KopiCat

Secure clipboard sharing via simple links.

Share text, code, and secrets — end-to-end encrypted, no tracking.

Features

• 🔐 AES-256-GCM client-side encryption with PBKDF2 key derivation
• 🌐 Fully decentralized — single ICP canister, no central servers
• 📱 QR code sharing — send clips to nearby devices
• ⏳ Auto-expiry — configurable TTL with lazy cleanup
• 🔥 Burn after read — optional one-time delivery
• 💾 IndexedDB persistence for saved clips
• 📡 Receive mode — generate a receiving clip and let others send to you
• 🔍 SHA-256 verification — frontend computes hash, backend validates integrity

Quick Start

icp deploy # deploy backend + frontend
pnpm dev # start frontend dev server (proxies /api to local replica)
pnpm test# run tests
pnpm check # type check

Architecture

• Backend: Motoko persistent actor with create_clip (update), get_clip (query), and get_stats (admin-only)
• Frontend: Svelte 5 SPA, static build → dist/ → asset canister via icp sync
• Crypto: AES-256-GCM; ciphertext = salt(16) + iv(12) + ciphertext; password stays in URL fragment

Security

• Password never leaves the browser — stored in #fragment, never sent to server
• Canister stores only encrypted blobs; plaintext never exposed on-chain
• SHA-256 checksum verified on create_clip to detect corruption
• get_stats restricted to canister creator

Project Structure

backend/main.mo # Motoko persistent actor — clip CRUD + sha256 verification
frontend/
├── lib/
│ ├── api/ # ICP client, IndexedDB store, Svelte writables
│ ├── crypto.ts # AES-256-GCM + SHA-256
│ └── components/ # Svelte 5 runes
├── routes/ # /, /send, /share, /view, /list, /faq
└── service-worker.ts # Workbox PWA

Contributing

PRs welcome.

License

MIT