Mphone XR uses the AES encryption algorithm with a key of 256-bit and TwoFish. This is done to guarantee the reliability of the cipher. The encryption algorithm AES-256 is used in the state structures of the USA for encryption of information classified as SECRET and TOP SECRET. So, the use of a single encryption algorithm AES-256 already makes the information transmitted by MPHONE XR secure, and an additional overlay algorithm Twofish, give perfect 100% protection.
Voice call security is ensured by a combination of multiple technologies and protocols. For signaling (for example, about the beginning of a call), the SIP TLS Protocol is used. The audio channel is protected using symmetric cipher AES/Twofish 256 bits, which is using ZRTP. The ICE Protocol decides which method to use for communication of subscribers: if the connection through STUN has passed, then P2P with ZRTP is used, if the proxy connection does not pass directly, then TURN with ZRTP is used.