zkSNARK

A zkSNARK is a method from cryptography — the science of secure encryption and proof. It allows you to prove to someone that a statement is true without revealing any of the underlying details. That sounds paradoxical, but it isn’t. Consider this example: you want to prove that you know the password to an account — without stating the password itself. That is exactly what a zkSNARK achieves. The name stands for “Zero-Knowledge Succinct Non-Interactive Argument of Knowledge,” which roughly translates to: a concise, non-interactive proof of knowledge without disclosing information.

Why proofs without data disclosure are so valuable

In digital systems, you constantly have to prove who you are or what you know. Normally, that means: sharing data. The bank checks your salary by having you show your bank statement. A website checks your age by having you upload your ID. With a zkSNARK, only the proof would be transmitted instead — no ID, no bank statement, no number.

This is not just a privacy advantage. It is also a security advantage. Data that is never transmitted cannot be stolen either. For systems that work with very large numbers of users — such as payment services or voting platforms — this is a fundamental difference.

How a zkSNARK generates a proof

The core of the method works as follows: A computation — for example, “I have sufficient funds for this payment” — is translated into a mathematical formula. The prover, meaning the person who wants to prove something, runs this formula using their secret data and in doing so generates a tiny data set: the proof. This proof is typically only a few hundred bytes in size, regardless of how complex the original computation was.

The verifier — the other party — only receives this proof. They can check within milliseconds whether it is valid, without ever having seen the original data. This is the core of the name: “succinct” means brief, “non-interactive” means that no back-and-forth is needed — a single data set is enough.

Important: the method requires a one-time setup step, the so-called “trusted setup.” During this step, mathematical parameters are established that apply to all subsequent proofs. This step is delicate: anyone who knows the random numbers generated during it could create forged proofs. Many projects therefore carry out the setup with dozens of participants, so that no single person alone knows the critical data.

zkSNARKs in blockchains and digital identities

zkSNARKs are best known in connection with cryptocurrencies. The currency Zcash was one of the first to use the method in 2016: transactions are stored fully encrypted on the blockchain, yet remain verifiably valid — thanks to zkSNARK proofs. Ethereum also uses the principle: so-called layer-2 networks like zkSync or Polygon zkEVM bundle many transactions, prove their correctness with a single zkSNARK, and send only this one proof to the main chain.

Outside of cryptocurrencies, zkSNARKs are increasingly being discussed for digital identities. The EU initiative for a digital wallet — the so-called EUDI Wallet — is examining how citizens can prove their age or nationality without disclosing more data than necessary. zkSNARKs are a serious candidate for this.

In the tech press, the term frequently appears in connection with “Zero-Knowledge Rollups,” or ZK-Rollups for short. Anyone who encounters this buzzword will almost always come across zkSNARKs or the related method zkSTARK — which does without the delicate trusted setup, but produces larger proofs in return.