From tadge at lightning.network Thu Nov 19 19:21:12 2015 From: tadge at lightning.network (Tadge Dryja) Date: Thu, 19 Nov 2015 11:21:12 -0800 Subject: [Lightning-dev] Lightning, the death of BIP62, and Segregated Witness In-Reply-To: References: <87si42n1ir.fsf@rustcorp.com.au> <1447920788.2353.12.camel@ultimatestunts.nl> Message-ID: With sighash_noinput, signers don't include their input's txid and index. An even more powerful version would not even sign the pubkeyscript of the input, which would allow some cool constructions. In the case that there are multiple utxo outpoints which would be satisfied by a single signature, miners can decide. It can be dangerous for this reason if you re-use pubkeys. So don't! Especially in a multisig setting, it seems unlikely to be a problem. -Tadge On Thu, Nov 19, 2015 at 11:15 AM, zaki at manian.org wrote: > sighhash_noinput is the miner chooses which which utxo is consumed > assuming there are multiple candidates variant of the idea? > > > > On Thu, Nov 19, 2015 at 11:12 AM, Tadge Dryja > wrote: > >> I've joked that BIP62 is the "whack-a-mole" BIP in that it addresses many >> vectors for txid malleability, but maybe there are more. And more >> importantly, it addresses 3rd party malleability. It's not helpful in the >> context of lightning channel creation because ECDSA sigs are inherently >> malleable. You can always re-sign the same message with a different >> k-value and get a different signature. >> >> The functionality that's needed is to be able to reliably spend from >> unconfirmed transactions. Segregated witness can accomplish that, but it >> quite a large hard-fork change. sighash_noinput can also accomplish that: >> as input txids are not signed, if they change, the spending transaction can >> be modified while leaving counterparty signatures intact. >> >> I'm hoping to start a new "testnet-L" similar to testnet3, with this >> sighash type so that we can test malleability mitigation out. >> >> (Oh also, hi mailing list, sorry I have not posted till now! But I will >> start posting!) >> >> -Tadge >> >> On Thu, Nov 19, 2015 at 9:56 AM, Mark Friedenbach >> wrote: >> >>> The basic idea of the soft-fork plan is very simple --- have the >>> scriptPubKey be just the 20-byte hash of the redeem script. The scriptSig >>> of the spending input is empty. The actual scriptSig, with the redeem >>> script and signatures, is contained in a separate Merkle tree committed to >>> elsewhere in the block (e.g. in the last output of the coinbase, or the >>> last output of the last transaction). >>> >>> On Thu, Nov 19, 2015 at 7:31 AM, Greg Sanders >>> wrote: >>> >>>> The hardfork variant is quite simple, if I understood it correctly. You >>>> just stick the signatures in another parallel merkle tree. So if you don't >>>> want to validate signatures, just don't download them, and validate >>>> everything else. TXIDs don't use the signature at all. Nothing to malleate, >>>> AFAIK. Not sure what the softfork plan is, but it will be a talk at Scaling >>>> Bitcoin HK. >>>> >>>> On Thu, Nov 19, 2015 at 10:28 AM, Glenn Tarbox, PhD >>>> wrote: >>>> >>>>> >>>>> On Thu, Nov 19, 2015 at 4:33 AM, sickpig at gmail.com >>>>> wrote: >>>>> >>>>>> Hi Pierre >>>>>> >>>>>> you could start here >>>>>> >>>>>> >>>>>> https://github.com/ElementsProject/elementsproject.github.io#segregated-witness >>>>>> >>>>>> https://people.xiph.org/~greg/blockstream.gmaxwell.elements.talk.060815.pdf >>>>>> https://github.com/ElementsProject/elements >>>>> >>>>> >>>>> There was a brief blip on Reddit: >>>>> >>>>> >>>>> https://www.reddit.com/r/Bitcoin/comments/3ngtx5/could_the_segregated_witness_part_of_the/cwnthlh >>>>> >>>>> Its weird how little information there is on Segregated Witness. I'm >>>>> guessing its a simple concept and those working on it (sipa / gmaxwell) >>>>> haven't felt the need to write it up. >>>>> >>>>> That it "apparently" can be done with a soft fork similar to P2SH is >>>>> good news... I guess... >>>>> >>>>> >>>>> -- >>>>> Glenn H. Tarbox, PhD >>>>> =]|[= >>>>> >>>>> _______________________________________________ >>>>> Lightning-dev mailing list >>>>> Lightning-dev at lists.linuxfoundation.org >>>>> https://lists.linuxfoundation.org/mailman/listinfo/lightning-dev >>>>> >>>>> >>>> >>>> _______________________________________________ >>>> Lightning-dev mailing list >>>> Lightning-dev at lists.linuxfoundation.org >>>> https://lists.linuxfoundation.org/mailman/listinfo/lightning-dev >>>> >>>> >>> >>> _______________________________________________ >>> Lightning-dev mailing list >>> Lightning-dev at lists.linuxfoundation.org >>> https://lists.linuxfoundation.org/mailman/listinfo/lightning-dev >>> >>> >> >> _______________________________________________ >> Lightning-dev mailing list >> Lightning-dev at lists.linuxfoundation.org >> https://lists.linuxfoundation.org/mailman/listinfo/lightning-dev >> >> > -------------- next part -------------- An HTML attachment was scrubbed... URL: