The widespread application of wireless sensor networks (WNSs) is obstructed by the severely limited energy constraints and security threat for sensor nodes. Since traditional routing and security schemes are not suited for these networks, a large part of research focusses on energy efficient routing protocols while extending the network lifetime. Uneven distribution of communication loads result in network partitioning. Traditional novel en-route filtering approaches, notably commutative cipher based en-route filtering (CCEF) saves energy by early filtering of false reports. However this approach main focus is security not network lifetime is limited by fixed paths and underlying routing not suitable for WSNs. In order to cater these problems we propose energy efficient routing and pre-deterministic key distribution with dynamic path selection in CCEF. Modified CCEF (MCCEF) aims at saving energy and extending network lifetime while maintaining filtering power as in CCEF. Experimental results demonstrate the validity of our approach with an average of three times network lifetime extension, 5.022% energy savings, and similar filtering power as the original scheme.