Ethereum co-founder Vitalik Buterin has weighed in on the ongoing debate about privacy technologies in blockchain systems. His comments followed a post by ZCash researcher c-node, who highlighted limitations of multi-party computation (MPC), fully homomorphic encryption (FHE), and trusted execution environments (TEEs) compared to ZK systems.
Buterin Clarifies the Limits of Zero-Knowledge Proofs
In a post on X, c-node wrote that while MPC, tFHE, and TEEs can enable private applications not achievable with ZK alone, their privacy strength remains weaker. The researcher advised developers to use pure ZK for use cases like payments, transfers, and voting whenever possible.
Buterin responded, saying ZK proofs cannot handle certain privacy requirements, especially in voting scenarios. "For voting, ZK does not offer coercion resistance," he explained. "You do need a trusted party, MPC, FHE, or TEE for that."
He added that developers could enhance privacy and resilience by layering technologies. "You can layer ZK and FHE together so that even if FHE breaks, you still have every property except coercion resistance due to ZK," Buterin said.
According to him, stacking cryptographic tools creates a defense-in-depth approach. He noted that ZK proofs can secure core privacy guarantees, and complementary tools like FHE or TEEs can address specific weaknesses, such as preventing voter coercion or maintaining secure computation.
Debate Over Layered Privacy Systems
The discussion continued when another developer, Nitanshu, joined the thread, highlighting potential risks in combining ZK and FHE. He noted that while the hybrid model proves computation integrity, collusion risks remain. "Nodes can still collude and try decrypting the ciphertext," he said.
Nitanshu proposed running nodes within a trusted execution environment as a way to increase coercion resistance. He also suggested removing decryption keys altogether, though he acknowledged that such methods are not yet practical for general computation.
Buterin replied, clarifying that ZK proofs play a broader role than ensuring computation accuracy. "The point of ZK is not solely integrity," he said. "It’s to anonymize the voter identity client-side."
He explained that coercion resistance mechanisms, such as allowing duplicate votes but counting only the first or last, operate within the FHE or TEE layers. These components, he said, rely on "nullifiers," which anonymize identity data without exposing voter details.
Buterin’s remarks point to a tendency in cryptographic research that encourages combining several privacy frameworks instead of depending just on one. The complexity of privacy requirements is increasing as decentralized applications spread into governance, voting, and finance.
ZK systems provide strong mathematical privacy, but technologies like FHE and TEEs add operational features that ZK alone cannot deliver. These include protection against user coercion and secure computation over encrypted data, both essential requirements for practical adoption.
Buterin’s comments are also in line with Ethereum’s more general research focus, which continues to place a high premium on privacy. The Ethereum Foundation and its partners have continued funding projects exploring advanced ZK rollups, encrypted mempools, and cross-layer security models.
While no single technology has achieved perfect privacy, developers are increasingly using layered solutions that integrate the advantages of several different systems.