Fileshare

Direct browser-to-browser payloads via WebRTC. Hardened with AES-GCM 256 & ECDH.

fileshare is a high-performance, zero-knowledge file distribution utility. It demonstrates advanced orchestration of browser-native APIs to achieve secure, serverless data streaming with a focus on memory efficiency and cryptographic integrity.

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Operational Overview

• Runtime: Optimized for Bun (Fastest JS all-in-one toolkit).
• Networking: WebRTC DataChannels (P2P) orchestrated via WebSockets.
• Security: WebCrypto API for hardware-accelerated AES-GCM 256-bit encryption.
• Privacy: ECDH (Elliptic Curve Diffie-Hellman) key exchange for zero-knowledge transfers.
• Interface: Matte-phosphor industrial UI built with Preact and CSS Modules.

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Technical Specification

Layer	Technology	Implementation
Runtime	Bun	Used for high-speed dependency management and bundling.
Frontend	Preact + TS	Reactive state management for real-time progress tracking.
Transport	WebRTC	Direct Peer-to-Peer DataChannels to bypass server bottlenecks.
Signaling	WebSockets	Lightweight node discovery and session negotiation.
Security	WebCrypto	Native AES-256-GCM encryption with chunk-level integrity.

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Engineering Highlights

• Asynchronous Backpressure Management: Implements a manual flow-control loop using bufferedAmount. By monitoring the RTCDataChannel buffer and pausing the stream when it exceeds 16MB (BUFFERED_AMOUNT_HIGH), the system prevents memory overflow and packet loss during high-speed transfers.
• Zero-Knowledge Key Exchange: Leverages ECDH (P-256) to derive a shared secret locally. The signaling server brokers the handshake but is cryptographically incapable of deriving the session key or viewing the file data.
• Atomic Binary Framing: Utilizes custom encodeFrame and decodeFrame utilities to handle binary chunk indexing. This ensures file integrity and proper reassembly even when dealing with massive binary streams.
• Hardware-Accelerated Encryption: Uses the native WebCrypto API for AES-GCM 256-bit encryption. This offloads cryptographic tasks to the browser's optimized background processes, ensuring the UI remains responsive at 60fps during transfers.
• Memory-Efficient Chunking: Fragments files into 64KB chunks using Blob.slice() and ArrayBuffer. This allows the application to transfer multi-gigabyte files without exceeding the browser's heap limit or crashing the tab.

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Security Architecture

This system utilizes a zero-knowledge architecture. File data never touches a server; the WebSocket signaling layer only facilitates the initial metadata handshake.

1. Peer Discovery: Nodes connect to a signaling room via WebSockets.
2. Key Exchange: Peers derive a shared secret locally using ECDH; private keys never leave the client.
3. Encrypted Stream: Files are fragmented into binary chunks, encrypted, and pushed through the WebRTC pipe.
4. Hardware Acceleration: Utilizes native window.crypto for low-latency encryption that doesn't block the UI thread.

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Development

git clone https://github.com/alpercitak/fileshare
cd fileshare
bun install
bun run dev

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License

MIT