3. Just a little longer than half a year ago I stated that Unless both Ark implementations fumble the ball, Spark is going to eat everyone's lunch. and today we are seeing that Spark has gotten a big headstart by becoming the defacto Lightning backend to many self-custody wallets, how do you guys think you will be able to reclaim the room taken by it? In the end the main reason why is has been implemented is because it simply works and it is very simply to implement in a wallet, what's your response as a product?

While Spark did have a head start, we see that they are focussing a lot on stablecoin payments and other tokenization things where security trade-offs are inherent to the currency used.

We don't think the Spark model fits the bitcoin ethos particularly well. When you run a Spark-based wallet today, you still get in big trouble if the Spark entity disappears and can get totally rugged if the entity is actively malicious.

Bark is built with the bitcoin ethos as our central guidance. Our client is user-first, with protections against malicious servers built into every interaction. When an Ark server disappears or becomes malicious, Bark users will be fine and have their funds properly exited onchain.

In the end, this is what bitcoiners expect from a bitcoin wallet.

1. While working on Bark with the current consensus rules, what has been for the team the biggest challenge so far?

The original Ark protocol was based on CTV, but CTV eventually didn't get adopted by the bitcoin community.

By using CTV, the original designs for Ark had very limited interactivity requirements from the users. Users only had to deal with the server.

Without CTV, we had to replace all covenant usage with what we call pseudo-covenants that are enforced by multisigs with all users that are affected by the policy. This introduces a loooot of interactivity work. Users need to be online at the same time to sign lots of bitcoin transactions.

It forced us to make some trade-offs to make this work for mobile wallets as well.

We're happy with the way it turned out, but we would definitely have been able to launch 6 months earlier if we had CTV :)

2. I've seen you guys making the impossible possible by finding a way to bring hArk to life without needing CTV or Covenants in general or finding a way to (almost) decentralize operations, so the concrete question is which of the innovations done by Bark is the most important in the team's opinion?

Definitely think that our main contributions were in realizing that the original Ark protocol wasn't finished and going back to the drawing table. We came up with several new designs for Ark-like protocols and implemented a (covenant-less) variant of one of them: hArk. We intend to implement Erk or something similar in a covenant future.

We also recognize that the design space for such protocols is still very much open. When trying to implement a specific instance of a protocol, tunnelvision is a real effect. Someone with the capacity to take a step back and go back to the drawing board again, can probably come up with many new interesting ways to improve.

5. Why is Grubles naked in his profile picture?

It's a side effect of being so excited about Bitcoin payments.