Median time-past as endpoint for lock-time calculations

en · official · sha256:d1ca9987b1c7d12b2e6778a8d1d424892071264daa441f715cd87c62bffc3fa3

The values for transaction locktime remain unchanged. The difference is only in the calculation determining whether a transaction can be included. Instead of an unreliable timestamp, the following function is used to determine the current block time for the purpose of checking lock-time constraints: enum { nMedianTimeSpan=11 }; int64_t GetMedianTimePast(const CBlockIndex* pindex) { int64_t pmedian[nMedianTimeSpan]; int64_t* pbegin = &pmedian[nMedianTimeSpan]; int64_t* pend = &pmedian[nMedianTimeSpan]; for (int i = 0; i < nMedianTimeSpan && pindex; i++, pindex = pindex->pprev) *(--pbegin) = pindex->GetBlockTime(); std::sort(pbegin, pend); return pbegin[(pend - pbegin)/2]; } Lock-time constraints are checked by the consensus method IsFinalTx(). This method takes the block time as one parameter. This BIP proposes that after activation calls to IsFinalTx() within consensus code use the return value of `GetMedianTimePast(pindexPrev)` instead. The new rule applies to all transactions, including the coinbase transaction.

Referencing norms: TimeLocktimeUsesPreviousMtp, nlocktime_median_time, previous_block_median_time_for_tx, timestamp_strictly_after_median_of_11_predecessors