Features

Everything you need for truly private communication — designed to be simple, secure, and available everywhere. Free encrypted communication for all, with optional telephony subscriptions.

Messaging

Encrypted Messaging

Send text messages, photos, videos, documents, and voice notes — all protected with end-to-end encryption. Cyfero utilises the Signal Protocol, implementing the X3DH key agreement and Double Ratchet algorithm independently based on the openly published protocol specifications.

This means every conversation benefits from forward secrecy: compromise of a long-term key does not compromise past session keys. Each message is encrypted with a unique key derived through the ratchet, and keys are automatically rotated with every exchange.

  • Text, media, and file sharing with AES-256-GCM encryption
  • Forward secrecy and post-compromise security via cryptographic ratcheting
  • Delivery receipts and optional read receipts
  • Safety number verification for identity confirmation
  • Privacy-preserving contact discovery using local hashing
Encrypted Calling

Encrypted Voice & Video Calls

Crystal-clear voice and video calls protected with end-to-end encryption. Call signalling is encrypted using the Signal Protocol, while media streams use SRTP over peer-to-peer WebRTC connections for minimal latency.

These are Cyfero-to-Cyfero calls between registered users — free for all Cyfero accounts and available on Android, iOS, and Web. No phone number or subscription required.

  • End-to-end encrypted signalling and SRTP media streams
  • Peer-to-peer WebRTC with ICE/STUN for direct connections
  • TURN relay for NAT traversal in restrictive networks
  • Available to all Cyfero users at no cost
VoIP Subscription

PSTN Calling via VoIP

For users who need to make or receive calls to regular phone numbers, Cyfero offers an optional recurring VoIP subscription. This service connects your Cyfero app to the public switched telephone network (PSTN), giving you a dedicated phone number and the ability to call landlines and mobiles worldwide.

VoIP PSTN calling uses standard telephony infrastructure and is a separate service from Cyfero's end-to-end encrypted communication features. The Signal Protocol is not used for PSTN calls, as these traverse the public telephone network where end-to-end encryption is not applicable.

  • Dedicated VoIP phone number provisioning
  • Outbound calls to landlines and mobile numbers globally
  • Inbound PSTN calls to your dedicated Cyfero VoIP number
  • Transparent per-minute rates for international destinations
  • Recurring billing with self-service subscription management
  • Accessible from all Cyfero apps (Android, iOS, Web)

Important: VoIP PSTN calling is not a replacement for traditional telephone services and should not be relied upon for emergency calls. This is an optional premium feature — Cyfero's core encrypted communication features remain free for all users.

Multi-Platform

One Account, Every Device

Cyfero is available on Android, iOS, and Web. Link multiple devices to your account and optionally sync your encrypted conversations across them.

Android

Full-featured app with SMS management, call history, and secure messaging. Designed to serve as your default communication app.

  • - Native SMS via content resolver
  • - PSTN call history integration
  • - Encrypted Cyfero messaging and calls
  • - Optional VoIP subscription

iOS

Secure messaging and calling on iPhone and iPad. Built with the same encryption standards as the Android app.

  • - Encrypted Cyfero messaging and calls
  • - Native Swift implementation
  • - Optional VoIP subscription
  • - Push notification support

Web

Access Cyfero from any browser at web.cyfero.me. Full messaging and calling without installing anything.

  • - Encrypted Cyfero messaging and calls
  • - Browser-based WebRTC calling
  • - Optional VoIP subscription
  • - No installation required

Security at Every Layer

From application-level encryption to transport-layer hardening, Cyfero is built to protect your data at every step. All security features are developed in-house with no third-party dependencies for message routing or storage.

Signal Protocol Implementation

Independent implementation of the X3DH key agreement and Double Ratchet algorithm based on the openly published Signal Protocol specifications. Provides forward secrecy and post-compromise security for all encrypted communications.

Certificate Pinning

SPKI SHA-256 pin validation on all TLS connections to Cyfero servers, preventing MITM attacks even with compromised certificate authorities.

Encrypted DNS Resolution

DNS-over-HTTPS (DoH) prevents DNS-based surveillance and ensures domain lookups remain confidential.

Traffic Normalisation

WebSocket frame padding masks message sizes, preventing traffic analysis from revealing communication patterns.

Argon2id Key Derivation

Memory-hard password hashing with Argon2id protects credentials against brute-force and side-channel attacks.

Zero-Knowledge Identifier Storage

User identifiers are stored exclusively as irreversible HMAC-SHA256 hashes — the server cannot recover your phone number or email.

Privacy-Preserving Contact Discovery

Contacts are hashed locally before querying. Phone numbers and email addresses never leave your device in plaintext.

Zero Knowledge Server

The signalling server, written in Rust for memory safety, acts purely as a relay. It routes encrypted payloads it cannot decrypt. No message content is ever stored server-side.

Hardened OS Compatibility

Designed and tested to function smoothly on privacy-hardened operating systems with graceful fallback when platform services are restricted.