Robert John Rance

Secure and efficient voice‐over‐IP in a cdma2000® Network

This paper examines how to provide secure and efficient voice-over-IP service on a cdma2000 network. Various alternative solutions and their relationship to header compression techniques are discussed. We propose a new method of end-to-end encryption that could be used to provide privacy even when Header Removal, a cdma2000-specific technique where IP/UDP/RTP headers are discarded before transmission over the air, is in use. The new method relies on a novel variable-length block cipher that can be re-used with fixed parameters across many voice frames, eliminating the requirement to carry precise cryptographic synchronization with each and every voice frame. Instead, the parameters to the block cipher are varied on an infrequent basis, and synchronization information is communicated from the encryptor to the decryptor by overwriting the occasional voice frame, with minimal impact on resulting voice quality. The method offers provable security guarantees given some assumptions about the amount of entropy contained in the encoded speech data.