Body area network (BAN) has recently emerged as a promising platform for future research and development. The applications are myriad and encompass a wide range of scenarios, including those in not only medicine but also in everyday activities. However, while the applicability and necessity of BAN have been firmly assured, the underlying technological platforms to practically realize these networks are still in the developmental stages, with many outstanding key problems to be addressed. Due to their envisioned domains of applicability, an important problem in BANs is security and user privacy. Providing security in a practical BAN configuration is challenging due to various conflicting resource constraints. In this paper, the focus is to study signal processing methods for delivering secure communications in BANs, particularly when using biometrics. An optimization framework is presented to aggregate various methods, enabling overall quality of service (QoS) regulation in an integrated and flexible manner. In particular, this resource allocation approach is shown to be effective in managing security solutions for BANs.