CTOR (canonical transaction ordering)
Bitcoin Cash's November 2018 rule that transactions in a block, after the coinbase, be sorted by txid — one of the two changes behind the BCH/BSV split.
The wiki's angle: a block-ordering rule that most users would never see split Bitcoin Cash in two, because one side saw it as scaling and the other as an unauthorised redesign.[2][3]
Contents
Rule
The Bitcoin Cash specification for the 15 November 2018 upgrade activates when the median time past of the last 11 blocks reaches UNIX time 1542300000[1]. It says that, “With the exception of the coinbase transaction, transactions within a block MUST be sorted in numerically ascending order of the transaction id”[1]. The same upgrade enabled OP_CHECKDATASIG, a 100-byte minimum transaction size, and push-only and clean-stack rules[1].
Dispute
The Takeover BSV feature says CTOR and OP_CHECKDATASIG were “two changes that nobody outside the ABC team had asked for”; ABC said CTOR would enable faster block propagation, while nChain called it an unauthorised redesign and announced Bitcoin SV to reject both[2]. On the show Amaury Séchet called CTOR “like a scalability technology”[3]. The split that followed is covered in the hash war[2].
References
- primaryBitcoin Cash, “2018 November 15 Network Upgrade Specification” (activation 1542300000) [archived]
- btkBitcoin SV: Big Blocks All the Way (BTCTKVR: Forks!) [archived]
- episodeS17 E19: Amaury Séchet explains OP_CHECKDATASIG and CTOR▶ listen at 1:49:37timestamp transcript-derived, pending a listen [archived]