Reducing packet loss in CBC secured VoIP using interleaved encryption

In this paper we introduce the use of interleaved encryption to improve quality of service (QoS) in VoIP secured using cipher block chaining (CBC) mode ciphers. In current secure VoIP implementations using CBC mode ciphers, a late ciphertext block causes a decryption failure in the next ciphertext block due to inter-block decryption dependencies. The decryption failure in turn further degrades the QoS of the overall communication. This paper introduces an approach to relax the inter-block decryption time constraints such that the QoS of CBC mode secured VoIP asymptotically approaches that of non-secure VoIP. Experimental results on a number of captured VoIP traces shows that packet loss rate can be reduced by 1-2% depending on network conditions.