Hello,

I posted this in Coldcard reddit but didn't really get a proper explanation so I hope someone can explain what is really the issue.

As per the Coldcard guide, you would need to export .json file and open it with Electrum where you would see all your addresses but you need Coldcard to sign a transaction to send coins (either via cable or PTSB signed file). This works with no issues.

However, when I extract zpub master public key and add it to watch only wallet in Electrum, I get exactly the same addresses and balances as with .json file. But when I try to sign a transaction by extracting PTSB file, it doesn't work, Coldcard gives error message that wallet signatures don't match.

Can someone explain the difference between .json file and zpub master key. Do they contain exactly the same data in different format or there is a real difference. Also, is there an increased risk by exposing .json file to the public/hackers vs xpub/zpub?
Someone from Coinkite suggested that the issue is probably different paths, but if the paths are different, wouldn't you get different addresses? In my case, I get 2 identical Electrum wallets with exactly same addresses (native segwit). Except when using zpub in Electrum, I can't sign a transaction (different master key fingerprint).

Thanks in advance.