Onera E2EE Architecture Whitepaper

Version: 1.0
Date: January 2026
Authors: Onera Security Team

Abstract

Onera is a privacy-focused AI chat application that implements true end-to-end encryption (E2EE) for all user data. This whitepaper details Onera's cryptographic architecture, which ensures that sensitive information—including chat messages, API credentials, and personal notes—remains encrypted at rest and in transit, with decryption possible only on authorized user devices.

Our architecture employs a defense-in-depth approach combining:

• XSalsa20-Poly1305 for authenticated symmetric encryption
• X25519 for asymmetric key exchange and sharing
• Argon2id for memory-hard password-based key derivation
• 3-share XOR-based key sharding requiring compromise of multiple independent systems
• WebAuthn PRF for hardware-bound passkey authentication

The server operates exclusively as an encrypted blob store, never accessing plaintext user data. LLM API calls are made directly from the client to providers, bypassing Onera infrastructure entirely.

Introduction

Motivation

As AI assistants become integral to daily workflows, users increasingly share sensitive information—personal conversations, proprietary code, API credentials, and confidential business data. Traditional AI chat applications transmit and store this data in plaintext on provider servers, creating significant privacy and security risks.

Onera addresses this fundamental issue by implementing end-to-end encryption where:

• All sensitive data is encrypted client-side before transmission
• The server stores only encrypted blobs it cannot decrypt
• Decryption keys never leave the user's devices
• LLM API calls connect directly to providers, bypassing Onera servers

Design Goals

1. Zero-Knowledge Server: The server cannot access plaintext user data under any circumstances
2. Defense in Depth: Multiple independent security layers protect user data
3. Usability: Strong security without sacrificing user experience
4. Recovery: Multiple paths to recover access without compromising security
5. Multi-Device: Seamless synchronization across authenticated devices
6. Transparency: Open architecture that can be independently audited

Document Scope

This whitepaper covers:

• Cryptographic algorithms and their selection rationale
• Key generation, derivation, and management
• Data encryption and decryption flows
• Threat model and security analysis
• Recovery and multi-device mechanisms

Implementation details reference the open-source codebase at /packages/crypto/.

Table of Contents