Security of wireless sensor networks (WSN) is an important feature, as they are used in critical applications such as surveillance, monitoring, tracking and controlling etc. Secure and reliable communication is highly important in delivering critical information correctly and in-time by low-powered sensor motes (SM). Many secure WSNs protocols have been proposed but they have focused primarily on denial-of-communication at the routing or medium access control levels. Although WSNs have interesting distinctiveness (i.e., minimum set-up cost, unattended network operation), and because of the wireless medium (i.e., there are no gateways or routers to observe data flow), the security of these networks is the main issue, particularly when privacy is the main theme. Secure communication in WSNs reclines in the security of their routing protocols. However, resource bound security solutions are needed for WSNs. This paper has proposed novel security mechanism by combining features of two security architectures in WSNs, i.e., TESLA from SPINE and Bloom Filters (BF) from MiniSec. We have used TOSSIM for simulation and showed that our proposed mechanism perform better than other security schemes.