Design mockups for a V1 of the app

[GBKS]

Per recent conversation, we want to add multisig to the app and polish the user experience. I am creating this issue to have a central go-to point for the design progress, which will primarily happen in Figma in this file.

The goal of the V1 is to build a good user experience with the existing and new features (really just multisig), but still keep things as simple as possible. Multisig will be limited to Coldcard, so this feature will need to be evolved over time anyways.

Requirement for the V1 design:

• Mock-ups for all screens in the app
• Use a style guide for all elements (colors, icons, buttons...)
• Some light MyMattress branding elements
• Reviewed and approved by the team (technical and user experience)

Feel free to leave comments in Figma directly on the designs (press "C" to enable comment mode).

The Figma file is the one for the Bitcoin Wallet UI Kit. Using that as a base helps get started more quickly because a lot of the needed components are already done. Plus, it helps tighten up the components in the kit because I will need to get them ready for IRL use. It also means the look is a bit generic right now. We can lift out the app design from the kit later if we want to make it more unique.

My goal is to finalize the design by mid-February.

Scope and decisions:

• Multisig will be via Coldcard only
• No contacts, transaction labeling or other user data options
• Allow users to have two wallets or force a single wallet? Single wallet makes the UI easier, but also makes the app useless when out-and-about on a multisig wallet

[tanx]

Awesome! I'll add my thoughts in Figma.

Multisig will be limited to Coldcard, so this feature will need to be evolved over time anyways.

This makes sense to me given ColdCard's new on-device address verification support for multisig wallets. Plus ColdCard is liked and used by many Bitcoiners already. I've also been playing around with CoboVault. It supports on-device address verification of multisig wallets as well. So I think both are low hanging fruit options for a mobile-only multisig mvp. The advantage of CoboVault over ColdCard is that you don't need an additional lightning-connecter/SD-Card adapter for your iPhone and can just hold your iPhone over Cobo's screen to scan/pass QR codes. @ConorOkus pointed out that the passport device has a compatible QR code interaction model. We can stick with ColdCard for now. Just something to keep in mind.

[tanx]

Since @GBKS pointed out we should document the security requirements for a hodl app, here are my initial thoughts. Feel free to add/discuss these points:

• small attack surface (simple mobile app, hardware wallet support)
• high redundancy (2-of-3 multisig with two hardware wallets and one mobile key backed up to the cloud)
• multi-vendor security (e.g. support for ColdCard and CoboVault)
• Audit-ability of receive addresses (provide step-by-step guide of how to verify addresses on HW screens)

[moneyball]

Additionally could provide guidance on locations to store hardware wallets and associated tradeoffs (eg same or dispersed geographic location, bank safe deposit box vs. personal safe, etc.). (this should also wind up in the design guide)