Security Architecture

Encryption Protocol

Lakrion implements the Signal Protocol with PQXDH post-quantum key exchange:

• • PQXDH Key Agreement - Post-Quantum Extended Diffie-Hellman with ML-KEM-768 hybrid encryption
• • Double Ratchet - Per-message forward secrecy with key evolution
• • Sender Keys - Efficient group encryption with E2E guarantees
• • AES-256-GCM - Authenticated encryption for message content
• • Post-Quantum Cryptography - ML-KEM-768 hybrid, active for messages, calls, PTT, and video
• • Deniable Authentication - MAC-based auth that doesn't create proof of authorship

Metadata Protection

Beyond message encryption, we protect communication metadata:

• • Sealed Sender - Server cannot see who sends messages; sender ID is inside the encrypted payload
• • Sender Unlinkability (ESID) - Ephemeral sender IDs prevent linking messages to identities
• • Uniform Message Envelopes - All messages padded to fixed sizes, hiding content type and length
• • Control Camouflage - Typing indicators and read receipts disguised as regular messages
• • Cover Traffic - Self-addressed dummy messages to mask communication patterns. Enabled by default.
• • Timing Obfuscation - Server-side timing is randomized to resist traffic analysis
• • No Contact Graph - We don't store or expose your contact relationships
• • Connection Randomization - Randomize connection patterns to prevent fingerprinting

Post-Compromise Security (PCS)

If a session is compromised, Lakrion automatically recovers security:

• • Automatic PCS - Strong, automatic recovery without user intervention
• • Forced DH Ratchet - Recovery events trigger immediate key rotation
• • Silent Session Burn - Suspicious sessions automatically destroyed and rebuilt
• • Identity Blinding - Identity keys can rotate without breaking sessions
• • Key Aging - Keys auto-expire and are purged on schedule

Dormant Architecture (LDA)

Our novel security architecture protects against zero-click exploits:

• • Code Not Loaded - High-risk subsystems (audio, codecs) completely unloaded until needed
• • Mutual Consent - Both parties must agree before loading call/PTT subsystems
• • Time-Bounded - Active subsystems automatically return to dormant state
• • Exploit Resistance - Pegasus-style attacks can't target code that isn't loaded

Read the full LDA specification →

Network Privacy

• • Tor Support - Route all traffic through Tor with automatic kill-switch
• • TURN-Only Calls - Voice calls always relayed; your IP never exposed to peers
• • ACK Batching - Three modes to batch acknowledgments and reduce timing leaks
• • Traffic Shaping - Configurable jitter and timing patterns (3 modes)
• • TLS 1.3 - All connections use modern TLS with certificate pinning

Privacy by Default

• • No Phone Number - Create accounts with just an account key
• • Screenshot Blocking - Enabled by default
• • Incognito Keyboard - Disables keyboard learning by default
• • Activity Indicators OFF - Typing, online status, read receipts all off by default
• • Calls OFF - Voice/PTT disabled by default, enable per-contact
• • Per-Chat Controls - Toggle calls, media, and activity per conversation
• • Encrypted Local Storage - Database and media files encrypted on device

Server Architecture

• • 24h Auto-Delete - Undelivered messages purged after 24 hours
• • Minimal Logs - Only operational data; no message content or metadata
• • EU Jurisdiction - Servers in Germany under EU privacy law
• • Cannot Read - E2E encryption means we see only encrypted blobs
• • Cannot Identify Sender - Sealed sender hides who sent each message

Verification

Verify contacts through safety numbers - a unique fingerprint derived from both parties' keys. Compare via QR code in-person or by reading numbers aloud.

Voice Calls

• • E2E Encrypted - Per-session ephemeral keys, ChaCha20-Poly1305
• • IP Protected - All calls routed through TURN relay
• • Opus Codec - High-quality audio with RNNoise suppression
• • Off by Default - Calls only enabled when you explicitly allow them

Audits & Transparency

• • Protocol - Self-published specification (independent audits planned)
• • LDA Specification - Published on Zenodo for technical review
• • Open Source Client - Planned

What We Can't Protect Against

No system is perfect. Encryption doesn't protect against:

• • Device compromise (malware with root access)
• • Screenshots by recipients (we block, but determined attackers can work around)
• • Physical access to unlocked devices
• • Weak device security (no PIN/biometric)
• • Social engineering
• • Compromised contacts forwarding your messages

Security is a chain. We provide the strongest link we can.