[Ar-Curunir]

> Moreover, the serious cryptographers working on anything related to blockchains have more or less stopped talking about the permissionless setting (where Bitcoin, Ethereum, and basically all of the popular blockchains in use are) because security is too hard to define in a meaningful way.

This is untrue, I see far more work on the permissionless setting (including formalizing definitions) than on the permissioned setting on ePrint. This includes respected cryptographers Like Elaine Shi, Rafael Pass, Silvio Micali, Andrew Miller, Aggelos Kiayas, and more.

> Meanwhile, academic and (non-blockchain) industry researchers have been pushing the state of the art in every subfield within cryptography, ZKPs included. Big companies have been deploying MPC as a means of addressing privacy concerns and regulation, and the cryptographers working on that (full disclosure: I am one of them) have been pretty active in publishing their work

While cryptography is certainly a much bigger than zkps, it is also absolutely true that, for the metric of “deployable protocols”, the pace of zkp innovation has far outstripped the pace of MPC innovation over the past few years. I say this as a cryptographer with a bunch of non-zkSNARK papers; my general-purpose zkSNARK work has been deployed, adopted, and obsoleted in the span of ~2yrs, all while my MPC work in the same span hasn’t inched towards deployment (despite being sufficiently practical for deployment), and follow up work has provided only marginal improvements.

> Beyond the ZCash and a few other groups with serious cryptographers the blockchain space is a desert in terms of interesting cryptography.

That’s incorrect. Beyond ZKPs, there’s been blockchain-inspired-and-funded work on Verifiable Delay Functions, threshold signatures, signature aggregation, anonymous gossip networks, fuzzy variants of PIR, functional commitment schemes, set accumulators, coding theory, and more.

[betterunix2]

That is an impressive list of cryptographers working on blockchains, but at major cryptography conferences there is less and less blockchain work being presented, to the point where CRYPTO'21 didn't have any blockchain sessions at all, while EUROCRYPT'21 had a single session where blockchain work was combined with work on privacy and law enforcement. To be fair, three sessions at CCS'21 were dedicated to blockchain research, but CCS is structured to allow more topics, it is not a conference specific to cryptography, and they had two sessions dedicated to MPC and a third on federated learning which touched on MPC. It is a small sample but representative of a larger trend of cryptographers becoming less interested in blockchain research.

I have not seen ZKP innovation outstrip MPC innovations at all. In the past decade I have seen a rapid expansion of research in MPC following both a strong push by DARPA and growing interest among large tech companies and banks. There has been a revival of interest in set-intersection protocols and related functionalities, a lot of impressive work in garbled circuits and other generic protocols that have greatly reduced their resource requirements, machine learning applications, and various other ongoing lines of work. At worst I would say that ZKP and MPC research have been roughly equal in terms of the pace of innovation, which should surprise no one as the two topics have strong connections.

Moreover, while there is certainly a lot of ZK research being published year after year, most of it has nothing to do with blockchains and is not coming from anything related to blockchains. There are plenty of academic researchers publishing ZK work, and I still see lots of industry ZK research that has nothing to do with blockchain. The same is true of all the other topics you mentioned -- some blockchain-inspired work here and there, but a lot more research from elsewhere.

Sorry to hear that your MPC work has not made it into production, but maybe that is because it is not as practical as you claim. Personally I like to say that the only test of "practicality" that matters is whether or not it is useful in a real-world application. Obviously your SNARK work cleared that bar, which is great but does not really say much about the pace of innovation. I can say that most of my published research at this point has been put into production -- an equally meaningless statement since I have been working for a big tech company for a long time, and the research I have published in that time has all been the result of work I did to address various privacy and security problems that company faces. My judgement of where the innovation is happening is based on the research I am seeing people present at various conferences. Maybe I am looking in the wrong places, and there is actually a whole world of cryptography conferences where people are excited about blockchain work?