Sean Bowe on Tachyon and the Evolution of Zcash

Anna Rose introduces Sean Bowe, a Zcash core developer and lead on Tachyon, discussing the evolution of Zcash since 2020. They highlight the technical roadmap, particularly the implementation of Halo and its impact on Zcash. Sean reflects on his nine years at the Electric Coin Company (ECC) and his focus on scaling and crypto research after leaving. He acknowledges ECC's progress, especially with the mobile wallet, Zashi, which underwent significant engineering work.

The conversation reveals a lull in communication within the Zcash ecosystem from 2020 to the present, despite ongoing internal efforts. After launching the Orchard project, Zcash faced a spam attack that exposed vulnerabilities, prompting a year-long effort to address these issues. Sean emphasizes the importance of improving user experience for mobile payments, recognizing usability as crucial alongside cryptographic advancements.

As he continues to be involved with Zcash through Tachyon's development, Sean clarifies that the focus remains on enhancing usability while iterating on Zcash's features. The ECC's focus has shifted from protocol research to addressing immediate issues, with a grassroots team working on Tachyon to enhance Zcash. Tensions between ECC and the Zcash Foundation have characterized their past interactions, but there is a noted positive shift in the community.

Tachyon is introduced as a significant upgrade for Zcash's shielded pools, which facilitate private transactions but require improvements due to slow initial cryptography. The upgrade process involves migrating funds and enhancing privacy, with a focus on mobile proofs that enable mobile wallets. The Orchard protocol, utilizing Halo 2, plays a crucial role in Tachyon, aiming to improve scalability and address cryptographic bottlenecks without requiring user intervention.

Sean discusses the development of Halo 2, which incorporated KZG polynomial commitments, and the importance of eliminating trusted setups to enhance Zcash's accessibility. Challenges faced during the development of Orchard and Halo 2 included practical engineering issues, particularly with wallet synchronization and transaction processing. Plans for Tachyon aim to release the shielded pool by late 2026, with wallet support being developed concurrently.

The current state of Zcash and its shielded pools is addressed, with an estimated value of $4-5 billion. Initially, only about 2% of ZEC holders utilized the shielded pool, but this has increased to approximately 30% due to improvements in user experience and performance. Key improvements included hardware wallet support and simplified address management, which alleviated confusion for users.

The conversation touches on Zcash's potential integration with other ecosystems, particularly through cross-chain payments. Bridging in cryptocurrency is examined, emphasizing the effectiveness of bridges relying on trust in the service for executing swaps while allowing users to maintain custody of their funds. Governance and voting within Zcash are also addressed, noting increased involvement of coin holders in decision-making.

The evolution of the Zero Knowledge (ZK) ecosystem is discussed, reaffirming Zcash's commitment to privacy. The current political climate is seen as more favorable for discussing zero-knowledge protocols. Sean confirms that Tachyon builds on cryptography from Orchard, designed to be recursion-friendly, and expresses interest in using recursive proofs to enhance Zcash's scalability.

The podcast highlights ongoing challenges in designing privacy solutions within cryptocurrency, with Tachyon addressing these through a recursive proof and evolving nullifier model to prevent double spending while minimizing the need for validators to store all nullifiers. The conversation concludes with a discussion on the need for a new architecture in Tachyon to achieve full privacy and scalability, utilizing the original Halo construction alongside recent advancements.