Google open-sources its Zero-Knowledge Proof libraries for private age checks

Google has released its Zero-Knowledge Proof (ZKP) cryptographic libraries under an open-source license, publishing the code as ‘longfellow-zk’ on GitHub. The move follows a commitment tied to its partnership with German banking group Sparkasse on EU age-assurance efforts. ZKP lets someone prove a single claim about themselves — such as being over 18 — to a website or service without disclosing any other personal data, sidestepping the usual tradeoff between age verification and mass data collection.

The timing is aimed squarely at Europe’s regulatory calendar. The EU’s eIDAS Regulation, taking effect in 2026, pushes Member States to fold privacy-preserving techniques like ZKP into the forthcoming European Digital Identity (EUDI) Wallet. By making a performant implementation freely available, Google is positioning its code as a ready building block that governments and vendors can drop into wallet projects rather than developing equivalent cryptography from scratch.

The significance is less about novel math than about lowering the barrier to deployment. Efficient, production-grade ZKP implementations have been scarce outside specialized research and blockchain circles, so an openly licensed, general-purpose library could accelerate privacy-focused digital ID and age-gating tools across both public and private sectors. It also gives cryptography researchers a concrete codebase to scrutinize and extend — though real-world trust will depend on independent review of the implementation.