ZORG

Zorg is an implementation of the ZRTP protocol. ZRTP is an in-band key exchange protocol for SRTP, based on either the Diffie–Hellman (D–H) or the elliptic curve Diffie–Hellman (ECDH) algorithms, with Man-in-the-Middle protection based on human voice recognition. 

Coupled with an SRTP implementation, Zorg provides VoIP security with Diffie–Hellman (up to 3072 bits) or elliptic curve Diffie–Hellman (up to 384 bits) for key exchange, AES (up to 256 bits) for confidentiality and HMAC-SHA1 for authentication.

Zorg implementations are developed in cross-platform C++ language and Java language in order to run on most mobile phones and all desktop platforms.

via zrtp.org