📅 Original date posted:2016-03-02
📝 Original message:On Wed, Mar 2, 2016 at 5:14 PM, David A. Harding via bitcoin-dev
<bitcoin-dev at lists.linuxfoundation.org> wrote:
> On Wed, Mar 02, 2016 at 02:56:14PM +0000, Luke Dashjr via bitcoin-dev wrote:
>> To alleviate this risk, it seems reasonable to propose a hardfork to the
>> difficulty adjustment algorithm so it can adapt quicker to such a significant
>> drop in mining rate.
>
> Having a well-reviewed hard fork patch for rapid difficulty adjustment
> would seem to be a useful reserve for all sorts of possible problems.
> That said, couldn't this specific potential situation be dealt with by a
> relatively simple soft fork?
[...]
What you are proposing makes sense only if it was believed that a very
large difficulty drop would be very likely.
This appears to be almost certainly untrue-- consider-- look how long
ago since hashrate was 50% of what it is now, or 25% of what it is
now-- this is strong evidence that supermajority of the hashrate is
equipment with state of the art power efficiency. (I've also heard
more directly-- but I think the this evidence is more compelling
because it can't be tainted by boasting). If a pre-programmed ramp and
drop is set then it has the risk of massively under-setting
difficulty; which is also strongly undesirable (e.g. advanced
inflation and exacerbating existing unintentional selfish mining)...
and that is before suggesting that miners voluntarily take a loss of
inflation now.
So while I think this concern is generally implausible; I think it's
prudent to have a difficulty step patch (e.g. a one time single point
where a particular block is required to lower bits a set amount) ready
to go in the unlikely case the network is stalled. Of course, if the
alternative is "stuck" from a large hashrate drop the deployment would
be both safe and relatively uncontroversial. I think the
unfavorability of that approach is well matched to the implausibility
of the situation, and likely the right coarse of action compared to
risky interventions that would likely cause harm. The cost of
developing and testing such a patch is low, and justified purely on
the basis of increasing confidence that an issue would be handled (a
fact _I_ am perfectly confident in; but apparently some are not).
With respect what Luke was suggesting; without specifics its hard to
comment, but most altcoin "tolerate difficulty drop" changes have made
them much more vulnerable to partitioning attacks and other issues
(e.g. strategic behavior by miners to increase inflation), and have
actually been exploited in practice several times (solidcoin's being
the oldest I'm aware of). Many survived a fairly long time before
being shown to be pretty broken, simply because they were deployed in
cases where no one cared to attack. I'm currently doubtful that
particular path would be fruitful.
Gregory Maxwell [ARCHIVE] /
npub1f2…crwet
2023-06-07 17:49:35
in reply to nevent1q…cd5g
Author Public Key
npub1f2nvlx49er5c7sqa43src6ssyp6snd4qwvtkwm5avc2l84cs84esecrwetPublished at
2023-06-07 17:49:35Event JSON
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"content": "📅 Original date posted:2016-03-02\n📝 Original message:On Wed, Mar 2, 2016 at 5:14 PM, David A. Harding via bitcoin-dev\n\u003cbitcoin-dev at lists.linuxfoundation.org\u003e wrote:\n\u003e On Wed, Mar 02, 2016 at 02:56:14PM +0000, Luke Dashjr via bitcoin-dev wrote:\n\u003e\u003e To alleviate this risk, it seems reasonable to propose a hardfork to the\n\u003e\u003e difficulty adjustment algorithm so it can adapt quicker to such a significant\n\u003e\u003e drop in mining rate.\n\u003e\n\u003e Having a well-reviewed hard fork patch for rapid difficulty adjustment\n\u003e would seem to be a useful reserve for all sorts of possible problems.\n\u003e That said, couldn't this specific potential situation be dealt with by a\n\u003e relatively simple soft fork?\n[...]\n\n\nWhat you are proposing makes sense only if it was believed that a very\nlarge difficulty drop would be very likely.\n\nThis appears to be almost certainly untrue-- consider-- look how long\nago since hashrate was 50% of what it is now, or 25% of what it is\nnow-- this is strong evidence that supermajority of the hashrate is\nequipment with state of the art power efficiency. (I've also heard\nmore directly-- but I think the this evidence is more compelling\nbecause it can't be tainted by boasting). If a pre-programmed ramp and\ndrop is set then it has the risk of massively under-setting\ndifficulty; which is also strongly undesirable (e.g. advanced\ninflation and exacerbating existing unintentional selfish mining)...\nand that is before suggesting that miners voluntarily take a loss of\ninflation now.\n\nSo while I think this concern is generally implausible; I think it's\nprudent to have a difficulty step patch (e.g. a one time single point\nwhere a particular block is required to lower bits a set amount) ready\nto go in the unlikely case the network is stalled. Of course, if the\nalternative is \"stuck\" from a large hashrate drop the deployment would\nbe both safe and relatively uncontroversial. I think the\nunfavorability of that approach is well matched to the implausibility\nof the situation, and likely the right coarse of action compared to\nrisky interventions that would likely cause harm. The cost of\ndeveloping and testing such a patch is low, and justified purely on\nthe basis of increasing confidence that an issue would be handled (a\nfact _I_ am perfectly confident in; but apparently some are not).\n\nWith respect what Luke was suggesting; without specifics its hard to\ncomment, but most altcoin \"tolerate difficulty drop\" changes have made\nthem much more vulnerable to partitioning attacks and other issues\n(e.g. strategic behavior by miners to increase inflation), and have\nactually been exploited in practice several times (solidcoin's being\nthe oldest I'm aware of). Many survived a fairly long time before\nbeing shown to be pretty broken, simply because they were deployed in\ncases where no one cared to attack. I'm currently doubtful that\nparticular path would be fruitful.",
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