User-friendly voice and messaging app with enterprise security.
  • No backdoors, no man-in-the-middle attacks
  • Unlimited peer-to-peer calling with out-of-network calling
  • Unlimited peer-to-peer calling
  • Secure messaging and file transfers
  • Scheduled burn functionality on both ends
  • Available for any Android or iOS device

No backdoor policy

At Silent Circle, we maintain a strict no backdoor policy. The encryption keys to private communications remain in your hands and your hands alone. Your enterprise stays at the highest level of security at all times.

Private by design

Designed by the best minds in mobile technology, encryption, security and privacy, our fundamentally different technology sets the standard for enterprise privacy in today’s mobile-first world.

Proprietary technology lets business thrive

Enterprise mobile security should work silently and effectively in the background. It should also amplify business opportunities. Our devices and services focus on keeping your data secure at all times while simultaneously providing for the free flow of business communication. A pioneering “mobile first” vision of technology is present in all our offerings. Silent Circle maintains an industry leadership position in the rapidly changing world of mobile communications security.

Built on a fundamentally different protocol

When two Silent Circle users call or video chat each other, that transmission is secured and encrypted end-to-end on our crystal-clear secure network. ZRTP provides true peer-to-peer key negotiation and management for secure VOIP communication.

Proprietary military-grade technology

ZRTP is a cryptographic key-agreement protocol to negotiate the keys for encryption between end points in a Voice over Internet Protocol (VoIP) call. ZRTP uses Diffie–Hellman key exchange and the Secure Real-time Transport Protocol (SRTP) for encryption.


ZRTP stands for “Zimmermann Real-time Transport Protocol” and was developed by Silent Circle’s own, Phil Zimmermann. This proprietary technology has perfect forward secrecy, meaning the keys are destroyed at the end of the call. This fully prevents compromising the call contents at a later date even if key material is somehow disclosed.


  • End-to-end encryption.
  • Enhanced ZRTP.
  • Full time man-in-the-middle detection.
  • All mobile endpoints secured.
  • Rapid deployment, convenient central control.
  • Easy web based management.
  • No additional hardware or additional chips required for Silent Phone secure messaging.