Models change. Proofs remain.

Lemma API —
the ZK proof issuance API.

Issue provenance, authentication, authority, inference, and attribute proofs from one API. Verification is always free.

Standards: MCP / A2A / x402 / C2PA / W3C VC

Try the Sandbox (testnet · free) Read the specs →
Why Lemma API

Five kinds of proof, one API.

Five proof classes in one integration

Issue provenance, authentication, authority, inference, and attribute proofs from the same API.

Verification is always free, independently checkable

Anyone, anywhere can verify your proofs at no cost — checked by a third party.

x402-native, non-custodial

Payments settle over x402. You never hand over keys — you only prove the authority (self-custody).

suites

Five proof suites.

Each suite's concept and issuance steps live on its canonical page. This is the index — rates and plans are consolidated on the pricing page.

  • Provenance Prove origin without handing over the original.
    Learn more →
  • Authentication Prove identity without sending a key.
    Learn more →
  • Authority Delegate authority without handing over a key.
    Learn more →
  • Inference Prove inference without disclosing the model.
    Learn more →
  • Attribute Prove you meet a requirement without revealing the attribute.
    Learn more →

Rates and plans are consolidated on the pricing page. See pricing →

How you integrate

From key to verification.

  1. 01 Mint a key in the Dashboard
  2. 02 Issue a proof (per-issuance via x402, or a monthly allowance)
  3. 03 Verification is free — anyone, anywhere

One middleware layer in your existing flow; it rides the standards you already use (MCP · x402 · A2A). Endpoints and code live in the specs. This page never calls the API.

Billing model

Issuance is billed; verification is free.

  1. You pay only when a proof is issued. Anyone verifying it pays nothing — anywhere, anytime.
  2. Usage-based (settled per issuance via x402) plus a monthly quota / grade (dashboard subscription).
  3. On-chain provenance is optional — usage-based defaults to off-chain; monthly plans include permanence as standard.
Coming soon

Production billing is coming soon — start free on the testnet Sandbox and issue proofs there.

How it fits

The authentication suite is the Lemma API. Trust402 is the self-serve face.

  • The authentication suite is part of the Lemma API (/seal is its landing page).
  • Trust402 is the self-serve surface for the suites (Pay / Sell).
Get started

Issue your first proof.

For developers
Try the Sandbox (testnet · free) Specs GitHub →
For enterprises
Book a Discovery Call