OpenAC Android Example

An Android example app demonstrating zero-knowledge proof generation and verification using OpenACKotlin.

Demo

Download Circuit	FIDO Signature
~ 19 seconds	~8 seconds

Generate Proof	Verify Proof
~ 21 seconds	~ 20 seconds

Overview

This app uses OpenACKotlin to run the FIDO zkID circuit on Android. The single zkID tab exposes a scrollable screen with four cards that unlock sequentially:

Circuit Download Card

Always visible. Shows a progress bar with the current file name and live percentage while fetching. The MOICA and ZK Pipeline cards are hidden until both the circuit and proving key are ready.

• Download Circuit + Keys — fetches and unzips sha256rsa4096.r1cs (circuit) and rs256_4096_proving.key (proving key) sequentially from their CDNs; shows download and unzip timings on completion

MOICA Signature Card (visible after circuit + keys are ready)

Enter a masked ID Number, then follow the three numbered steps:

• 1. Get SP Ticket — calls getSpTicket and displays the result
• 2. Open MOICA App — launches the MOICA app via deep-link for the user to sign (app-to-app flow); enabled after an SP ticket is obtained
• 3. Poll ATH Result — calls getAthOrSignResult and displays the signed response and cert snippets; enabled after an SP ticket is obtained

fido_input.json Card (visible after Generate Input completes)

Expandable card showing the generated circuit input JSON, with a copy-to-clipboard button.

ZK Pipeline Card (visible after circuit + keys are ready)

• 4. Generate Input — calls generateInputFido to produce fido_input.json from the ATH result; enabled after ATH polling succeeds
• 5. Generate Proof — calls proveFido and reports proof time (ms) and proof size (bytes)
• 6. Verify Proof — calls verifyFido to confirm the proof is valid; downloads the verifying key on demand if not present; enabled after prove succeeds
• Run All (Prove → Verify) — convenience button that runs steps 5–6 in sequence (Generate Input must be run separately first)

Getting Started

Clone the repo and open it in Android Studio.

git clone https://github.com/zkmopro/OpenACAndroidExample

Configuration — Secrets.kt

The app requires FIDO SP service credentials. Create or update the file below before building (it is git-ignored):

app/src/main/java/com/example/openacandroidexample/Secrets.kt

package com.example.openacandroidexample

object Secrets {
    const val fidoSpServiceID: String = "your-sp-service-id"
    const val fidoAESKey: String = "your-32-byte-aes-key-base64"
}

Constant	Description
fidoSpServiceID	SP service ID issued by MOICA
fidoAESKey	32-byte AES-256 key (base64-encoded) used to compute sp_checksum via AES-256-GCM

Credentials can also be supplied at test time via environment variables FIDO_SP_SERVICE_ID and FIDO_AES_KEY; the app falls back to Secrets.kt if those are absent.

The app requires an internet connection on first launch to download the circuit file from the CDN.

Architecture

File	Description
MainActivity.kt	Entry point; wires the MOICA app2app callback URI into the ViewModel
ProofViewModel.kt	All state and business logic — download, MOICA API calls, ZK pipeline
ZkIdComponent.kt	Compose UI — circuit download card, MOICA signature card, fido_input.json viewer card, ZK pipeline card
FidoApi.kt	MOICA FIDO REST API client (getSpTicket, getAthOrSignResult, pollSignResult, computeSpChecksum)
Secrets.kt	Fallback SP service credentials (git-ignored)

Dependencies

• OpenACKotlin — Kotlin bindings for the mopro ZK proving backend (generateInputFido, proveFido, verifyFido)