zkAttest

Polkadot-native DKIM/ZK Email attestations for People Chain evaluation.

zkAttest lets a user prove possession of a DKIM-signed email with a zero-knowledge proof, then verify that proof through Polkadot infrastructure. The project builds on upstream ZK Email circuits and adds the Polkadot-specific integration layer: PolkaVM verification, FRAME pallets, a governance-managed DKIM registry, Polkadot wallet UX, and a People Chain / DIM integration path.

Links:

• Demo site: https://msmrez.github.io/zkattest/
• Repository: https://github.com/msmrez/zkattest

What this is

zkAttest is a prototype credential source for Polkadot People / Project Individuality evaluation. It explores a DIM2-compatible email-ownership signal whose cryptographic trust path runs through:

1. the email provider's DKIM signature,
2. an on-chain DKIM key registry,
3. a Groth16 verifier compiled for PolkaVM / pallet-revive,
4. a FRAME pallet that handles proof verification, nullifiers, and attestation flow.

The current system demonstrates the core technical path:

• .eml parsing and DKIM metadata extraction in the browser demo,
• toy Groth16 browser proving and wallet-signed Asset Hub submission,
• a real zkEmail-derived circuit path through CLI / Node,
• proof verification against a deployed Asset Hub verifier,
• prototype FRAME pallets for DKIM registry and zkAttest logic.

zkAttest should first be evaluated as a supplemental DIM2-compatible credential source for Polkadot People / Individuality, not as a standalone proof-of-personhood mechanism.

What this is not

zkAttest is not positioned as a standalone unique-humanity system.

Email ownership is an attestation signal. It does not, by itself, establish that one account maps to one unique human. The intended first role is a supplemental DIM2-compatible credential signal for Polkadot People / Individuality evaluation, alongside stronger personhood mechanisms and policy decisions.

Current status

Component	State
Real zkEmail-derived Groth16 verifier on PolkaVM	Deployed and proof-verified on Polkadot Asset Hub mainnet
pallet-dkim-registry	Prototype complete, 5 source tests
pallet-zkattest	Prototype complete, 18 source tests: 5 pallet tests, 8 evm_abi tests, 5 ReviveVerifier tests
DKIM key scraper	Prototype that pulls real keys from Gmail, Outlook, Yahoo, ProtonMail, SendGrid
Prover SDK	TypeScript wrapper around @zk-email/helpers and snarkjs
Browser proof generation	Live toy-circuit Groth16 demo; real zkEmail-derived proof currently runs through CLI / Node
Browser on-chain submission	Wallet-signed revive.call to the deployed toy verifier
People Chain integration	Target path; production interface integration is grant work

Proof-critical package versions used in this repo:

Package	Version
@zk-email/helpers	6.4.2
@zk-email/circuits	6.3.4
snarkjs	0.7.6

Live mainnet artifacts for the current prototype:

Real zkEmail-derived circuit:

• Circuit: real-circuit/zkattest_email.circom
• Constraint count: approximately 315k
• Public inputs: 3
• Verifier contract: 0xca1a3ad129e204d9af942a30f7f09282d20e28bf
• Deploy tx: 0x271f59aa8c7670809efb8f76c594628cc0eeb8bc9f68f796ca8eff8a8fbf1edc
• Verify tx: 0x82bdae3a8530797f890d41d279daccc087d3a4e7e35ecaf2b99275cad4f71acc
• Recorded gas: refTime about 3.93e9, proofSize about 19.6 KiB

Toy circuit used by the browser demo:

• Circuit: web/circuit/circuit.circom
• Verifier contract: 0x4fa8678fb0188b29e49254759fb876eecdede468
• Verify tx: 0xe3e11b8a2b386e2aa77dd8168d7aac7200bb83529f44ad1d92e2922e061f76a8
• Recorded gas: refTime about 1.77e9, proofSize about 15.0 KiB

See artifacts/MANIFEST.md for checksums and artifact mapping.

Demo status: toy browser circuit vs real zkEmail circuit

The web demo has two separate purposes:

1. It parses .eml files locally and extracts DKIM metadata.
2. It runs a real Groth16 proof in the browser using a small toy circuit, then submits that proof to a toy verifier on Asset Hub.

The production email circuit is separate. The real zkEmail-derived circuit has been built and proof-verified through the CLI / Asset Hub path. Integrating full real-email proving into the browser is future work.

People Chain pallet integration is also future work. The current pallet is a prototype integration target, not a production People Chain deployment.

Live demo

• Demo site: https://msmrez.github.io/zkattest/
• Repository: https://github.com/msmrez/zkattest

The demo page is intentionally explicit about status: browser proving is a toy circuit, while the real zkEmail-derived proof path is currently CLI / Node plus Asset Hub verification.

Repository layout

pallets/
  dkim-registry/          On-chain registry of trusted (domain, selector) to DKIM pubkey
  zkattest/               Proof verification, nullifier, and People Chain integration target
prover/                   TypeScript prover helpers
scraper/                  DKIM key scraper prototype
real-circuit/             Real zkEmail-derived circuit build recipe and verifier artifacts
spike/                    Asset Hub deploy, proof generation, and verifier scripts
web/                      Static GitHub Pages demo
artifacts/MANIFEST.md     Checksums and artifact mapping
docs/REPRODUCIBILITY.md   Reviewer reproduction paths
docs/TRUST_MODEL.md       Trust assumptions and privacy notes
HOSTING.md                Cloudflare R2 upload notes

Reproducibility

See docs/REPRODUCIBILITY.md for the full reviewer checklist. Proof-critical dependency versions are pinned in the package files and summarized in the current status table above.

Real zkEmail path

Generate and locally verify a real zkEmail-derived Groth16 proof:

cd spike
npm install
curl -L https://pub-a34a2db2f64d4ca1b7914c0cfe6652fc.r2.dev/email_ownership/circuit_final.zkey -o circuit_final.zkey
node gen-proof.mjs

Expected signal:

• node gen-proof.mjs prints Local verify: OK.

Browser demo path

cd web
python3 -m http.server 8000

Open http://localhost:8000, drop a DKIM-signed .eml file, generate the toy Groth16 proof, and optionally connect a Polkadot wallet for the toy Asset Hub verification flow.

Asset Hub verifier path

Dry-run the real proof against the deployed Asset Hub verifier:

cd spike
DRYRUN_ONLY=1 CONTRACT=0xca1a3ad129e204d9af942a30f7f09282d20e28bf node verify-substrate.mjs

Expected signal:

• verify-substrate.mjs prints verifyProof returned: true.

Known limitations

These are scope boundaries for the current prototype:

• Email ownership is a credential signal, not complete proof of unique humanity.
• The browser demo uses a toy Groth16 circuit; the full zkEmail-derived browser prover is grant work.
• The real circuit currently uses minimal parameters and synthetic test inputs.
• The pallet-zkattest People Chain path is prototype-level until the target People interface is finalized and integrated.
• DKIM key rotation, registry governance, nullifier privacy, and replay prevention require production policy decisions.

See docs/KNOWN_LIMITATIONS.md for the full list and docs/TRUST_MODEL.md for the detailed trust model.

Security and trust assumptions

The current design relies on:

• DKIM provider DNS keys being available and correctly represented in the registry,
• governance-managed activation, expiry, and revocation of DKIM keys,
• upstream ZK Email circuit correctness,
• Groth16 trusted setup and artifact integrity,
• PolkaVM / BN254 precompile correctness,
• nullifier construction that prevents replay while preserving the intended privacy properties.

Roadmap / grant scope

Completed:

• Groth16 verifier compiled to PolkaVM via resolc 1.1.0.
• Real zkEmail-derived proof verified on Polkadot Asset Hub mainnet.
• FRAME prototype pallets with 23 source tests.
• Browser demo with DKIM parsing, toy Groth16 proof generation, and toy Asset Hub verifier submission.
• DKIM scraper prototype with real key pulls.
• Cloudflare R2 hosting for real-circuit .wasm, .zkey, and vkey artifacts.

Next:

• Reproducible build/devcontainer path.
• Production-oriented real email circuit parameters.
• Real zkEmail browser or hybrid prover path.
• pallet-zkattest integration against the production People interface.
• DIM2 attestation-source RFC / pre-proposal.
• Independent review of circuit, verifier, pallet, and registry assumptions.

License

Apache-2.0. See LICENSE.