Published on: 2018-08-30T20:55:17+00:00
Bitcoin's non-overlapping difficulty calculation has been known to be vulnerable to gaming with inaccurate timestamps since 2012. This vulnerability can be fixed with a soft-fork that further constrains block timestamps, and several proposals have been suggested. One proposal being discussed is to require the timestamp of block (2016x) not smaller than its parent block by t-seconds, with 0 ≤ t ≤ infinity. Reducing the value of t is a softfork. The aim is to find a t which is small-enough-to-prohibit-time-wrap-attack but also big-enough-to-avoid-split.A chain-split would happen even without any attack if a naive fix is adopted, which requires every block (2016x) to have a timestamp not smaller than that of its parent block. This fix involves mandatory upgrade of pool software and will cause a chain split unless super-majority of miners are enforcing the new rules. The best way is to do it with something like BIP34, which also requires new pool software.Gregory Maxwell, a Bitcoin Core developer, posted on the bitcoin-dev mailing list about this issue in August 2018. He explained that the vulnerability had been known since 2012 and could be exploited to increase the rate of block production beyond the system's intentional design. Several proposals for fixing this vulnerability with a soft-fork have been suggested, but none are backwards compatible. Maxwell had put a demonstration of timewarp early in the testnet3 chain to allow people to test mitigations against it.Despite the vulnerability, there hasn't been a big priority into fixing it because it requires a majority hashrate and could easily be blocked if someone started using it. However, several proposals have been suggested that are fully compatible with existing behavior and only trigger in exceptional circumstances like a timewarp attack. Therefore, the risk of deploying these mitigations would be minimal.In light of this, Maxwell suggested asking the list if anyone else is aware of a favorite backwards compatible timewarp fix proposal they want to point out before dusting off his old fix and perhaps prematurely causing fixation on a particular approach.
Updated on: 2023-08-01T23:44:30.335308+00:00