I’m just going to write, this won’t be polished.
If you have/use a coldcard MK3 without a passphrase, that wasn’t setup with 100+ dice rolls, you need to move your funds out of that coldcard as soon as possible to safe harbor.
If you have/use a coldcard MK4/5/Q without a passphrase, that wasn’t setup with 100+ dice rolls, you need to move your funds out of that coldcard sooner then latter to safe harbor.
If you have/use a coldcard MK3/MK4/5/Q with a passphrase and/or that was setup with 100+ dice rolls, you have more time. It could very well be safe for the long term too, but you’d be wise to migrate to safer harbor eventually.
If you use any of these devices and forget what your setup is, you need to move to safe harbor as soon as possible.
What is safe harbor at this point in time? For MK3’s with no passphrase/no dice – literally anything else. Hot wallets are better in this moment in time (blue wallet, sparrow wallet). Exchanges are also an option. Adding a 16 character passphrase on top of your Mk3 wallet is also an option and helps. Another hardware wallet from a different vendor is better too. Anything else is better at this moment. Your funds are at severe risk in a mk3 here. But none of these safe harbours are long term solutions, they’re short term safety nets for an extreme situation. Consider your safe harbour options carefully and pick the strongest one for your situation.
Safe harbor for the MK4/5/Q’s with no dice/no passphrase is the same situation to be honest. Get it off somewhere else, anywhere else.
Before moving to hot wallets/exchanges please consider if you have other more secure options available. A spare hardware wallet from another vendor, trezor, ledger etc might be better in this moment too.
Ideally for everyone else not in the extreme conditions, migrating away from coldcard eventually is probably wise here for several reasons I won’t get into yet, but are probably obvious. A 2/3 Multisig setup from multiple different hardware wallet brands is ideal long term, and guards against this attack/bug. Seedsigner, Krux, Trezor Model 5 Bitcoin only version, are good options to consider for such a multsig arrangement at this point in time. I don’t believe it wise to reuse coldcards for long term storage even if updated at this point in time. This article (link below) is a good follow up on entropy generation offline with analog methods. This guards against this coldcard attack/bug.
https://btcmaxis.com/article.html?id=7554e7cb-d8aa-45d5-95c8-adea8d87ea23
If you trusted Cold Card to properly use their secure element, how can you be sure they properly used your dice roll entropy? I know you can check the outputs with a CLI script but who actually does that?
I'd go even farther and say just ditch Cold Card altogether. You have nothing to gain by staying and everything to lose.
Best solution.
For completeness:
Review the code, import their sha256(seed) in python and test that
sha256(seed).update(<ascii 1-6>).digest()is deterministic vs, say@noble/hashes. Then do a test run on your cold card and note the displayed digest is the same as openssl says for the same sequence.Take the final outcome from openssl, run it through any bip39 lib, i.e. from the rust crate with the same name. Verify that on a number of derivation paths xpubs, single pubkeys and addresses are the same.
Do all this for testnet and you can also test signing.
yup
Interesting post... I just disagree with putting your funds on an exchange since it's like Russian roulette (don't get involved with any of them) as it's not recommended.
Blockstream wallets are quite secure and are not under attack, as their creators have already announced!
yup, blockstream is a good option here to, main point is that anything right now in the extreme mk3 etc scenarios is better