =
dir=3D"ltr">
Given that the speed at which the block chain advances is kind of unpredict=
able, 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 a=
llow more attempts until it'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"><<a href=3D"javascri=
pt:_e(%7B%7D,'cvml','voisine@gmail.com');" target=3D"_blank=
">voisine@gmail.com</a>></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's based on the block height, not the block'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'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 <<a href=3D"javascript:_e=
(%7B%7D,'cvml','will.yager@gmail.com');" target=3D"_blank">=
will.yager@gmail.com</a>> wrote:<br>
> On Thu, Jul 24, 2014 at 10:39 PM, Gregory Maxwell <<a href=3D"javas=
cript:_e(%7B%7D,'cvml','gmaxwell@gmail.com');" target=3D"_b=
lank">gmaxwell@gmail.com</a>><br>
> wrote:<br>
>><br>
>><br>
>> Is breadwallet tamper resistant & zero on tamper hardware? oth=
erwise<br>
>> this sounds like security theater.... I attach a debugger to the<b=
r>
>> 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 p=
erhaps<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>
</div></div><div><div>> ------------------------------------------------=
------------------------------<br>
> Want fast and easy access to all the code in your enterprise? Index an=
d<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's largest cod=
e<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/bds</a><br>
> _______________________________________________<br>
> Bitcoin-development mailing list<br>
> <a href=3D"javascript:_e(%7B%7D,'cvml','Bitcoin-developmen=
t@lists.sourceforge.net');" target=3D"_blank">Bitcoin-development@lists=
.sourceforge.net</a><br>
> <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>
><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'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 href=3D"javascript:_e(%7B%7D,'cvml','Bitcoin-development@lis=
ts.sourceforge.net');" target=3D"_blank">Bitcoin-development@lists.sour=
ceforge.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>-- <br><br>Aaron Voisine<br><a href=3D"http://breadwal=
let.com" target=3D"_blank">breadwallet.com</a><br>
--e89a8ff242598d5f8304ff05a03b--
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