On Wed, Apr 8, 2015 at 7:50 PM, Stephen Morse <stephencalebmo...@gmail.com> wrote: > Seeking feedback on a proposal that will allow a transaction signer to > explicitly specify what is to be serialized for the signature hash. The > basic idea is to make the nHashType general enough that we won't need a new > sighash flag every time a new use case comes up. > > If implemented into bitcoin (via a soft fork), this would make malleability > almost a non-issue (the TXID referenced by inputs just need to be updated > previous TX changes) and would enable hardware wallets to securely sign > without needing to download/process each transaction it spends from.
I'm not sure if I'm super fond of that particular non-programmatic but many options approach; It sort of has the problem that there are relatively few useful options that don't rapidly extend into a choose your own adventure with too many options to count; so you take a complexity penalty perhaps without a matching functionality payoff. but thats not why I'm commenting... I wonder if anyone noticed that any sighash masking that eliminates the txin txid enables covenants? Covenants are payments which constrain their future payments (like deed covenants), I've written about them in the past https://bitcointalk.org/index.php?topic=278122.0 ... they can sometimes be pretty useful but are also potentially a irritating hit to fungibility, at least if used stupidly. the approach here is that you make the scriptpubkey contain "[push: 0x30, 0x06, 0x02, 0x01, 0x04, 0x02, 0x01, 0x04, flags] [push pubkey resulting from pubkey recovery] OP_CHECKSIG" and set the flags to match only the things you want to enforce in the spending transaction hash them up and recover the EC public point. You can think of that construct as giving a you a OP_MASKED_TRANSACTION_HASH_EQUALS ... the recovered pubkey is just a kind of message hash, though a weird and expensive to compute one. I don't currently see how to get a perpetual covenant out of it-- e.g. a coin that anyone can spend, but only to its same scriptpubkey, (the obvious way requires the ability to be able to checksig stuff on the stack) though I wouldn't be shocked if it were possible with a sufficiently complex sighash flag and nothing else. ------------------------------------------------------------------------------ BPM Camp - Free Virtual Workshop May 6th at 10am PDT/1PM EDT Develop your own process in accordance with the BPMN 2 standard Learn Process modeling best practices with Bonita BPM through live exercises http://www.bonitasoft.com/be-part-of-it/events/bpm-camp-virtual- event?utm_ source=Sourceforge_BPM_Camp_5_6_15&utm_medium=email&utm_campaign=VA_SF _______________________________________________ Bitcoin-development mailing list Bitcoinemail@example.com https://lists.sourceforge.net/lists/listinfo/bitcoin-development