A16z Crypto criticizes ZK for abuse, Jolt upgrade brings true privacy

Renowned venture capital firm Andreessen Horowitz’s Web3 division, A16z Crypto, raises thought-provoking questions in its latest blog post: most virtual machines (zkVM) labeled with “ZK” do not actually provide true zero-knowledge privacy protection. Jolt zkVM also sharply criticizes the systemic misuse of the “ZK” term within the crypto ecosystem.

Misuse of the ZK Label: Why Most zkVMs Are Not Truly Zero-Knowledge

A16z Crypto reveals a widespread but rarely publicly addressed issue: “Most zero-knowledge proof virtual machines are not truly zero-knowledge—unless an expensive ‘wrapping’ process is applied.” They explain that this wrapping involves recursively verifying zkVMs within another ZK proof system, which is computationally costly and often requires sacrificing transparency (i.e., introducing trusted setup).

The fundamental problem lies in terminology deviation: “‘ZK’ has been widely used as an abbreviation for ‘succinctness,’ meaning ‘short and easy to verify’ proofs, rather than genuine zero-knowledge privacy.” A16z Crypto warns: “As community concern for privacy grows—demanding true zero-knowledge, meaning the privacy of sensitive data of the prover—this misuse of terminology is becoming a real issue.”

Three Common Confusions of ZK Terminology

True Zero-Knowledge (True ZK): Proving a statement is true without revealing underlying information, protecting the privacy of the prover.

“ZK” as an abbreviation for succinctness: Most zkVMs focus solely on “short and easily verifiable” proofs, not on privacy.

Wrapping schemes: Using recursive proofs to add true zero-knowledge, but at high computational costs and usually requiring trusted setup, thus sacrificing transparency.

Jolt zkVM’s Solution: NovaBlindFold Folding Scheme

In response to these issues, A16z Crypto announced an important update Tuesday for the open-source project Jolt zkVM, introducing the NovaBlindFold folding scheme to natively support zero-knowledge functionality.

Folding schemes are a cryptographic technique dating back to the 1990s. A16z chose this method to replace costly recursive wrapping schemes. NovaBlindFold creates “Blind Proofs” to prevent information leakage, offering high efficiency—resulting in a ZK proof size of only about 3KB compared to the original non-ZK Jolt proof—making it suitable for privacy applications.

This upgrade comes amid a renewed focus on privacy within the crypto ecosystem. Digital Currency Group CEO Barry Silbert recently indicated that significant funds are expected to flow into privacy chains. Institutional investors’ concerns over the full transparency of most blockchains are driving the industry to seek more reliable privacy solutions.

Frequently Asked Questions

Q: Why does A16z Crypto criticize the ZK label?
A16z Crypto points out that “ZK (Zero-Knowledge)” has become a widespread abbreviation for “succinctness” in the industry. Most zkVMs do not provide genuine zero-knowledge privacy protection unless they employ costly, trusted-setup “wrapping” schemes. As privacy demands grow, this misuse of terminology is becoming a real obstacle to industry development.

Q: How does the NovaBlindFold folding scheme address this issue?
A16z’s Jolt zkVM introduces the NovaBlindFold folding scheme, enabling native zero-knowledge privacy without expensive recursive wrapping. It creates “Blind Proofs” to prevent information leakage, with only about 3KB of additional space overhead, balancing efficiency and true privacy.

Q: What is the fundamental difference between true zero-knowledge and “ZK as a succinctness abbreviation”?
True zero-knowledge means the verifier cannot infer any private input data from the proof; “ZK as a succinctness abbreviation” only emphasizes that the proof is short and easy to verify, without involving privacy protection of underlying data. The two have an essential difference in cryptographic meaning.