Offline Bitcoin Block Verifier

A single-file Progressive Web App (PWA) for verifying Bitcoin blocks entirely offline. Download blocks while online, then verify their integrity without any network connection.

Features

• Block Verification — Verifies transaction hashes, Merkle root, and block header hash
• Transaction Viewer — Browse transactions in a block, filter by address
• Block Download — Fetch blocks from public Bitcoin RPC endpoints
• Hash File Management — Maintain a local list of known block hashes for cross-verification
• Built-in File Manager — OPFS-based storage; import, export, and manage files without leaving the app
• Fully Offline — Service worker caches the app for offline use
• Installable — PWA manifest allows install on desktop and mobile

How It Works

1. Import or download block data using the File Manager or Download Block section
2. Load a hash file (optional) containing known block hashes for extra verification
3. Check a block — the app independently verifies:
   • Each transaction's serialized hash matches its txid
   • The Merkle root computed from all txids matches the block header
   • The double-SHA256 of the 80-byte header matches the block hash
   • The block hash matches your stored hash file (if loaded)

All cryptography uses the browser's native crypto.subtle API — no external libraries.

File Structure

oflibit_aio.html   — The entire application (HTML + CSS + JS)
service-worker.js  — Caches the app for offline use
manifest.json      — PWA manifest
favicon.ico        — App icon
icon-192.png       — PWA icon (192x192)
icon-512.png       — PWA icon (512x512)
data/              — Sample block JSON files and hash list for testing

Usage

Serve the files from any static web server (or open locally with a server for service worker support):

# Python
python -m http.server 8000

# Node
npx serve .

Then open http://localhost:8000/oflibit_aio.html in a modern browser.

File Manager

The File Manager uses the browser's Origin Private File System (OPFS) to store files persistently. Files are organized into three categories:

Category	Purpose
Hashes	Block hash list files (.txt, format: height: hash)
Blocks	Downloaded block JSON files
Verify	Block files imported specifically for verification

Import files from your device here, then use them in the other sections via the dropdown selectors.

RPC Endpoints

The app ships with several public Bitcoin RPC endpoints pre-configured. You can also enter a custom endpoint (e.g., your own Bitcoin Core node).

Browser Requirements

• Modern browser with crypto.subtle support (all current browsers)
• OPFS support for the File Manager (Chrome 86+, Firefox 111+, Safari 15.2+)
• Service Worker support for offline capability

License

MIT