The Nexus zkVM, Explained

In the fourth episode of Exponential, Samuel Judson—head of zkVM engineering at Nexus — joins the show to unpack the science, strategy, and systems thinking behind zero-knowledge cryptography. 

Sam brings a rare combination of perspectives: part mathematician, part systems engineer, and deeply attuned to the social and regulatory dimensions of cryptographic technology.

This primer-style episode traces the evolution of zero-knowledge proofs, the motivation for building a zero-knowledge virtual machine (zkVM), and why ZK is becoming foundational to how trust is engineered into software systems.

At its core, zero-knowledge cryptography enables a striking concept: proving something is true without revealing why it’s true. Sam traces this idea from its origins in theoretical puzzles — like verifying a password without exposing it — to today’s full-fledged systems capable of verifying complex computations without revealing any underlying data. 

As he puts it,

“It started as a privacy technology, but today, ZK is also a scaling and verification technology.”

One practical example comes from healthcare. Hospitals handling protected patient data can process it through certified de-identification programs running inside a zkVM.

The result is a cryptographic proof that the program executed correctly — without the system ever revealing or leaking the sensitive inputs. In Sam’s words, “You get the best of both worlds — you can keep protected health information private while giving researchers strong guarantees about how the data was processed.”

This turns ZK into more than just a privacy tool — it becomes a powerful mechanism for regulatory compliance and institutional trust.

Using Coding Agents for zkVM Guests: Applications to Accountability

In this post we’ll take a look at using the Cursor coding agent to implement a guest program for HIPAA safe harbor compliance.

NexusSamuel Judson

That leap — from proving static statements to proving the execution of full programs — is the promise of the zkVM. At Nexus, the engineering team simulates a RISC-V processor within the zkVM, enabling developers to compile their existing programs and generate proofs of correct execution. 

This universality, Sam explains, eliminates the need to write bespoke cryptographic rules for each use case.

“Instead of writing new cryptographic rules for every type of proof, we simulate a CPU and prove it behaves correctly. That gives us universality.”

Beneath the surface, three engineering pillars determine whether a zkVM is viable: efficiency, soundness, and usability.

Efficiency is critical, given that zero-knowledge proofs are inherently more expensive than native execution. Soundness ensures the system only produces proofs of true statements — anything less would break the entire trust model. 

And usability means that developers can access the technology without needing a PhD in cryptography.

“You can have the fastest prover in the world, but if it’s not reliable or easy to use, it’s not meaningful.”

So why is ZK accelerating now? Sam points to a convergence of breakthroughs — cryptographic advances like Groth16 and SNARKs over the past five to seven years — paired with growing pressure in AI, Web3, and data governance to prove that computation happened as claimed.

“There’s this sense that regulators and technologists alike need new tools to govern computation at scale — and ZK gives us a way to create inviolable, checkable records of how computation happens.”

Looking forward, Sam sees usability and efficiency as the defining frontiers. In five years, he envisions a world where ZK proofs are as easy to integrate as an API call.

“ZK should feel like just another tool in the developer’s toolkit—with minimal overhead, but maximal impact.”