Bringing Zero Knowledge Proofs to the Masses

The arcane world of cryptographic proofs seldom finds expression on the dashboard of your average automobile, but a partnership between Galois and Cybernetica is steering the state of the art in privacy-preserving technology towards the road less traveled—in Estonia, to be precise.

In 2020, Estonia’s Environmental Investment Centre introduced a public program to encourage the purchase of electric vehicles (EVs), part of a larger effort to ease the country’s green transition. In the scheme, citizens who purchased a fully electric vehicle were eligible for a €5,000 pre-tax subsidy if they drove their EV at least 80,000 kilometers within four years, at least 80 percent of which was within Estonian borders. Proving compliance, however, demands an insidious choice: surrendering personal travel history data or forsaking the subsidy.

“The standard approach for tracking something like this is to stick a device in your car that reports where you’re driving,” explained Galois Principal Researcher Alex Malozemoff. “That raises obvious privacy concerns.”

These sorts of private-data-for-financial-benefit trades are familiar to those who have grappled with American car insurance mongers, who frequently offer “usage-based” rates (i.e., the chance for a discount, contingent on good driving behavior) in exchange for permission to gather detailed data about your driving habits, including speed, acceleration and braking patterns, mileage, and time of day. Giving up this sort of information can open consumers to financial profiling, loss of control over where and how their data is shared, and even personal security risks. For example, it’s been known for over 10 years that four samples of time and location are enough to uniquely identify 95% of individuals. Personal data has become a kind of currency, traded for tangible or intangible benefits—many of which are needed to function in modern society—but with few protections available for individuals caught in the crossfire. 

Now, in a vivid illustration of technology meeting the challenges of public policy, Galois and Cybernetica have partnered to inject a dose of privacy into these sorts of transactions. Our novel approach involves using Zero-Knowledge Proofs (ZKPs) to allow Estonian EV drivers to confirm eligibility for subsidies without laying bare their travel patterns. The proof is conclusive, the data is cryptographically protected, and the roads retain their secrets.

Under the Hood: Zero-Knowledge Proofs

A Zero Knowledge Proof—the approach around which this whole technology hinges—is a cryptographic technique that allows an individual (or computer system), called the “Prover,” to prove to another individual (or computer system), called the “Verifier,” that a statement is true without revealing the statement’s actual content.

Picture a simple analogy: a colorblind person (the Verifier) holds two differently colored balls, and an observer (the Prover) wants to convince them that the colors differ. To prove that claim, the observer instructs the colorblind person to hide the balls behind their back and potentially swap them from one hand to the other. When the balls are revealed again, the observer correctly identifies whether the balls were swapped. By repeating this process, with the observer consistently identifying swaps over dozens of trials, the statistical improbability of guessing correctly convinces the Verifier of the claim that the balls are, in fact, different colors. Thus, even though the colorblind person does not have data about the balls’ individual colors, the observer can prove a relevant fact about them. ZKPs work in a similar manner, strengthening privacy in digital transactions by allowing one party to verify the truth of a statement to another, without sharing any underlying data along the way.

“In our case, you can prove in zero knowledge whether or not your car has passed a kilometer and location threshold,” explained Malozemoff. “All they would learn is ‘yea,’ or ‘nay’—only the information they need to confirm whether you qualify for the EV subsidy.”  

A Road Map to Ubiquity

Just as importantly, Galois and Cybernetica built their application to be usable by normal people via a web browser.

“One big reason zero-knowledge proofs aren’t more commonly used is the level of expertise needed,” Malozemoff explained. “The best technologies are the ones that are hidden behind the scenes. Think of secure browsing: You never have to think about it; it just works. In our application, the user doesn’t even have to know that zero-knowledge proofs are happening under the hood. They just open up their browser, go to the webpage, upload their telemetry data, and it executes the proof.”

The actual zero-knowledge backend used in this project is not new—it’s a tried and true Galois technology that already existed and has been used successfully for other applications. What is new, and exciting, about this project is that it takes a sophisticated technology and makes it accessible and actionable for end users, without requiring them to understand (or even notice) what’s happening behind the curtain. By making ZKP technology—previously usable only by an elite priesthood of cryptographic experts—widely usable in a frictionless web format, Galois has opened the floodgates of possibility across industries and applications. 

Health insurers may soon be able to verify the absence of pre-existing conditions without ogling medical charts. Banking portals could affirm a loan applicant’s financial probity without an intrusive peep into their transaction history. Background checkers could confirm whether a job applicant meets standards without accessing the details of their entire history. In each instance, ZKP’s promise is a secure exchange with minimal exposure—a profound boon in our data-drenched age.

Our vision for the future of technology is one where privacy, security, and ease-of-use go hand in hand. And with the successful implementation of ZKPs in automotive data, we’re just getting started. At Galois, we’re excited to drive this vision forward and continue exploring the myriad ways ZKPs can be a game-changer for privacy in the digital age.