Hi all, This is an alternative to jl2012's BIPZZZ (OP_PUSHTXDATA[1]). It riffs on the (ab)use of OP_CHECKSIGFROMSTACK that Russell[2] used to implement covenants[3]. I've been talking about it to random people for a while, but haven't taken time to write it up.
The idea is to provide a OP_TXMERKLEVERIFY that compares the top stack element against a merkle tree of the current tx constructed like so[4]: TXMERKLE = merkle(nVersion | nLockTime | fee, inputs & outputs) inputs & outputs = merkle(inputmerkle, outputmerkle) input = merkle(prevoutpoint, nSequence | inputAmount) output = merkle(nValue, scriptPubkey) Many variants are possible, but if we have OP_CAT, this makes it fairly easy to test a particular tx property. A dedicated OP_MERKLE would make it even easier, of course. If we one day HF and add merklized TXIDs[5], we could also use this method to inspect the tx *being spent* (which was what I was originally trying to do). Thanks for reading! Rusty. [1] https://github.com/jl2012/bips/blob/vault/bip-0ZZZ.mediawiki [2] Aka Dr. "Not Rusty" O'Connor. Of course both of us in the same thread will probably break the internet. [3] https://blockstream.com/2016/11/02/covenants-in-elements-alpha.html [4] You could put every element in a leaf, but that's less compact to use: cheaper to supply the missing parts with OP_CAT than add another level. [5] Eg. use the high nVersion bit to say "make my txid a merkle". _______________________________________________ bitcoin-dev mailing list bitcoin-dev@lists.linuxfoundation.org https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev