Instead of trying to remove the possibility of transaction malleability, would it make sense to define a new, "canonical transaction hash/ID" (cTxID), which would be a hash of the part of the transaction data which we know is not malleable, and have clients use this cTxID internally, thus making the traditional transaction hash irrelevant for a client to function correctly?
We already have a non-malleable transaction hash: the hash that is signed, ie. the transaction with each scriptSig replaced by the scriptPubKey it redeems. This could be the cTxID. Or is this simply a too fundamental change to the way bitcoin-qt (and all other clients) work in order to be feasible? As far as I can see, it completely solves the issue of not having a canonical ID for a transaction, but it also increases the computational requirements for a node. For one, as far as I can see, it requires the node to index all transactions, because in order to calculate a cTxID, it would be necessary to fetch all transactions referred to by the transaction in question, in order to pull in the scriptPubKeys that are redeemed. On Mon, Feb 10, 2014 at 4:00 AM, Peter Todd <p...@petertodd.org> wrote: > On Mon, Feb 10, 2014 at 12:33:02AM +0100, Pieter Wuille wrote: >> Hello all, >> >> it was something I planned to do since a long time, but with the >> recent related issues popping up, I finally got around to writing a >> BIP about how we can get rid of transaction malleability over time. >> >> The proposed document is here: https://gist.github.com/sipa/8907691 >> >> I expect most rules to not be controversial. Maybe rules 1 and 3, as >> they require modifications to wallet software (Bitcoin Core 0.9 and >> BitcoinJ already implement it, though) and potentially invalidate some >> script functionality. However, these new rules remain optional and >> controlled by an nVersion increase. >> >> Comments please! > > You should probably add making CHECKMULTISIG require the dummy value to > be exactly equal to OP_FALSE; verifying that in the transaction itself is > laborious. A more subtle example is we may want both CHECKSIG and > CHECKMULTISIG to fail the transaction if the signature is invalid but > not exactly equal to OP_FALSE; some transaction forms are significantly > more compact if you can have failed signatures, but that's a source of > malleability. (are there counter examples people can think of?) > > > But as I said on IRC, I'm a bit hesitant to bake in assumptions about > malleability when we have no solid idea if ECC signatures are or are not > malleable on a fundemental level; if "whack-a-mole" anti-malleability is > all we've got it could be ugly if a break is found. Similarly, we may > find we missed something, or some needed change makes the malleability > rules difficult to work with for some new script type that is required. > > I'd rather see a new CHECKSIG mode for the case where malleability > absolutely must be eliminated - certain multi-party protocols - and fix > wallet software instead. (the malleability problems people see are > closely related to inability to handle double-spends and reorgs) But I > can easily see that being an impossible goal engineering wise... > > -- > 'peter'[:-1]@petertodd.org > 0000000000000001465bc2730ffed7493d166d18d288f6cf15e8cdb5d4a3c7b1 > > ------------------------------------------------------------------------------ > Managing the Performance of Cloud-Based Applications > Take advantage of what the Cloud has to offer - Avoid Common Pitfalls. > Read the Whitepaper. > http://pubads.g.doubleclick.net/gampad/clk?id=121051231&iu=/4140/ostg.clktrk > _______________________________________________ > Bitcoin-development mailing list > Bitcoin-development@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/bitcoin-development > ------------------------------------------------------------------------------ Android apps run on BlackBerry 10 Introducing the new BlackBerry 10.2.1 Runtime for Android apps. Now with support for Jelly Bean, Bluetooth, Mapview and more. Get your Android app in front of a whole new audience. Start now. http://pubads.g.doubleclick.net/gampad/clk?id=124407151&iu=/4140/ostg.clktrk _______________________________________________ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development
