OP_CHECKDATASIG
A Bitcoin Cash opcode, enabled in November 2018, that checks a signature over arbitrary data; it enabled oracles and early covenants and was one cause of the BSV split.
The wiki's angle: one opcode was enough for BSV supporters to call ABC's 2018 roadmap a redesign, and years later BCH developers credited the same opcode with making covenants possible.[6][5]
Specification
The specification says OP_CHECKDATASIG and OP_CHECKDATASIGVERIFY “check whether a signature is valid with respect to a message and a public key”[1]. It adds that OP_CHECKDATASIG “permits data to be imported into a script, and have its validity checked against some signing authority such as an "Oracle"”[1]. The opcodes were enabled in the 15 November 2018 Bitcoin Cash upgrade with CTOR[2].
On the show
Vlad asked Amaury Séchet about “the Magnetic Anomaly hard fork with OP_CHECKDATASIG and CTOR”[3]. Séchet called the opcode “a big enabler” for scripts[4]. Rosco Kalis said that before later upgrades “the only thing that kind of was there that really did enable interesting smart contracts on BCH was CheckDataSig”, which allowed covenants[5]. nChain's objection is covered in Bitcoin SV[6].
References
- primaryBitcoin Cash, OP_CHECKDATASIG and OP_CHECKDATASIGVERIFY specification [archived]
- primaryBitcoin Cash, “2018 November 15 Network Upgrade Specification” (activation 1542300000) [archived]
- episodeS17 E19: Vlad on the November 2018 Magnetic Anomaly fork▶ listen at 1:49:21timestamp transcript-derived, pending a listen [archived]
- episodeS17 E19: Amaury Séchet explains OP_CHECKDATASIG and CTOR▶ listen at 1:49:37timestamp transcript-derived, pending a listen [archived]
- episodeS17 E26: Rosco Kalis on CheckDataSig covenants▶ listen at 5:50:31timestamp transcript-derived, pending a listen [archived]
- btkBitcoin SV: Big Blocks All the Way (BTCTKVR: Forks!) [archived]