Atlas Associates

Arc / सुरक्षा

बहु-परत E2EE आर्किटेक्चर

प्रकाशित engineering direction वाला व्यावसायिक security product

ILLUSTRATED 1:1 FLOW · 10-SECOND PREVIEW

Encrypted here.Opened there.

A message between people. Private keys stay on the devices; servers carry ciphertext and delivery data.

  1. 01
    Encrypt on device

    The message is encrypted before it leaves.

  2. 02
    Transport ciphertext

    Firestore carries ciphertext and delivery data.

  3. 03
    Open on device

    The recipient’s device decrypts the message.

FunctionsExpiry & notifications
FCMPush notification

Concept animation of one delivery path, not a recording of the app. Other paths, server-visible metadata and exceptions are documented below.

ARCHITECTURE

Arc system architecture

Explore the system diagram

Private keys are stored in the device Keychain / Keystore and never sent to servers. Messages to other people are encrypted on the device before they are sent. Phoenix hands out public PreKeys, Firestore carries ciphertext, receipts and delivery data, and Cloud Functions handle expiry deletion and notifications. Mesh bypasses servers.

One role at a time.

Open full-size diagram

Devices (iOS / Android / macOS)

Arc Protocol

1:1 · libsignal v0.96.2 · Rust FFI

  • PQXDH
  • Kyber-1024
  • Double Ratchet
Private keys
Keychain / Keystore
Decrypted text
SQLite / Hive

Message text and private keys never go to servers (except AI chats, link previews)

Explore the message flows

The dots move in the numbered order. On each of these paths, message text is encrypted on the device before it is sent.

Follow one path at a time.

Open full-size diagram
1:1 message. Post-quantum. First time: fetch B's keys. Encrypt on the device. Send ciphertext only. Notify (no content). Decrypt on B's device. Read / decrypt receipts. Only A's and B's devices can read the text

Post-quantum

1:1 message

  1. First time: fetch B's keys
  2. Encrypt on the device
  3. Send ciphertext only
  4. Notify (no content)
  5. Decrypt on B's device
  6. Read / decrypt receipts

Only A's and B's devices can read the text

On smaller screens, scroll within the diagram. Open the original using the link above.

1:1 is post-quantum (PQXDH). Group messages are not (shared key + X25519 ECIES). On Mesh, nearby Arc phones may forward the ciphertext without being able to read it. Routed relay is in development.

Arc Protocol — 1:1 encryption pipeline

Phase 1

PQXDH

Key agreement with X25519 + Kyber-1024 (post-quantum)

Phase 2

Double Ratchet

A new key for every message

Phase 3

AES-256-GCM

Encrypts message bodies and media

Technology stack

Flutter 3.44
Dart
Riverpod 2.6
Rust
Arc Protocol

App

Flutter 3.44 / Riverpod 2.6 / Rust FFI (libsignal v0.96.2)

Elixir
Phoenix
Cloud Run

Key distribution API

Elixir / Phoenix on Google Cloud Run (europe-west1)

Authentication
Firestore
Storage
Functions
Messaging
App Check
Crashlytics

Delivery and auth

Firebase (Auth / Firestore / Storage / Functions / FCM / App Check / Crashlytics)

Android
Kotlin
Swift

Mesh

BLE implementation (Dart + Android Kotlin + iOS Swift, in-house, beta)

Technical specifications

The four encryption layers

Arc core specification

Arc's core specification is ML-KEM-1024/PQXDH, E2EE for 1:1 and group chats, IGF, and offline Mesh. This Security page documents the scope and technical details.

01

PQXDH कुंजी विनिमय

प्रकाशित engineering direction वाला व्यावसायिक security product

02

Double Ratchet

प्रकाशित engineering direction वाला व्यावसायिक security product

03

AES-256-GCM एन्क्रिप्शन

प्रकाशित engineering direction वाला व्यावसायिक security product

04

XEdDSA हस्ताक्षर (libsignal)

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ML-KEM-1024 पैरामीटर

POST-QUANTUM

NIST FIPS 203 मानकीकृत पोस्ट-क्वांटम कुंजी एनकैप्सुलेशन मेकेनिज़्म।

एल्गोरिदमML-KEM-1024 (via libsignal-client)
NIST सुरक्षा स्तरSecurity category 5
शास्त्रीय सुरक्षा2^128 bit (X25519)
क्वांटम सुरक्षाNIST security category 5
आधारModule Lattice (FIPS 203)
सार्वजनिक कुंजी आकार1,568 bytes
गुप्त कुंजी आकार3,168 bytes
सिफ़रटेक्स्ट आकार1,568 bytes

अनुपालन और मानक

NIST CSF 2.0

NIST फ्रेमवर्क। 6 कार्यों से व्यवस्थित साइबर जोखिम प्रबंधन।

NIST SP 800-53

संघीय सुरक्षा नियंत्रण। FedRAMP आधार।

FIPS 140-3

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NIST SP 800-175B

क्रिप्टोग्राफ़िक एल्गोरिदम चयन मार्गदर्शिका। FIPS 203 आधारित।

ISO/IEC 27001

अंतर्राष्ट्रीय ISMS प्रमाणन। B2B/B2G विश्वास आधार।

GDPR

EU सामान्य डेटा सुरक्षा विनियमन। विश्व का सर्वोच्च सुरक्षा मानक।

UK Cyber Essentials+

ब्रिटिश सरकार प्रमाणित साइबर सुरक्षा प्रमाणन।

NCSC Cloud Security

ब्रिटिश NCSC 14 सिद्धांत। क्लाउड सुरक्षा मूल्यांकन मानक।

अमेरिकी NIST, EU GDPR, ब्रिटिश NCSC और ISO के प्रकाशित दिशानिर्देशों के संदर्भ में डिज़ाइन किया गया। यह कोई प्रमाणन या तृतीय-पक्ष ऑडिट नहीं है।