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building @ block

FROST certainly has potential to reduce L1 transaction costs and add flexibility and privacy in a system like Bitkey. Right this moment we’re focused on a few other things though, you can see more about our roadmap here: https://bitkey.build/building-better-bitcoin-self-custody/

Nah, I just mostly use socials for representing what I’m building for people and engaging on that. The rest of the time I’m reading and listening and learning here

You can always move your bitcoin without Block using the two keys you hold, even if Block servers are unreachable. And if you can’t get the Bitkey app from the app stores anymore, you can move your bitcoin using Bitkey’s Emergency Access Kit (https://support.bitkey.world/hc/en-us/articles/24395170222868-What-is-an-Emergency-Access-Kit-and-how-does-it-work) using your hardware and cloud backup. Are there other scenarios you’re looking to use seed phrases for?

Right here on nostr works just fine. What do you have in mind?

You can consolidate, but not yet manage UTXOs directly in Bitkey. Could you tell me more about how you want to manage UTXOs? Individual UTXO choice per transaction, or more like two separate accounts, something else?

The inheritance plan relies on the Block/Bitkey server to fulfill claims. If we were to go out of business, we'd aim to give 6 months' notice so customers can sweep their bitcoin. After that, they’d need new arrangements to manage inheritance. If you’re using Bitkey and see us go out of business, you could move your funds to another wallet.

If you're concerned about Block going out of business before your beneficiary completes a claim, consider setting up a backup method. You can add their fingerprint to your Bitkey and share a copy of your Emergency Access Kit to ensure they have access to your funds if needed.

As part of the inheritance protocol, your beneficiary must store a decryption key to access an encrypted version of your mobile key stored by Block. They need their own Bitkey wallet (app + hardware) to securely store this information long-term and benefit from our recovery protections. Ultimately this is a safety-focused choice in our design - storing keys long-term is hard, and this protocol is based on your beneficiary having a key, not on their government ID or anything like that. And I’ll look into where we might be able to clarify this more/earlier.

Replying to Avatar Gordus

For anyone wondering, I believe this is where keypairs are made:

https://github.com/proto-at-block/bitkey/blob/main/app/core/crypto/src/keys.rs

So now I need to find references to this, but github is claiming there are none 😭

I will keep progress updates on this 🧵

It is frustrating that nobody from bitkey is monitoring this, all other wallet providers I have contacted are very active on 𝕏 and have been very helpful 🤔

Curious how #bitkey will help people stay in control of their funds when they lose part of their wallet? Check out the recovery paper we’ve shared today - and let us know what you think! https://bitkey.build/sharing-our-recovery-design/

Great questions.

On (1): the phone can't modify information signed by the hardware, it just forwards it to the server. Bitkey hardware ships with a key (not the one used for signing transactions) that can be used to sign messages and which Bitkey servers can verify. If a compromised phone attempts to modify what the hardware has signed, the server would know they've been tampered with and would be able to surface that to the user via a channel like email.

On (2): if the Bitkey servers that communicate the addresses or transaction details to you in the proposed solution were compromised, what they show/send you wouldn't match your phone's screen.

Not 100% sure I understand your setup, but seems like probably one of these:

If it’s bluewallet on your phone plus Ledger: If your phone is sufficiently compromised, you can’t trust the address shown in bluewallet, or the QR code you’re scanning..

If it’s desktop plus bluewallet on your phone: if your desktop is sufficiently compromised, you can’t trust the address there, or a QR code scanned from there…

Replying to Avatar RawBTC

I thought Jack had reposted their article from yesterday about seed phrases (https://bitkey.build/seed-phrases-are-sharp-edges/) and responded before I saw it was a new article about hardware device screens.

I don’t agree with all the reasoning in that seed phrase article. Ultimately, someone has to control the seed. If the user doesn’t keep a copy themselves, then they’re deferring trust somewhere else.

“Seedless” custody generally puts a lot of trust in the device securing that seed. Without a seed backup, hardware failures are catastrophic for singlesig setups. I would never do seedless unless it were multisig. But even with seedless multisig, losing a device means you have to deal with a more complicated key rotation process, rather than just recovering the same seed into a new device.

In Block’s Bitkey setup, it sounds like it’s seedless multisig “until you need to export the seed”. It’s yet to be seen how sovereign that recovery can be or if you’ll have to ultimately get permission to access a seed or move to a different multisig coordinator. It sounds prone to lock-in, but I’d need to read more about the technical details to know.

There are trade offs to various approaches, and I don’t think their seed phrase article properly highlights those trade offs.

But like I said, the article Jack linked in the OP is a different topic - hardware device screens. It seems pretty well reasoned, but I only skimmed it. I don’t know if I agree with all the listed attack vectors and risks associated with over-reliance on device screens. I prefer a screen on the device, but screenless might work well enough in their setup, since it’ll have a server-side component to help verify data.

Regardless, it’s a unique approach, and I’m interested to see how it develops. Will probably be a good onboarding option for less technical people.

Thanks for the feedback! When we share details of the key portability feature I’d love to hear what you think. You’re right that in multisig there are ways to recover from losing a device without needing the seed, and we’re trying to make that easy for the owner to do using the other device in the multisig setup. You can read more about this in another one of our posts: https://bitkey.build/losing-your-keys-without-losing-your-coins/

Don’t think you need a screen on the hardware (or the “server as a screen” option) to check for clipboard malware - you can catch that on the device you’re doing the copying on

Our final post in this week's security series is a big one: why screens aren't all they're cracked up to be, why we think they keep people from self-custody, & how Bitkey can help without a screen on the hardware. Take a read, let us know what you think: https://bitkey.build/screens-are-not-a-panacea/