Hi Everyone! I'm Jeremy Rubin a long time bitcoin dev and advocate for BIP-119.
I currently work on judica & Sapio for bringing enhanced smart contracting to Bitcoiners with a focus on scaling, decentralization, self custody, and privacy.
AMA
What are the privacy use-cases for CTV on Bitcoin
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There are quite a few, but off the bat:
  1. Payment Pools represent a technique for CoinJoins with "lazy output creation" where the pooled funds can be kept as a single coin which does iterative (on-chain) updates to make payments on-chain. Update data only has to be shared with your hierarchical neighbors with CTV, so you get some better privacy v.s. other techniques.
  2. PathCoin is a novel concept for a coin that is off-chain transferrable amongst a group of N users with only the sender/receiver (2) having to communicate (v.s. lightning which requires N of N online)
  3. Non-Interactive Batched Lightning can make channel opening hidden until close, with opportunity for cooperation (pairs with Payment Pools)
What are some of the Bitcoin smart contract applications you're most excited about?
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Personally I am really excited about Payment Pools as a Big New Trend™ for Bitcoin, especially with majority rules (v.s. unanimous) on txns, since those look like DAOs. Love em or hate em, I think DAOs as vehicles for capital formation and management is really exciting, and something I'm looking to spend more time making infrastructure for.
Generally, I see current users excited about Vaults since self-sovereign security is a huge deal, and CTV represents a non-marginal improvement to what can be done today.
Non-interactive lightning channels are a super straightforward improvement for lightning companies who oboard many users.
Lastly, the DLC research Lloyd F posted about recently makes DLCs a lot more practical with CTV, which I think is also highly exciting.
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Interesting - are there any particular companies or groups of users who you think would be quick to adopt Payment Pools?
Trying to wrap my head around some of the emerging use cases for them...
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I think that I could see a Payment Pool from wasabi/samurai since it can be closely related to CoinJoin.
but from a company perspective I think that lots of businesses (e.g. exchanges?) might connect their hot wallets into payment pools to streamline cut-through between exchanges with higher value caps than might be comfortable for e.g. Lightning.
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Had a few more unrelated questions...
How healthy is the Bitcoin and Lightning developer ecosystem?
Are you seeing fewer/more talented people begin building on Bitcoin than in past years?
Are you noticing more development activity moving onto Lightning?
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IMO about as healthy as an anemic 3rd degree burn victim with long covid :)
Right now, you can leave your Google job and raise a seed/pre-seed of $1-5M at a $30-50M valuation to build on Ethereum.
You'd have to be nuts to -- on purely financial motives -- decide to work on Bitcoin instead.
That's OK because we don't want the merc's, we want passionate dedicated individuals, but consider if you're trying to build a bitcoin company and that is the ability to pay for talent you have to compete with. It is going to suck.
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I'm also interested in DAOs and sidechains, but am a layman, my technical knowledge is pretty shallow.
If OP_CTV and Anyprevout are implemented, which I think are the requirements for something like a spacechain, and later we do what Russell O'Connor was saying here: https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2022-January/019813.html and implement TXHASH + CSFSV as a more generalized approach. Could those sidechains be moved to the new code relatively easily?
I ask because while I agree with you that we shouldn't wait two years to wait two more years to wait two more years to do the perfect thing. But, I don't have the technical knowledge to pontificate on a theoretical sidechain migration.
(side note: I wrote a randomly really long post about error correction and innovation in Bitcoin on the UnHashed podcast telegram group about this, lol--The topic comes up on their most recent podcast (ep 147 like 30 minutes in)---this post here is a much simpler/casual version of that).
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Wrapping this up: feel free to ask more stuff, will respond later!
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Have you had any success getting help developing sapio and sapio studio or does it remain a solo effort?
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There's definitely growing interest, but TBH I could use a lot of help building a team to develop it... as you can imagine, the intersection of qualification, interest, and ability for me to pay for such devs competitively leaves a tiny set of people.
If I had beacoup bucks this would be easier to solve, but I don't. It seems like it would make sense for me to have that funding, but it's been uphill battle for whatever reasons.
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Hey Jeremy! It's great to have you here!
What is the mainstream media narrative/framing that you hate the most and how should we frame it instead?
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I'm assuming you mean "bitcoin specific" and "jeremy rubin specific"... not sure anything happening in my world is mainstream.
I'd say that one thing that bothers me is that people think that I am advocating for CTV thinking it's some perfect supergenius design and everything else is Bad™. The reality is that I think CTV is a viable engineering/community Schelling Point for improving Bitcoin and I'm unsure of what would be better in that regard! I.e., I know there are limitations, but I think BIP-119 represents a low technical risk moderate benefit improvement, but I don't think it solves all problems.
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addendnum: in terms of framing, I'd like to see Bitcoin development have a more pragmatic small-step improvement process that works agressively v.s. building big complex overhauls, and I think CTV is a good representative of what that process could look like.
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Thank you for the insight and I appreciate your work towards enabling CTV!
For this question I meant more generally about any topic you see in the media - e.g. about privacy, about Bitcoin, about economy, about people... (I'm sorry if this is a question too out of scope :) )
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eh yeah a bit out of scope...
but it is an AMA.
So let's go with narratives around decreasing the population growth and stuff... I think that consciousness is like the scarcest asset (scarcer than Bitcoin ;) in the universe and as a species it's incredible we can make more of it, so we should be dedicating a lot more energy into figuring out how to sustain 10x the number of people v.s. fighting about little stupid NIMBY issues.
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Another questions: Would it make sense for all personal wallets to implement inheritance feature (e.g. when not touched for 10 years, it automatically goes to family wallet...)?
What is the best approach to handle inheritance in Bitcoin?
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Well I think what is good about CTV is that it is incredibly explicit with exactly what should happen with each coin you have, so it's relatively easy to model (you know all state transitions!) for wallets. Anything more sophisticated ends up being harder to reason about, by quite a lot!
I think I would want all of my wallets to have this feature... so yes?
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Favorite taco?
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Depends on the shop. If it's an average place, pollo asado is usually my go-to, but at a good spot a baja fish taco is unbeatable.
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What are the biggest obstacles that your team had to overcome to reach (close to) universal support? Is there any specific holdout/opponent that's preventing BIP-119 to be approved?
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there's not really a "team", it's just me and folks who like the concepts.
I think the biggest tension right now is w.r.t. soft fork processes:
Are soft forks themselves (not the upgrades contained in it) much riskier than the upgrades?
If the answer is "no" then there's pretty wide support for CTV... if the answer is "yes" then people think waiting for us to make the most impact for this ultra high risk process keeps ctv "below the line" of value add.
I don't think there are any current NACKs of the form "this would be, absent costs of doing any fork, bad or technically unsafe for Bitcoin". Or in other words: would Bitcoin be OK if this were a feature that was always in Bitcoin? Trying to reframe the question of not if we should add it, but would we want to remove it were it already there is useful for reasoning about if you think it is unsafe or bad. E.g., OP_CODESEPARATOR in legacy script is something that we might want to remove were it not already there.
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Will we have twitch sessions to learn more about CTV with screen sharing, audio and chat?
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i've done twitch sessions before and they had really poor engagement compared to other formats.
maybe if someone with more of a twitch audience wants to host/do a takeover, otherwise it's a high-effort low reward format for me...
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  1. Are you aware of any abuses of covenants in the altcoin space that BIP119 would also be vulnerable to?
  2. From an outsider perspective, it seems frustrating to do core development. What's the most surprising thing you've learned while trying to get an ambitious proposal in core?
  3. What's something you believe or foresee in Bitcoin's future that nearly no one else, including the most bullish bitcoiners, don't believe?
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  1. Not in particular. Would you call any contract happening in Ethereum (arbitrary powerful system) an abuse? Generally these things are opt-in. Also we already have issues that users can create (e.g. wrt to consensus incentives in Bitcoin) without covenants... not too worried here :)
  2. No comment really, nothing particularly surprising if that makes sense. Your assesment is correct though.
  3. I think in the long run we will never see major ossification. Security in Bitcoin rests on economic demand of on-chain space, so we will constantly have to ensure Bitcoin is serving as the settlement layer of record. That, and at a implementation level, security is an ongoing concern. I think there are bigger risks in implementation stuff v.s. the spec/protocol level, so I don't suspect we gain much from protocol ossification either. IMO even things like PoW are on the table -- my ongoing question is are we getting the best security/censorship resistance for the best price, and I would be surprised if in 50 years we haven't improved on that (imagine computers from 50 years ago and thinking that today's computers would be similar).
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On 2, you seem to have made the most progress of anyone wrt to getting an ambitious proposal in core. I suspect future core devs will be able to learn a lot from you in this regard. That was the motivation behind the question at least.
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i hope the lesson is not "this is so hard it's not worth trying again".
that might be my personal takeaway, sadly.
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  1. Are you going to be doing a Pleb Fi in Miami again this year?
  2. If people are interested in seeing BIP119 in core, what are the highest impact things they can do to help you?
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I am just learning Bitcoin as a beginner in Python, is there a tutorial I can get started with writing an application with Sapios as a complete beginner? Thank you, This will help in learning by doing :)
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howdy!
check out https://learn.sapio-lang.org to get started, there's also a ton of content in https://rubin.io/advent21
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Jeremy - I am a devout bitcoin holder and am worried about the lack of innovation in bitcoin relative to all the alt-coins being developed today. How can we accelerate Bitcoin innovation without compromising the critical foundations of bitcoin - security, de-centralization, etc.?