Re: [bitcoin-dev] Adding xpub field to PSBT to make multisig more secure

2019-05-09 Thread Dmitry Petukhov via bitcoin-dev
> Therefore, the input==output check is sufficient: if I use the same > set of signers for an input and an output, I can be sure that the > change goes to the same multisig wallet. This is sufficient, in a simple case. I consider cases where spending from different wallets ('wallet

Re: [bitcoin-dev] Adding xpub field to PSBT to make multisig more secure

2019-05-09 Thread jan matejek via bitcoin-dev
hello, On 07. 05. 19 15:40, Dmitry Petukhov via bitcoin-dev wrote: > At the setup phase, hardware wallet can sign a message that consists of > xpubs of participants, and some auxiliary text. It can use the key > derived from the master key, with path chosen specifically for this > purpose. This

Re: [bitcoin-dev] Adding xpub field to PSBT to make multisig more secure

2019-05-07 Thread Dmitry Petukhov via bitcoin-dev
> > Even with this additions to the PSBT format, I think PSBT-signing > > devices still need to store the xpubs of their co-signers. It's not > > possible to safely show an incoming address to the user without a > > full understanding of the other keys in a "multisig wallet". Also, > > it

Re: [bitcoin-dev] Adding xpub field to PSBT to make multisig more secure

2019-05-07 Thread Stepan Snigirev via bitcoin-dev
> I'd rather see the xpubs shared in the global section of the file, > with the restriction that they must/should only include the hardened > prefix of the path. The existing bip32 derivation path included in > individual inputs and outputs be merged in as needed. > After all in a typical PSBT, we

Re: [bitcoin-dev] Adding xpub field to PSBT to make multisig more secure

2019-05-03 Thread Peter D. Gray via bitcoin-dev
On Fri, Apr 26, 2019 at 05:21:06PM +0200, Stepan Snigirev wrote: ... > Currently in PSBT there is no way to reliably say if the output uses the > keys derived from the same root keys as the inputs aside from the key owned Writing the multisig support for Coldcard, I've come to the same

Re: [bitcoin-dev] Adding xpub field to PSBT to make multisig more secure

2019-05-02 Thread Andrew Chow via bitcoin-dev
Hi Stepan, I think that this would be a good extension. Just for clairty, by xpub, do you mean the extended serialization format defined in BIP 32 or the Base58 check encoded string of that serialization? Andrew On 4/26/19 11:21 AM, Stepan Snigirev via bitcoin-dev wrote: > Hi list, > > I was

[bitcoin-dev] Adding xpub field to PSBT to make multisig more secure

2019-04-26 Thread Stepan Snigirev via bitcoin-dev
Hi list, I was looking at the bip174 PSBT specs, in particular for multisignature setup, and I think with current spec there is a way to steal user funds in M of N setup with M ≤ N/2. I made a small write-up on this: https://github.com/stepansnigirev/random_notes/blob/master/psbt_multisig.md To