TransactionBuilder.merge and signature ordering

[dcousens]

I want to see #244 (comment) resolved by 2.0.0 to avoid rabbit holes like #318

[9876691]

Hi,

Do you have a solution for this already as I have an app that does out of order async multi sig signing using javascript.

Algorithm goes something like

1. Collect existing sigs into an array.
2. Sign the input using the new private key and add to above array
3. Get the public keys from the redeem script

            var pubkeyList = this.scriptListPubkey(redeemScript);
            var sigsList = this.scriptListSigs(o.script);
            sigsList.push(Bitcoin.convert.bytesToHex(signature));
            for(x in pubkeyList) {
                    for(y in sigsList) {
                        if(Bitcoin.ecdsa.verify(sighash, 
                Bitcoin.convert.hexToBytes(sigsList[y]), 
                Bitcoin.convert.hexToBytes(pubkeyList[x]))) {
                            s.writeBytes(Bitcoin.convert.hexToBytes(sigsList[y]));
                        }
                    }
                }

Although the above algorithm is slower than having the keys in the correct order, I believe this should be the default.

The point of multi sig is that we don't always have all the keys in the right order. With this algorithm we don't burden the user with collecting sigs and ordering.

[dcousens]

The algorithm is as simple as you say, I just haven't got around to that
yet.
The most help would be building up test cases as that takes the longest
time.

I'd greatly appreciate any contributions toward this :).
On Dec 11, 2014 8:35 PM, "Ian Purton" notifications@github.com wrote:

Hi,

Do you have a solution for this already as I have an app that does out of
order async multi sig signing using javascript.

Algorithm goes something like

1. Collect existing sigs into an array.
2. Sign the input using the new private key and add to above array
3. Get the public keys from the redeem script
4. For each public key For each signature If the signature verifies
   against the public key add it back into the script sig

Although the above algorithm is slower than having the keys in the correct
order, I believe this should be the default.

The point of multi sig is that we don't always have all the keys in the
right order. With this algorithm we don't burden the user with collecting
sigs and ordering.

I can supply code for above if required.

—
Reply to this email directly or view it on GitHub
#320 (comment)
.

[9876691]

Sure, I can help with test cases, coding. What is the best way for us to coordinate ?

[dcousens]

@ianpurton I use IRC and am on the #bitcoinjs-dev channel on Freenode 24/7; so if you leave me a message there I'll always get back to it. We can sync up any times for dev through that as well.

[dcousens]

@ianpurton missed responding to you.

< ianpurton> Regarding issue 320 (Signature ordering.) I think there may be a simple fix for this. In transaction builder sign I could add a sort_sigs parameter to the method. Then if set to true I sort the sigs based on the public keys in the redeem script.

This approach doesn't change any of the necessary implementation needed for Transaction.merge, nor does it help users who will want to do asynchronous signing in a non serial way.

[dcousens]

It also encourages the use of that quasi standard, which IMHO is a quite arbitrary.

[9876691]

Not sure I understand. I'm not proposing that users sort their keys. I'm proposing that I sort the signatures into the correct order ?

I couldn't find a Transaction.merge method.

Basically at the moment if you sign a P2SH transaction BitcoinJS puts the sig at the end of the list of signatures, I'm proposing to place it in it's correct position.

For example if the redeem script has 2 public keys. And the second one gets signed first.

I will sign the first, but put the sig into the beginning of the list of signatures.

Hope this helps.

[dcousens]

Oh, absolutely lets get that functionality in. I don't think that should even be a parameter, but simply the default.
If users want to do something else, they always have Transaction to play with.

[dcousens]

Any pull requests push to https://github.com/bitcoinjs/bitcoinjs-lib/tree/txbmerge

[dcousens]

I think for now lets play with possible solutions, and if it looks like the performance hit of the extra public key verification is a kicker, we'll see what we can do.

[9876691]

@dcousens

Started to look at adding some tests. First test https://github.com/ianpurton/bitcoinjs-lib/commit/ea92aeaf4ea2b6c0c892fdc9b968cbb9c1e98713

Fails, it doesn't get parsed, probably due to the fact it has no signatures yet. Seems ok on http://coinb.in/multisig/