What are zero-knowledge proofs?

A zero-knowledge proof is a cryptographic method that lets one party, the prover, convince another party, the verifier, that a statement is true without revealing anything beyond the fact that it is true. ethereum.org gives the example of proving you are a citizen without showing your passport details. In crypto, zk proofs have become a core tool for both scaling and privacy.

How does a zero-knowledge proof work?

The concept was introduced in a 1985 paper by Shafi Goldwasser, Silvio Micali and Charles Rackoff on interactive proof systems. In the original setup, the prover and verifier exchange messages. The verifier asks challenges, and the prover can only answer all of them correctly if the statement really is true. After enough rounds, the verifier is convinced, yet has learned nothing else.

A simple everyday comparison is proving you know a password without typing it out. The verifier ends up confident you know it, but never sees it. Modern blockchain systems mostly use non-interactive proofs, where the prover produces a single proof that anyone can check later without a back and forth conversation. This builds on the same math covered in how cryptography secures crypto.

What is the difference between a zk-SNARK and a zk-STARK?

These are the two best known families of proof systems used in crypto.

A zk-SNARK (zero-knowledge succinct non-interactive argument of knowledge) produces small proofs that are quick to verify. Many SNARKs need a "trusted setup," a ceremony where participants generate shared parameters and must destroy their secret inputs. The setup stays secure as long as at least one participant was honest. SNARKs rely on elliptic curve cryptography, which ethereum.org notes is believed to be vulnerable to future quantum computers.

A zk-STARK (zero-knowledge scalable transparent argument of knowledge) needs no trusted setup and is considered resistant to quantum attacks. The trade-off is larger proofs, which cost more to verify on Ethereum.

How are zero-knowledge proofs used in crypto?

The biggest use today is scaling. A zk-rollup runs transactions off Ethereum and posts a validity proof showing the new state was computed correctly, so Ethereum does not need to re-run every transaction. ethereum.org stresses that this alone is not a privacy feature, since rollup transaction data is still published.

Privacy is the other big area. ethereum.org describes tools that let people prove they are over 18 without sharing a birth date, cast secret ballots, or show that funds came from an approved group of sources. For networks built mainly around hiding payment details, see what is a privacy coin.

Will Ethereum itself use zk proofs?

Researchers are working on a zkEVM for verifying Ethereum's own blocks. As of October 2026, ethereum.org describes this as active research that is not yet part of production clients. The main hurdle is speed, since proving a block can still take minutes to hours while new blocks arrive every 12 seconds.