ASH

Secure, ephemeral messaging for high-security, low-frequency communication.

What is ASH?

ASH is a messaging application that uses One-Time Pad (OTP) encryption to provide information-theoretic security. It is designed for situations where confidentiality matters and trust in infrastructure is limited.

ASH prioritizes:

• Correctness over convenience
• Human-verifiable security
• Minimal trust in infrastructure
• Deliberate user actions

ASH is not designed for everyday chat.

How it works

1. Ceremony: Two devices establish a shared One-Time Pad through an offline, QR-based transfer
2. Verification: Users confirm matching mnemonic checksums
3. Messaging: Messages are encrypted with OTP and relayed through an untrusted backend
4. Burn: Either party can irreversibly destroy the conversation

Architecture

┌────────────┐
│   Users    │
└─────┬──────┘
      │
┌─────▼──────┐
│  iOS App   │  (SwiftUI)
└─────┬──────┘
      │  FFI boundary
┌─────▼──────┐
│   core     │  (Shared Rust Core)
└─────┬──────┘
      │
┌─────▼──────┐
│  Backend   │  (Rust Relay)
└────────────┘

• core: Rust library containing all cryptographic logic
• apps/ios: SwiftUI iOS application
• backend: Untrusted relay that never sees plaintext

Note: Android support is planned for future versions.

Security Model

ASH provides:

• Message confidentiality against network and backend observers
• Information-theoretic security via One-Time Pad
• Pad non-reuse enforcement by design
• Human-verifiable ceremony correctness

ASH does not provide:

• Anonymity at the network level
• Protection against device compromise
• Protection against malicious participants
• Forensic-level secure deletion

See docs/threat-model.md for the complete threat model.

Documentation

Document	Description
Scope	What's in and out of v1
Architecture	System design and boundaries
Threat Model	Security guarantees and limitations
Ceremony	Pad establishment protocol
Framing	QR frame format specification
Data Lifecycle	How data is handled and destroyed
Backend Contract	API invariants and behavior
Ethics	Ethical position and boundaries
Glossary	Project terminology

Security

See SECURITY.md for vulnerability reporting.

License

See LICENSE for details.