OpenAC Example App

Sample iOS app that runs the OpenAC zero-knowledge pipeline for the FIDO/SHA256RSA4096 circuit: authenticate with Taiwan's MOICA digital signature service, generate a ZK proof, and verify it on-device. It uses OpenACSwift—Swift bindings for OpenAC on iOS.

Demo

Download Circuits	Sign with MOICA	Generate Proof
~19 seconds	~11 seconds	prove ~ 9 seconds | verify ~9 seconds

How it works

The app walks through four stages:

1. Setup — Download Circuit files

Downloads sha256rsa4096.r1cs (~92.9 MB) and rs256_4096_proving.key (~66.9 MB) from cloud storage. The verifying key is fetched on demand when Verify is first run. Once downloaded, the Setup section collapses.

2. FIDO / MOICA — Authenticate with national ID

Step	Description
ID Number	Enter your Taiwan national ID (e.g. A123456789)
Get SP Ticket	Calls POST /moise/sp/getSpTicket on fidoapi.moi.gov.tw with an AES-256-GCM checksum. 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 with rtn_val.
Auth Result	Calls POST /moise/sp/getAthOrSignResult, polling every 4 s until the signature is available. Retrieves signed_response and the signer's certificate.
Generate Input	Calls generateInputFido from OpenACSwift to build input.json from the MOICA response, ready for the ZK circuit.

3. Pipeline — ZK proof

Step	Description
Generate Proof	Calls proveFido — runs the Groth16 prover over the FIDO circuit. Reports proof size and time.
Verify	Calls verifyFido — verifies the Groth16 proof on-device.

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

Requirements

• iOS 16+
• Xcode 15+
• MOICA app installed on device for the FIDO authentication flow
• A registered FIDO service ID and matching AES key (see Secrets)

Dependencies

• OpenACSwift — Swift bindings for proveFido, verifyFido, setupKeysFido, generateInputFido
• ZIPFoundation — extracts downloaded .zip circuit archives
• CryptoKit (system) — AES-256-GCM for the sp_checksum required by the FIDO API

Secrets

The FIDO API requires a service ID and AES key. Create OpenACExampleApp/Secrets.swift (gitignored):

enum Secrets {
    static let fidoSpServiceID = "<your-sp-service-id>"
    static let fidoAESKey      = "<your-aes-key-base64>"
}

Both values can also be injected via environment variables FIDO_SP_SERVICE_ID and FIDO_AES_KEY (useful for CI).

Running the project

1. Open OpenACExampleApp.xcodeproj in Xcode.
2. Add your Secrets.swift (see above).
3. Select an iPhone simulator or device.
4. Build and run.
5. On first launch, tap Download Circuit in the Setup section and wait for the download to complete (~160 MB total).
6. Enter your ID number, then follow the FIDO / MOICA steps in order.
7. Tap Run All Steps (or individual play buttons) to generate and verify the ZK proof.

See also

• OpenACSwift — API, installation, and prebuilt binaries
• zkID releases — circuit and key files