From Zerocoin to zk-promises
Ian Miers on zkSNARK for payments, identity, & reputation
In this week’s episode of the Zero Knowledge Podcast, Nico and I chatted with Ian Miers. Ian is an Assistant Professor at the University of Maryland and the co-author of the foundational Zerocoin and Zerocash, among other influential ZK works. It’s been a long time coming to have Ian on the show, and I was so happy we finally made it happen!
To kick off our conversation, we revisited ZK research from 2011–2015 — those formative years when zkSNARKs were first being formalized and people like Ian began experimenting with them in a blockchain context. Together with his advisor at Johns Hopkins University Matt Green and colleagues Christina Garman and Aviel D. Rubin, Ian co-authored the Zerocoin paper, the first attempt at that combination. He describes Zerocoin as something like a ZK sidechain for Bitcoin, which wouldn’t really have been feasible at the time, but was inspiring all the same. Later came Zerocash, which built on the newly published zkSNARK construction from Ben-Sasson, Chiesa, Tromer, and Virza, and was designed as a standalone zk-based blockchain. This work ultimately led to the creation of Zcash, the first major ZK-focused project. Ian shared a funny detail about how that collaboration came together: two research teams were simultaneously and independently developing the precursors to usable zkSNARKs, and his group could have worked with either. The deciding factor? Only one of the teams replied to Ian’s email — and that’s who they ended up working with.
Key takeaways from Episode 378
Zerocoin (2013) and Zerocash (2014) laid the foundation for private payments on blockchains, leading directly to Zcash.
Trusted setups were once hugely controversial and incredibly challenging to perform in a trusted manner, but innovations like Powers of Tau, parallelisation and universal setups made them scalable and less contentious.
Ian worked on ZEXE, which introduced a model for private smart contracts, later forming the basis of projects like Aleo and influencing Aztec.
He also worked on zk-creds, a concept that was initial ignored but has become more and more relevant in the last 18 months. It is built on earlier ideas of anonymous verifiable credentials, but proposes a ZK-based identity system.
zk-promises, Ian’s newest work, explores programmable, anonymous reputation with callbacks — a step toward tackling challenges like compliance, sybil resistance, and adaptive trust.
On-chain reputation is a balancing act. On one side, you need to track and weed out bad actors; on the other, people deserve second chances and the ability to repair their reputation. A robust reputation system shouldn’t be vulnerable to permanent damage by malicious actors.
Ian stressed that tools like zk-creds and zk-promises are powerful, but their impact depends on how responsibly they’re applied.
A few times during the show, we mentioned that we were running out of time, since we could see that the list of topics we wanted to get to was so long, and the remaining time was so short. After recording, we even kept the conversation going about specific ZK projects, AI, quantum, and other cutting-edge work. I definitely hope we can bring him back soon to dive deeper into more of these areas.
Be sure to check out Episode 378: the full episode page is here, or follow the thread for commentary.
Talk soon,
Anna
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