Cryptographic Security Model

Security That Is Structural,
Not Configurable

Peer-reviewed protocols. No security settings to misconfigure. Confidentiality, integrity, forward secrecy, and post-compromise security — by default, for every conversation.

Protocol Stack

Cryptographic Foundation

Identity

Ed25519 + X25519

Long-term signing and identity keys generated on-device during account creation. Private keys never leave the device. The server stores only public material.

Key Agreement

X3DH

Extended Triple Diffie-Hellman with identity keys, signed prekeys, and one-time prekeys. Mutual authentication, forward secrecy, and deniability. One-time prekeys consumed after use.

Session Encryption

Double Ratchet — AES-256-GCM

Every message derives a unique key from a ratcheting chain. Compromising one key exposes nothing about past or future messages. Forward secrecy is automatic, not optional.

Group Security

MLS — Ratchet Tree

Each group member holds independent leaf node key material. Adding or removing members triggers epoch-wide rekeying. Forward secrecy and post-compromise security at any scale.

Multi-Device

Sesame Protocol

Each device maintains independent cryptographic identity. Session multiplexing without shared private keys. Device compromise is isolated by architecture.

Authentication

FIDO2 / WebAuthn

Passkey-based proof-of-possession. No passwords transmitted, stored, or phishable. Authentication is cryptographic, not credential-based.

Server Model

Zero-Knowledge Server Architecture

The server is an untrusted relay. Its role: public key distribution and encrypted payload forwarding. It has no capability to access communication content. This is not a policy. It is mathematics.

Cannot Read Messages

All content encrypted client-side before transmission. The server processes only opaque ciphertext.

Cannot Identify Contacts

Contact lists encrypted with per-user keys before sync. The server stores an opaque blob it cannot interpret.

Cannot Access Session Keys

Shared secrets derived through Diffie-Hellman exchanges the server cannot compute. No key material stored server-side.

Cannot Reconstruct Patterns

No persistent logs of communication patterns, timing, or social graph. Metadata is excluded by architecture.

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Full cryptographic protocol documentation available for independent security review. Contact us for technical architecture discussions.