Real time implementation of Elliptic Curve Cryptography over a open source VoIP server

This paper presents the design and the implementation of Elliptic Curve Cryptography in an Asterisk VoIP server which serves as an exchange for placing voice calls over the internet. Voice over internet protocol refers to the transmission of speech encoded into data packets transmitted across networks. VoIP networks are prone to confidentiality threats due to the weak keys used by the AES algorithm for encryption of the VoIP packets. So, in order to strengthen the key for encryption/decryption, Elliptic Curve Diffie-Hellman (ECDH) Algorithm key agreement scheme is employed with smaller key sizes resulting in faster computations. The elliptic curve used in this paper is a modified NIST P-256 curve and key generation algorithm using split exponents for fast exponentiation has been implemented to speed up and increase the randomness of key generation. The implementation of split exponents also help in increasing the security of the keys generated. The key generated by ECDH is highly secure because the discrete logarithmic problem is very difficult in this scheme. This Method is successfully carrying out voice calls on VoIP clients connected to the internet. This ECDH key exchanging mechanism for voice calls in real time is implemented on an Asterisk PBX (Private Branch eXchange), using AGI(Asterisk Gateway Interface) server.