# google/longfellow-zk

Implementation of the Google Zero-Knowledge library for Identity Protocols.

Repository: https://github.com/google/longfellow-zk
Canonical: https://ross.abutalabs.com/products/longfellow-zk
Language: C++
License: Apache-2.0
License Family: permissive
Last push: 2026-09-03T00:05:31+00:00

## Health v2 (maintenance only)
Score: 75/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 100, release rhythm 65, longevity 35
- inputs: {"age_days": 491, "days_push": 0, "days_rel": 155, "gap_med": 38.0, "n_releases_24m": 7}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 1303, forks 123 (observed 2026-09-03T02:15:12.422016+00:00)

## What it is
A C++ library from Google implementing zero-knowledge proof protocols for identity verification, supporting standards like ISO MDOC, JWT, and W3C Verifiable Credentials. It enables anonymous credential construction from ECDSA signatures and is the reference implementation for an IETF draft specification.

## Use cases
- prove identity attributes without revealing personal data
- verify digital identity documents with zero-knowledge proofs
- build anonymous credentials from ECDSA signatures
- implement privacy-preserving age or citizenship verification
- integrate ZK proofs into MDOC or verifiable credential workflows
- evaluate zero-knowledge proof benchmarks in C++

## When to choose
- you need standards-based ZK proofs for identity documents like MDOC or verifiable credentials
- you want a Google-backed, actively developed C++ ZK library with an IETF draft specification
- you need anonymous credentials derived from ECDSA signatures

## When to avoid
- you need a general-purpose ZK-SNARK framework for arbitrary circuits
- your stack is not C++ or lacks bindings
- you require a library with completed, not in-progress, security reviews

## Facets
- artifact type: library
- maturity: active
- function: cryptography, security, auth, sdk
- domain: security, privacy, developer-tools
- platform: cpp, cross-platform
- tags: zero-knowledge-proofs, identity-verification, mdoc, verifiable-credentials, jwt, anonymous-credentials, ecdsa, privacy-preserving-authentication, identity, cryptography, linux, macos

## Member repositories
- google/longfellow-zk (main) score 75

## Provenance
- Observed fields: from GitHub, fetched 2026-09-03T02:15:12.422016+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-30T04:52:14.870365+00:00, confidence not recorded.
  - readme: https://github.com/google/longfellow-zk (fetched 2026-09-03T02:15:12.422016+00:00, sha 5d5fca0d6650)
- Data as of 2026-08-30T08:39:29.467469+00:00.