Coldcard signing device integration

[darosior]

Coldcard recently announced experimental Miniscript signing support. This issue is for discussing and tracking the integration of Coldcard with Liana.

[matthiasdebernardini]

From my view, it is the how the api work through https://github.com/alfred-hodler/rust-coldcard library. For my case I was missing a specific flag https://github.com/alfred-hodler/rust-coldcard/pull/9/files

what do you mean from your view? I am using the API right now, it doesn't work how you are describing it (though it would be nice) you have to send it a psbt to sign, if that goes well, then you can ask it for the finalized transaction.

I am not sure which feature flag you are referring to which allows an API to sign and return the transaction in one go, if its there please let me know since I could trim away some code. Thank you.

[pythcoiner]

@scgbckbone, does both mk3/mk4 support miniscript or only mk4? what about limitations?

[scgbckbone]

@scgbckbone, does both mk3/mk4 support miniscript or only mk4? what about limitations?

only Mk4 and only in edge firmware release

miniscript limitations: https://github.com/Coldcard/firmware/blob/edge/docs/miniscript.md#limitations taproot and minitapscript limitations https://github.com/Coldcard/firmware/blob/edge/docs/taproot.md

[scgbckbone]

From my view, it is the how the api work through https://github.com/alfred-hodler/rust-coldcard library. For my case I was missing a specific flag https://github.com/alfred-hodler/rust-coldcard/pull/9/files

what do you mean from your view? I am using the API right now, it doesn't work how you are describing it (though it would be nice) you have to send it a psbt to sign, if that goes well, then you can ask it for the finalized transaction.

I am not sure which feature flag you are referring to which allows an API to sign and return the transaction in one go, if its there please let me know since I could trim away some code. Thank you.

this is misunderstanding and you're right you need 2 steps - what I was describing was cli signing workflow https://github.com/Coldcard/ckcc-protocol/blob/11c711e929a090ec29ccd2a05d094aa3d2cbc113/ckcc/cli.py#L481-L548

[pythcoiner]

rstanding and you're right you need 2 steps - what I was describing was cli signing workflow

is mk3 on roadmap or not planned to support miniscript on it?

[darosior]

@edouardparis mentioned to me this is close to being done. #847 should be testable by anyone with a coldcard soon!

[pythcoiner]

@scgbckbone currently doing a round of test on #847, while verifying address on CC, if i want to Press (4) to view QR Code on the coldcard, it crash:

I had to restart the CC to go back normal

[scgbckbone]

great find @pythcoiner! thank you. Patch here https://github.com/Coldcard/firmware/pull/317

[pythcoiner]

@scgbckbone is it normal that CC follow the normal miniscript flow even if the wallet 'allias' used for registration and the one use on psbt sign does not match, by example using async-hwi cli tool:

• I register descriptor:

  hwi wallet register --name "Liana" --policy <descriptor>

• Then i ask to sign w/ a different wallet name:

  hwi psbt sign --wallet-name "Liana2" --wallet-policy <descriptor> --psbt <psbt>

  and CC let me sign, is it about CC just check if the descriptor is registered but not if wallet_name/aliases match?

[scgbckbone]

There is currently no way to specify target wallet name for signing on CC back-end. It is always chosen automatically trying to match PSBT to some registered wallet.

Looking at async-hwi CC PR it seems to me your name flag is just ignored. Coldcard.sign_tx only takes PSBT as argument.

There is currently no way to specify target wallet name for signing on CC back-end

I'm planning to add this in the next iteration. Can be really useful if you have two policies where only order of keys is different (keys are the same just policy is different). But we do not have (yet) policy or descriptor in PSBT - meaning that our tx to registered wallet matching can fail in those situation.

[pythcoiner]

ok, so it means, we (now) just send psbt and CC just iterate trough the 'wallet' list to check if one matching?

[scgbckbone]

yes

[pythcoiner]

@scgbckbone, does the CC HSM mode functionning w/ miniscript wallets?

[scgbckbone]

@scgbckbone, does the CC HSM mode functionning w/ miniscript wallets?

yes

[edouardparis]

847 is merged, it relies on https://github.com/wizardsardine/async-hwi/ master which relies on this current branch of rust-coldcard https://github.com/alfred-hodler/rust-coldcard/pull/11

We will update later with proper crates versions when crates are published.

Thank you all for contributing !

[kloaec]

Congratulations everyone :) @scgbckbone do you have an ETA for publishing the corresponding firmware publicly? Happy to announce it with you in any way or form.

[scgbckbone]

thanks guys!

We're "almost ready", just need to do the pre-release dance, I hope it'll be out this week... Keep you posted

[scgbckbone]

it is out folks https://coldcard.com/downloads/2024-01-18T1507-v6.2.2X-mk4-coldcard.dfu

[scgbckbone]

I tested liana master - no issues found. UX is very smooth, like it a lot

[kloaec]

Hello @scgbckbone and @edouardparis , finally received a Coldcard Q, i upgraded to 0.0.6Q. After adding the udev, i can get the xpub no problem, but i cannot register the descriptor. It briefly shows "receiving" or something on the screen, but then goes back to the menu and i get an error on Liana. "Decoding(Protocol("Unknown cmd")).

Might be that the Q doesn't have Miniscript support yet? Or do we need to change something in our async-hwi?

[darosior]

i upgraded to 0.0.6Q.

Is this the Edge firmware?

[kloaec]

All versions are Beta for Q, no Edge releases.

[scgbckbone]

We currently do not have edge Q - so no miniscript/tr support in there - soon TM