[Bitcoin-development] Time

Aaron Voisine voisine at gmail.com
Fri Jul 25 02:35:46 UTC 2014

The upcoming release of breadwallet uses the height of the blockchain to
enforce timed pin code lockouts for preventing an attacker from
quickly making multiple pin guesses. This prevents them changing the
devices system time to get around the lockout period.


On Thursday, July 24, 2014, Ron OHara <ron.ohara54 at gmail.com> wrote:

> Hash: SHA1
> I thought I should shortcut my research by asking a direct question here.
> As I understand it, the blockchain actually provides an extra piece of
> reliable data that is not being exploited by applications.
> Which data?  The time.   In this case 'the time' as agreed by >50% of
> the participants, where those participants have a strong financial
> incentive to keep that 'time' fairly accurate. (+/- about 10 minutes)
> Is this a reasonable understanding of 'time'? ... aka timestamps on the
> block
> Ok... 'time' on the blockchain could be 'gamed' ... but with great
> difficulty. An application presented with a fake blockchain can use
> quite a few heuristics to test the 'validity' of the block chain.
> It can review the usual cryptographic proofs, and check that difficulty
> is growing/declining only in a realistic manner up to the most recent
> block. Even use some arbitrary test like difficulty > 10,000,000,000
> ... on the presumption that any less means that the Bitcoin system has
> failed massively from where it currently is and has become an unreliable
> time source.
> Reliable 'time' has been impossible up until now - because you need to
> trust the time source, and that can always be faked.  Using the
> blockchain as an approximate time source gives you a world wide
> consensus without direct trust of any player.
> So if this presumption is correct, then we can now build time capsule
> applications that can not be tricked into exposing their contents too
> early by running them in a virtual environment with the wrong system time.
> Is this right? or did miss I something fundamental?
> Ron
> - --
> public identify: https://www.onename.io/ron_ohara
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> =T5fw
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Aaron Voisine
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