A New Chapter for Zcash
Sean Bowe on Tachyon, recursive proofs, and lessons from the last decade
After our winter break, we returned with a new episode of the Zero Knowledge Podcast focused on Zcash - the original OG ZK project. My guest was Sean Bowe, a long-time Zcash core developer whose work has shaped some of the most important ZK systems in production. It seemed like a very good time to reconnect with Sean and catch up on the Zcash story!
It’s also been a long while since Sean was on the show, and a lot has happened since our conversations back in 2020. And so, we had a chance to dig into what’s changed in Zcash, how the years of research and firefighting fed into today’s roadmap, and what Sean is now building with Tachyon, the next major shielded pool upgrade for the network.
What stood out to me in this conversation was how much had been happening around Zcash that I had been unaware of. Sean gave us the inside scoop on the launch of Orchard, including the long and difficult time after the launch where the team was fighting fires rather than exploring cutting edge ZK research. While that period for Zcash may have looked quiet from our corner of the ZK ecosystem, Sean explains that it was pretty chaotic inside the ECC and within the Zcash community. What came out of this was a renewed emphasis on UX, wallet design, and real-world usability for Zcash. We can see the impact of these changes today with the rise of mobile wallets like Zashi as well as the recent increase in shielded pool usage.
Highlights from Episode 388
Sean gave us insights into Zcash’s evolution since 2020 both inside and outside of the organization building it.
He explained how Zcash’s shielded pools evolved from Sprout to Sapling to Orchard, and how Tachyon continues that lineage while targeting scalability bottlenecks that have existed since the earliest Zcash designs.
We revisited the story of Halo & Halo2 and discussed how components of these were integrated into Zcash.
Sean shared how he has been exploring a technique where off-chain workers can help reduce the nullifier state bloat without relying on pruning, while remaining fully privacy-preserving and non-custodial.
We talked a lot about UX tradeoffs: where Zcash was at in 2020, how far it has come, why today’s experience is may be tricky to scale long term, what might still have to change, and how Zcash is trying to keep those changes as seamless and invisible to the users as possible.
Governance also came up, including how Zcash has shifted toward more coin-holder signalling and private voting, something that can now influence protocol priorities going forward.
Sean shared that he doesn’t think Zcash should try and be a multi-asset DeFi platform. Instead, he argues for Zcash as “dumb money done really well”, so focused on private payments, minimal surface area, and rigorous cryptography.
We also recorded a bonus segment for zkMesh+ subscribers, where we zoomed out and talked about Sean’s thoughts on quantum computing and ZK. In it, he shared his thoughts on how serious the quantum threat really is for privacy systems, what kinds of cryptography might age better than others, and how teams like Zcash think about long-term cryptographic risk when designing systems meant to last decades. To access this, you need to become a paid subscriber - you can do so here!
Zcash is a foundational project in the story of ZK, as the first fully ZK-focused blockchain, and the team behind it has contributed an enormous amount of meaningful research and breakthroughs over the years. It was great to get an update on where the project is today, and to see how years of operational experience, mistakes, and tradeoffs have shaped a more mature, battle-tested network. Excited for the upcoming Tachyon upgrade - planned for later this year!
Be sure to check out Episode 388: the full episode page is here, or follow this thread for commentary.
Talk soon,
Anna
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