| With the proliferation of personal communication systems (PCS) and the advent of ubiquitous access to multimedia content over the Internet, PCS users are more likely to have their data traverse a heterogeneous internetwork. Given the insecure nature of wireless links and the Internet, more users will demand end-to-end confidential communications. However, the low reliability of interference-limited wireless networks, the burst-loss nature of packet-switched networks, and the delay sensitivity of interactive continuous-media applications raise special challenges to providing both good subjective quality and confidentiality. In particular, we show that existing encryption systems exhibit severe error multiplication properties in heterogeneous internetworks, especially those with wireless transport. Thus, using these systems to provide end-to-end confidentiality, in such an environment, implies degradation in Quality of Service (QoS) in exchange for data confidentiality.; Using bit-error rate (BER), traffic capacity, and delay as measures of QoS, this dissertation characterizes and quantifies this trade-off. Through subjective experiments, we show that the perceptual degradation in subjective quality caused by confidentiality closely follows the quantitative degradation in BER. Then, using a direct-sequence code-division multiple-access (DS-CDMA) system as an example, we show that system traffic capacity can be reduced between a factor of two (2) and a factor of four (4), when using current secret-key encryption systems for confidentiality. Thus, we promote the need for error-robust encryption (ERE) systems.; We propose and analyze two ERE techniques in this dissertation. The first technique eliminates this dependency of QoS on confidentiality and the second technique substantially mitigates it, but does not eliminate this dependency. These two techniques have been implemented in software and are now part of an Internet telephony tool. Results from experiments using this tool are presented to demonstrate the effectiveness of these techniques. |
