VoIP Security: Improving Quality of Service through the Analysis of Secured Transmission

Abstract

VoIP as a packet switched system is clearly one of the most important evolving trends in computing and telecommunications. However, just like many other new Information technology trends, VoIP introduces both security risks and opportunities for the IT world, viable solutions of which are required. The use of publically verified cryptographic algorithms to ensure confidentiality of VoIP traffic transmitted over insecure public networks as the Internet cannot be overemphasized.  Nonetheless, the uses of cryptographic algorithms yet imposes a delay overhead and packet size overhead on VoIP, which is unconnected to the processing time required to encrypt/decrypt bits or blocks of data and the increase in packet size due the block size of the encryption algorithm. This delay levied is dependent on the mode of operation of the cryptographic algorithms. Mindful of the fact that other components like voice codecs and network bandwidth also contributed delay capabilities on VoIP traffic, and additions of security overheads, there exists a threshold point where an increase in call volume exerts a negative effect on pre-established calls with respect to time and the rate of packet loss. This study sought to determine the combination of cryptographic algorithms, cipher mode and voice codec that holds the uppermost threshold point, before the latency and rate of packet loss of active calls goes past ITU acceptable standards; for one way latency in both plain and encrypted VoIP traffic of 150ms and 200ms respectively and 5% packet loss rate. Through simulation of appropriate scenarios, results indicates that each of the encryption algorithms (AES, DES and 3DES) append additional overhead on the e2e delay and rate of packet loss during VoIP transmission. Also revealing that VoIP-supported codecs are faster and have a higher threshold in terms of  the number of calls before the e2e delay and the rate of packet loss exceeds the acceptable limit for encrypted and plain VoIP e2e delay and packet loss rate.