[bitcoin-dev] Chain width expansion

[Braydon Fuller]

On 10/12/19 1:46 PM, Tier Nolan via bitcoin-dev wrote:

> On Sat, Oct 12, 2019 at 6:56 PM Joachim Strömbergson <joachimstr at protonmail.com> wrote:
>> On different note, one of the problems that I haven't seen mentioned here
>> yet is the timewarp attack. It is relevant to some of the proposed
>> solutions. It should be possible, IIRC, for a malicious node to generate
>> much longer chain with superslow timestamp increase (~5 blocks in 1 second)
>> without increasing difficulty (i.e. staying at min. diff.). This could
>> produce chain that is ~2500 times longer than main chain without having
>> multiple branches.
>>
> [..]
>
> The timewarp bug can be fixed by a basic soft fork.  You just need to limit
> the maximum difference between the timestamp for the first header in a
> period and the last header in the previous period.

Yeah, that makes sense as it corrects the off-by-one error. I think this
solution has been included in a draft proposal "The Great Consensus
Cleanup". It would need to be effective for not only the main chain but
also for any future forked chain.