OpenAC Example App

Sample iOS app that runs the OpenAC zero-knowledge pipeline for Taiwan's MOICA digital identity: authenticate with the MOICA app, generate ZK proofs for the cert chain (RS4096) and device signature (RS2048) circuits, then submit them to a server for link verification. It uses OpenACSwift—Swift bindings for OpenAC on iOS.

Demo

Download Circuits	Sign with MOICA	Generate Proof
~10 seconds	~11 seconds	prove ~5 s | verify ~13 s

How it works

The app walks through four stages:

1. Setup — Download Circuit files

Downloads three files from cloud storage (shown only when not yet present):

File	Source	Size
cert_chain_rs4096_proving.key	zkID releases (gz)	~large
device_sig_rs2048_proving.key	zkID releases (gz)	~large
g3-tree-snapshot.json.gz	moica-revocation-smt releases	—

2. TW FidO / MOICA — Authenticate with national ID

Step	Description
ID Number	Enter your Taiwan national ID (e.g. A123456789)
TBS	To-be-signed challenge bytes. Tap the refresh button to call POST /challenge on the server and receive a challenge_bytes.
Get SP Ticket	Calls POST /fido/sp-ticket with the ID number and TBS. Returns a signed sp_ticket.
Verify with MOICA	Deep-links to mobilemoica://moica.moi.gov.tw/a2a/verifySign so the MOICA app performs the signature. Returns to openac://callback.
Auth Result	Calls POST /fido/ath-result, polling until the signed response and signer certificate are available.
Generate Input	Calls generateCertChainRs4096Input from OpenACSwift to build the circuit input JSON from the MOICA response, issuer certificate, TBS, and SMT snapshot.

3. Pipeline — ZK proof

Step	Description
Generate Proof	Runs proveCertChainRs4096 and proveDeviceSigRs2048 (Groth16 provers). Reports time in ms.
Verify	Submits proofs to POST /link-verify with the challenge ID, cert chain type (rs4096).

Individual steps can be triggered with their own play button, or tap Run All Steps in the toolbar to run prove + verify in sequence.

Link-verify request format

{
  "cert_chain_type": "rs4096",
  "cert_chain_proof": "<base64-encoded bytes>",
  "device_sig_proof": "<base64-encoded bytes>",
}

Requirements

• iOS 16+
• Xcode 15+
• MOICA app installed on device for the authentication flow
• A running server exposing /challenge and /link-verify endpoints

Dependencies

• OpenACSwift — Swift bindings for proveCertChainRs4096, proveDeviceSigRs2048, verifyCertChainRs4096, verifyDeviceSigRs2048, generateCertChainRs4096Input, linkVerify
• CryptoKit (system) — AES-256-GCM for the sp_checksum required by the TW FidO API
• zlib (system) — decompresses .gz key files on-device

Running the project

1. Open OpenACExampleApp.xcodeproj in Xcode.
2. Select an iPhone simulator or device.
3. Build and run.
4. On first launch, tap Download Circuit in the Setup section and wait for all three files to download.
5. Tap the refresh button next to TBS to fetch a challenge from the server.
6. Enter your ID number, then follow the TW FidO / MOICA steps in order.
7. Tap Run All Steps (or individual play buttons) to generate and verify the ZK proofs.

See also

• OpenACSwift — API, installation, and prebuilt binaries
• zkID releases — circuit and key files
• moica-revocation-smt — SMT snapshot releases