The IEEE 802.15.4 standard for Low Power Wireless Personal Area Networks (LoWPANs) has emerged as a promising technology to bring envisioned ubiquitous paragon, into realization. Efforts are being carried on to integrate LoWPANs with other wired and wireless IP networks. Designing a security solution becomes a challenging task as it involves threats not only from wireless domain but also from extremely mature IP domain. We present a security framework that can act as basic design goal for any security architecture proposed for 6LoWPAN. Proposal include an authentication protocol,a malicious node removal mechanism (TASER) and a unified security framework with three key management schemes, SACK, SACK-P, and SACK-H that incorporate symmetric, asymmetric and the hybrid cryptography , respectively. We have evaluated the key management schemes against a broad range of metrics such as energy, resource utilization, scalability and resilience to node compromises.Our results substantiate arelationship between the level of security and resource-utilization and form a design benchmark for security frameworks.