[Bitcoin-development] Bitcoin difficulty sanity check suggestion

Matt Corallo bitcoin-list at bluematt.me
Tue Dec 24 08:34:53 UTC 2013

An attacker with some small hashpower isolates you (as an individual)
from the network by MITMing your network. You just switch the the
attackers chain as if nothing happened because of the network rule
that defines it as OK. Today, you will see that you're behind and warn
the user.

Was it really so hard to write a three-sentence paragraph to clarify
the attack instead of insulting people? Still, posting ideas here
without spending time to ensure you understand the Bitcoin network
well is frowned upon.


On 12/23/13 17:51, Ryan Carboni wrote:
> I think you misunderstood my statement. If time > 3 days, and after
> 4 blocks have been mined, then difficulty would be reset.
> In theory, one would have to isolate roughly one percent of the
> Bitcoin network's hashing power to do so. Which would indicate an
> attack by a state actor as opposed to anything else. Arguably, the
> safest way to run Bitcoin is through a proprietary dial-up
> network.
> On Sun, Dec 22, 2013 at 7:22 PM, Mark Friedenbach
> <mark at monetize.io <mailto:mark at monetize.io>> wrote:
> Ryan, these sort of adjustments introduce security risks. If you
> were isolated from the main chain by a low-hashpower attacker, how
> would you know? They'd need just three days without you noticing
> that network block generation has stalled - maybe they wait for a
> long weekend - then after that the block rate is normal but
> completely controlled by the attacker (and isolated from mainnet).
> There are fast acting alternative difficulty adjustment algorithms 
> being explored by some alts, such as the 9-block interval,
> 144-block window, Parks-McClellan FIR filter used by Freicoin to
> recover from just such a mining bubble. If it were to happen to
> bitcoin, there would be sophisticated alternative to turn to, and
> enough time to make the change.
> On 12/22/2013 07:10 PM, Ryan Carboni wrote:
>> I think Bitcoin should have a sanity check: after three days if 
>> only four blocks have been mined, difficulty should be adjusted 
>> downwards.
>> This might become important in the near future. I project a 
>> Bitcoin mining bubble.
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