multi signature – Is this scheme for multisig audit of Trezor + Coldcard ok?

My plan is to make a multisig between coldcard and trezor. I want to audit and verify that I indeed own the 2 keys of these wallets, using a raspberry pi zero (no wifi/bluetooth by definition) on a very old HDMI tv with no internet either, and using a virtual keyboard and simply a mouse on the pi zero.

These are the possible risks I want to mitigate:

To eliminate the risk of the trezor generating a private key I don’t own, I’m gonna put its key on the raspberry pi zero and see that it generates the same master pubkey and shown in trezor. This proves I own this key, but it might be a kew that someone already owns. No problem, that’s why I’m doing multisig.

On the coldcard, I’ll generate a seed using dices, and then verify on the raspberry pi that those dice rolls indeed generate the private key shown by coldcard. This proves that I own a private key that no one owns, because it was generated using dices.

Now that I have 2 private keys that I own, and at least one of them I’m the only owner, I can create a multisig wallet on Ethereum or maybe BlueWallet. I’ll annotate the first 10 addresses generated by the software wallet, and verify if they match on the coldcard and on the trezor. If the 3 show the same 10 set of addresses, I can consider these addresses safe for receiving Bitcoin.

I’ll then receive some Bitcoin on one address, erase both wallets, restore them with the private keys, and then try to spend this Bitcoin, just to make sure I really owned the coins.

What are the possible problems I can encounter? Am I forgetting something important?

PS: I know that if the trezor has a malicious random number generator and it creates a private key that not only myself own, this is a privacy leak, but not a problem. And it’s a privacy leak only when I spend from this address, revealing the public key on the blockchain.

I also plan to use just PBST air-gapped transactions on Coldcard, and a trusted computer to broadcast.

What does bitcoin.org mean when they say about Coldcard Wallet “the final software was not built deterministically like Bitcoin Core”?

I am looking at hardware wallets to store my Bitcoins, and Coldcard Wallet Mk3 seems like a great option. However, at looking at info about it at bitcoin.org, it says that the software is not built deterministically like the consensus Bitcoin Core protocol.

I just want to know if this is true, or the info is outdated. Because in the Coldcards page, I have not found such thing.

Coldcard even claims extreme compatibility with clients such as Bitcoin Core, Electrum of Wasabi Wallet. And it seems to be easy to use it only trough ones personal Full Node.

The other option as a Hardware Wallet I am looking for, is BitBox02.

Thank you in advance,

Ander

My first bitcoin transaction with core and coldcard

I use coldcard and bitcoin core 0.20.1. I have checked how to do it with HWI at https://github.com/bitcoin-core/HWI/blob/master/docs/bitcoin-core-usage.md.
It appears more complex than needed.
With the core’s GUI, I can create a PSBT, save it, and then sign it with an SD card and coldcard. The latter will create a TXN file with the finalized transaction, that I can just broadcast with core.
No need for HWI and only 1 console command (sendrawtransaction) needed.
I am afraid: am I missing something?
Thank you for any suggestion.

My first bitcoin transaction wit core and coldcard

I use coldcard and bitcoin core 0.20.1. I have checked how to do it with HWI at https://github.com/bitcoin-core/HWI/blob/master/docs/bitcoin-core-usage.md.
It appears more complex than needed.
With core’s GUI, I can create a PSBT, save it, and then sign it with an SD card and coldcard. The latter will create a TXN file with the finalized transaction, that I can just broadcast with core.
No need for HWI and only 1 console command (sendrawtransaction) needed.
I am afraid: am I missing something?
Thank you for any suggestion.

multi signature – Can I use coldcard wallet to multisig between it and another wallet?

I want to use coldcard wallet + another device, possibly a smartphone, for multisignature. Ideally I’d like to use Coldcard + Bitpay.

I’ve found tutorials on coldcard multisig: https://www.youtube.com/watch?v=OMpZ5heLsRg but it involves multisig between coldcards only.

I think BitPay is very user friendly so it wouldn’t let you use multisig from importing the pubkey of the coldcard.

What are my options?

hardware wallet – What is the difference between PSBT support in Coldcard and Trezor?

The 10x Security Bitcoin Guide says that the only two hardware wallets support BIP174 (partially signed Bitcoin transactions, or PSBT). However, this Reddit thread says that “You can use PSBT with Trezor via HWI”. This Github issue elaborates.

What is the difference between the level of support of PSBT between Coldcard / Cobo and Trezor? Should a user care?