How can zero-knowledge proofs verify information without exposing it?

A zero-knowledge proof allows one party to demonstrate that a statement is true without revealing the underlying secret information beyond what the statement itself discloses.

For example, a suitably designed age-verification system could establish that a person meets an age threshold without revealing their full date of birth. This depends on trustworthy credentials and a correctly implemented proof system.

In a typical zero-knowledge proof, the prover demonstrates that they know information satisfying a particular condition, while the verifier checks the proof without receiving the underlying secret.

The technique does not make every part of the interaction private. Account details, network information or repeated use of a persistent identifier may still connect separate visits. A proof also cannot make an unreliable original claim trustworthy merely by hiding its contents.

The ICO’s guidance on zero-knowledge proofs explains their potential role in reducing disclosure.

For websites, the practical benefit is data minimization: verifying the specific fact needed for a service without routinely collecting all the information from which that fact can be established.