dart_web3_bc_ur #

A pure Dart implementation of the Blockchain Uniform Resource (BC-UR) standard. It enables efficient, segmented, and secure data transmission via QR codes, specifically designed for air-gapped hardware wallets.

🚀 Features #

• Fountain Codes (UR): Robust data segmentation using Luby Transform (LT) codes for large transaction payloads.
• Type Registry: Support for standardized UR types including crypto-multi-accounts, eth-signature, and psbt.
• Cbor Logic: Built-in CBOR encoding/decoding compliant with the UR specification.
• Hardware Agnostic: Fully compatible with Keystone, Foundation, SeedSigner, and BlueWallet implementations.

Usage Flow #

sequenceDiagram
    participant B as Raw Bytes
    participant C as CBOR Encoder
    participant F as Fountain Encoder
    participant Q as QR Display
    B->>C: encode()
    C->>F: build frames
    F->>Q: animation cycle
    Note over Q: ur:eth-tx/1-5/...
    Note over Q: ur:eth-tx/2-5/...

🏗️ Architecture #

graph LR
    Bytes[Binary Data] --> CBOR[CBOR Encoding]
    CBOR --> UR[UR Data Structure]
    UR --> Fountain[Fountain Multi-part Encoding]
    Fountain --> QR[QR Frame Generator]
    
    style QR fill:#fff,stroke:#333,stroke-width:2px;

📚 Technical Reference #

Core Classes #

🛡️ Security Considerations #

• Visual Data Transfer: Air-gapped communication via QR codes provides a physical barrier against remote exploits.
• Segment Integrity: The UR protocol includes checksums for every frame; the decoder ensures 100% data integrity before reconstruction.
• Data Leakage: Although QR-based, ensure sensitive data is not scanned in environments where unauthorized cameras might be recording.

💻 Usage #

Generating Multiple QR Frames #

import 'package:dart_web3_bc_ur/dart_web3_bc_ur.dart';

void main() {
  final payload = Uint8List.fromList([0xDE, 0xAD, 0xBE, 0xEF]);
  final ur = UR.encode(payload, type: URTypes.ethTx);

  final encoder = UREncoder(ur, maxPartSize: 200);
  
  // Get the next QR part to display
  while (!encoder.isComplete) {
     final frame = encoder.nextPart();
     print('Display QR: $frame');
  }
}

📦 Installation #

dependencies:
  dart_web3_bc_ur: ^0.1.0