The business case for smart contracts is building fast. Major financial institutions are using programmable, code-based agreements to underpin financial workflows, supply chain operations, and tokenization initiatives. Developers are being asked to prove the value.
But there’s a problem most organizations don’t fully see until they’re already stuck: privacy.
Public blockchains are transparent by design. Every transaction is visible. That’s the feature that makes them trustworthy—and the reason enterprises can’t simply deploy business logic on one without first addressing confidentiality. If your competitors can see your contract terms, you don’t have a business case. You have a liability.
“B2B transactions operate with a degree of confidentiality,” says Clare Adelgren, EY Global Blockchain Leader. “If businesses are going to transact on a public blockchain, they need privacy—but they need privacy in a very distinct flavor.”
The flavor she’s describing is zero-knowledge cryptography. It’s a technique that lets one party prove a statement is true without revealing the underlying data. In a smart contract context, it means you can execute and verify business logic on a public chain without exposing your commercial terms to anyone who shouldn’t see them.
The problem is that zero-knowledge proofs are hard. Not hard, the way learning Solidity is hard — PhD-level mathematics hard.
The Skill Set Doesn’t Exist in Most Teams
“You need both in the room,” Adelgren says, referring to blockchain developers and cryptographers. “Those people, that talent, aren’t always available.” The typical enterprise engineering team—even a strong one—doesn’t include zero-knowledge specialists. And without them, building privacy-preserving smart contracts from scratch takes weeks. That’s assuming developers already know their way around Solidity and public blockchain infrastructure. Most don’t start from that baseline either.
The deeper issue is that you can’t build a business case without a proof of concept. And you can’t build a proof of concept if the privacy layer requires expertise your team doesn’t have. That’s the bottleneck: not interest, not tooling budget, not blockchain fundamentals. It’s a ceiling of cryptography skills that stops experimentation before it starts.
EY has been working on this problem for 10 years. The firm started investing in blockchain privacy research during the early days of crypto, with a dedicated R&D team of PhD mathematicians based in London. The result is two open-source tools now in the public domain: Nightfall, a zero-knowledge rollup for private token transfers on Ethereum, and Starlight, a ZK proof compiler that converts standard Solidity smart contracts into privacy-preserving applications.
Both are technically available to any developer who wants them. But “available” and “accessible” are different things.
“The coding is there for Starlight, but it’s very complex,” Adelgren says. “You need to understand it, integrate it into your flow, set up the environments, and run the proofing systems. That would probably take several weeks—depending on the complexity of your contract.”
The Sandbox Removes the Setup
In March 2026, EY launched the EY Blockchain Privacy Sandbox: a web-based environment that puts Starlight’s capabilities in front of developers without the configuration overhead. No local installation. No environment setup. Developers bring an existing Solidity contract, annotate the fields they want to keep private, and run the transpiler. Outcomes: a privacy-enabled version of the contract, with API endpoints included and ready for integration.
“You suddenly don’t need to worry too much about the complexity of the math that sits behind the zero knowledge,” Adelgren says. “You can play in the sandbox, see how it’s working, and start building your business case.”
The result is a working proof of concept in under an hour. That matters because the POC is the point. This isn’t a production environment—it’s a validation tool. The goal is to let teams quickly understand what privacy-preserving smart contracts actually look like before committing engineering resources to a deeper build. What’s visible, what’s hidden, how the logic behaves, where the access controls live—those questions get answered in the sandbox before they become expensive to answer later.
Interest in ZK technology is accelerating. The global zero-knowledge proof market was estimated at roughly $1.3 billion in 2024 and is projected to reach approximately $7.6 billion by 2033, growing at a 22.1% compound annual growth rate, according to Grand View Research. The banking and financial services sector accounts for the largest share of that demand, which tracks with where enterprise smart contract interest is concentrated right now.
Where the Real Use Cases Are
Tokenization is the most mature entry point. Adelgren says EY already has clients doing it, and the tooling to support it is ready. Supply chain and financial workflow use cases are further out, partly because the transaction volume requirements are more demanding, and scalability in privacy-preserving systems is still developing.
She’s candid about it: “We’re still in the early days.” EY’s Nightfall technology can process blocks of transactions in anywhere from 6 to 20 minutes—workable for some use cases, not all. The path forward involves parallel processing and componentized infrastructure designed to scale as the architecture matures. Cost per transaction has already fallen significantly over the past five years, and she expects that trend to continue.
For engineering leaders who want to start experimenting, Adelgren’s advice is straightforward: don’t wait for a blockchain specialist. Get experienced full-stack developers familiar with Solidity—AI coding tools can help close that gap quickly. For the zero-knowledge layer, use tooling like the Privacy Sandbox to run experiments rather than building from scratch.
The broader shift is worth paying attention to. About 12 months ago, something changed in the blockchain landscape. Crypto remains, but a more foundational layer is emerging: blockchain as a trust infrastructure for financial systems. Stablecoin adoption, tokenization, and programmable finance are advancing faster than most engineering teams realize.
“Don’t lose sight of what some of these big transformational changes are that are happening in the environment around you,” Adelgren says. “The job of a developer is changing a lot at the moment. And it’s super exciting.”
Developers who want to explore the sandbox can access it at blockchain.ey.com.
