I hadn't thought of that... There is a solution, I think, but it makes the operation less simple. If a transaction contains at least two OP_TXHASHVERIFY-protected inputs, signed without ANYONECANPAY, their signatures would cover the other input's OP_TXHASHVERIFY hash, right? /Rune On Sat, Sep 17, 2016 at 10:56 PM, Matt Corallo wrote: > (removing the list) > > Because the tx hash in your construction is not signed, someone wishing to > maleate a transaction may do so by also updating the hash in the scriptSig. > > Matt > > On September 17, 2016 4:45:17 PM EDT, "Rune K. Svendsen via bitcoin-dev" < > bitcoin-dev@lists.linuxfoundation.org> wrote: > >> I would really like to be able to create transactions that are immune to >> transaction ID malleability now, so I have been thinking of the simplest >> solution possible, in order to get a BIP through without too much trouble. >> >> An opcode we could call OP_TXHASHVERIFY could be introduced. It would be >> defined to work only if added to a scriptSig as the very first operation, >> and would abort if the hash of the transaction **with all OP_TXHASHVERIFY >> operations (including stack push) removed** does not match what has been >> pushed on the stack. >> >> So, in order to produce a transaction with one or more inputs protected >> against tx ID malleability, one would: >> >> 1. Calculate tx ID of the tx: TX_HASH >> 2. For each input you wish to protect, add "0x32 $TX_HASH >> OP_TXHASHVERIFY" to the beginning of the scriptSig >> >> When evaluating OP_TXHASHVERIFY, we make a copy of the tx in question, >> and remove the "0x32 <32 bytes> OP_TXHASHVERIFY" sequence from the >> beginning of all scriptSigs (if present), and abort if the tx copy hash >> does not match the top stack item. >> >> This is a very simple solution that only adds 34 bytes per input, and >> when something better becomes available (eg. Segwit), we will stop using >> this. But in the meantime it's very valuable to be able to not worry about >> tx ID malleability. >> >> Please let me know what you think. >> >> >> >> /Rune >> >> ------------------------------ >> >> bitcoin-dev mailing list >> bitcoin-dev@lists.linuxfoundation.org >> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev >> >>