 What is your opinion on directed acyclic graph? Does it truly have the potential to replace open and decentralized blockchains, or is it vaporware? I don't think the question is an either-or. I don't think directed acyclic graphs, tangles, or other similar formulations can replace proof-of-work, open, decentralized blockchains. I think that's because proof-of-work brings some very specific and very valuable characteristics that simply cannot be achieved with other consensus algorithms, or at least no one's been able to demonstrate at scale, achieving those with other algorithms. Immutability is a big issue there. The ability to change history without anyone noticing, or without the recent entrance into the network of being able to detect a false history from a true history. But more broadly, I think that proof-of-work with anonymous participants in an open, decentralized network makes a cryptocurrency very resilient to coercion, very resilient to controlling regulations, and very resilient to censorship. And I think those are very, very important capabilities. The technologies that I have seen that use directed acyclic graphs are essentially a mixture of either proof-of-stake or proof-of-authority systems, proof-of-stake where the control of the network is based on staking the currency. And we have yet to see proof-of-stake being demonstrated at a scale, and under duress of authorities, to the point where it can prove to remain decentralized and censorship-resistant. More importantly, I think proof-of-authority, which is what you see in some blockchains, and from what I understand, for example, IOTA, is where you have vetted nodes that are trusted, and that's not decentralized, that's a centralized system. And centralized systems are susceptible to coercion and censorship. So, once again, there are many people who bring evidence of the new best thing since Bitcoin, the latest improvement since Bitcoin, something better than proof-of-work. This isn't new, this is something that's been happening almost since the beginning of Bitcoin. As soon as people saw that this was valuable and viable, copycats emerged, and various people tried to find other ways of doing the same thing. Now, that's not a bad thing, that's great, that's where innovation comes from. So far, nobody's been able to show a system that can replace proof-of-work and still maintain the same imutability guarantees, or a system that can replace decentralized open mining and proof-of-work, and remain decentralized and not depend on centralized actors. And when you have a centralized system, it may look the same at first. But once you have a lot of value and a lot of interesting applications running over that, there will be increased pressure, coercion, and censorship pressure by governments. The real test is whether you can resist that. I think direct-to-cyclic graphs are interesting, but I don't think they have the potential to replace open and decentralized blockchains. That doesn't mean they're vaporware, though, so it's not an either-or question. They're simply an alternative consensus mechanism. If you don't have decentralized proof-of-work mining, you don't really need blocks, you can just chain transactions together, which is the basis of direct-to-cyclic graphs. But in my opinion, you've sacrificed something, and what you've sacrificed is decentralization.