OtterSeal Documentation

🦦 Zero-knowledge encrypted notes and secrets

👉 Try it now: Open OtterSeal Web App

What is OtterSeal?

OtterSeal is a suite of packages for building zero-knowledge encrypted applications:

• @otterseal/core — Cryptography library (AES-256-GCM + HKDF)
• @otterseal/cli — Command-line tool for notes and secrets
• @otterseal/rest-api — Backend API for self-hosting

All encryption happens client-side. The server never sees your plaintext content or encryption keys.

Quick Start

Using the CLI

# Create a secret
oseal secret send "This is secret"

# Read your notes
oseal note read "my-title"

Using the Core Library

import { deriveKey, encryptNote } from '@otterseal/core'

const key = await deriveKey('my-title')
const encrypted = await encryptNote('secret content', key)

Self-Host the API

# See: @otterseal/rest-api deployment guide

Architecture

graph TD A["🌐 Client<br/>(Browser/CLI)"] B["@otterseal/core<br/>Web Crypto API<br/>HKDF • AES-256-GCM"] C["REST API<br/>(WebSockets)"] D["Database<br/>(Encrypted)"] A --> B B -->|Encrypted Data| C C --> D style A fill:#0d9488,stroke:#0f766e,stroke-width:2px,color:#fff style B fill:#14b8a6,stroke:#0d9488,stroke-width:2px,color:#fff style C fill:#2dd4bf,stroke:#14b8a6,stroke-width:2px,color:#000 style D fill:#f0fdfa,stroke:#0d9488,stroke-width:2px,color:#0d9488

Security First

• ✅ Web Crypto API — Uses native browser cryptography (SubtleCrypto)
• ✅ Client-side encryption — Keys never leave your device
• ✅ AES-256-GCM — Industry-standard authenticated encryption
• ✅ HKDF — Cryptographic key derivation with domain separation
• ✅ No passwords — Titles are used directly (more convenient, same security)
• ✅ Open source — Audit the code yourself

Packages

TIP

Each package is independent and can be used standalone or together.

• Core — Cryptography library with AES-256-GCM and HKDF
• CLI — Command-line tool for managing notes and creating secret links
• REST API — Backend API for self-hosting with WebSocket support

Need Help?

• Read the guides on GitHub
• View on GitHub

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