SecretCalls

Secret Calls by h2quadrat is a telephony solution for companies wishing to encrypt their smartphone-to-smartphone calls.
Calls are encrypted using the 256-bit Advanced Encryption Standard (AES), one of the world’s most widely used and secure encryption methods. Dynamic key negotiation is performed for every call to guarantee maximum security. The encrypted voice communication service uses VoIP (SIP TLS for the signaling and ZRTP for the voice call) and WiFi, 3G (UMTS) and 4G (LTE) mobile data networks.

Please note: The SecretCalls app can only be used in combination with the h2quadrat server.