openac-sdk

ZK proof SDK for SD-JWT credentials. Prove predicates (age >= 18, balance <= credit_limit, etc.) without revealing claim values. Built on Spartan2 + Hyrax over secp256r1.

Install

npm install openac-sdk

Node 18+. Browser usage requires preloading WASM and passing wasmModule to OpenAC.init.

Quickstart

import { OpenAC } from "openac-sdk";

const openac = await OpenAC.init();
const keys = await openac.loadKeysFromUrl("1k");

const predicate = {
  claim: "roc_birthday",
  op: "<=" as const,
  value: new Date("2008-01-01"),
};

// Precompute once per credential. Pass the predicate so format inference works.
const precomputed = await openac.precompute({
  jwt: sdJwtToken,
  disclosures: ["WyJzYWx0...", "..."],
  issuerPublicKey: { kty: "EC", crv: "P-256", x: "...", y: "..." },
  keys,
  predicates: predicate,
});

// Present per verifier session.
const proof = await openac.present({
  precomputed,
  verifierNonce: "challenge-123",
  devicePrivateKey: "0xabcdef...",
  keys,
  predicates: predicate,
});

const result = await openac.verify(proof, keys.verifyingKeys());
console.log(result.valid, result.expressionResult);

Predicates

// Literal comparison
{ claim: "age", op: ">=", value: 18 }

// Date (auto-encoded to ROC date format)
{ claim: "roc_birthday", op: "<=", value: new Date("2008-01-01") }

// Claim-to-claim
{ claim: "balance", op: "<=", compareTo: { claim: "credit_limit" } }

// Nested boolean composition
{
  all: [
    { claim: "age", op: ">=", value: 18 },
    {
      any: [
        { claim: "kyc_tier", op: "==", value: 2 },
        { claim: "kyc_tier", op: "==", value: 3 },
      ],
    },
  ],
}

Operators: "<=", ">=", "==" Value types: bigint, number, Date, string Combinators: all, any, not (nest arbitrarily) Format: inferred from value type (Date becomes date, numeric becomes uint, string becomes string). Override with format: "date" | "uint" | "string" on any predicate.

Verifier

A verifier only needs the two verifying keys, not the proving keys.

import { OpenAC } from "openac-sdk";

const openac = await OpenAC.init();

const result = await openac.verify(proof, {
  prepareVerifyingKey, // Uint8Array
  showVerifyingKey,    // Uint8Array
});
// result.valid            both proofs verified and shared commitment matches
// result.expressionResult  boolean output of the predicate expression
// result.deviceKey         always null; binding flows through comm_W_shared

The verifier check includes byte-equality of comm_W_shared between the Prepare and Show instances before either SNARK is verified. This is the load-bearing security check that ties the two proofs to the same underlying credential.

Configuration

const openac = await OpenAC.init({
  keysBaseUrl: "https://my-cdn.example/keys", // override the default R2 endpoint
  assetsDir: "./assets",                       // override circuit-WASM asset path
  wasmModule: preloadedWasm,                   // browser: pre-init WASM and pass it
});

Testing helpers

import { generateDummyCredential } from "openac-sdk/testing";

const cred = generateDummyCredential({
  size: "1k",
  claims: [
    { key: "roc_birthday", value: "0900101" },
    { key: "roc_max", value: "0950101" },
  ],
});
// cred.jwt, cred.disclosures, cred.issuerPublicKey, cred.devicePrivateKeyHex

Deterministic keys; JWT is sized to fit the chosen circuit slot.

API

| Method | Returns | |---|---| | OpenAC.init(config?) | Promise<OpenAC> | | openac.loadKeysFromUrl(size, url?) | Promise<KeySet> | | openac.loadKeys(serialized) | Promise<KeySet> | | openac.precompute(req) | Promise<PrecomputedCredential> | | openac.present(req) | Promise<PresentationProof> | | openac.verify(proof, vks) | Promise<VerificationResult> | | openac.verifyProof(serialized, vks) | Promise<VerificationResult> |

size is "1k" | "2k" | "4k" | "8k". precompute auto-picks the smallest size that fits the JWT.

Build

npm install
npm run build:all   # WASM (needs Rust + wasm-pack) + TypeScript
npm test

Dependencies

@noble/curves and @noble/hashes. The SDK loads circuit assets and the WASM module from disk via Node's fs/path/url builtins, so Node 18+ is required for the default initialization path.

License

MIT