Wireless Sensor Networks (WSN) is the accumulation of large number of tiny, low power autonomous devices. By the very nature, WSN are prone to attack and difficult to secure, manage, even for most savvy network administrators. Security algorithms are requisite for protecting data transmission in WSN, since unlicensed wireless bandwidth is used for data communication. In this work a lightweight encryption algorithm with modified key generation by fusing logistic map and tent map is proposed and the same is implemented in ALTERA DE1 cyclone II FPGA which occupies only 1550 logic element for 128 bit key size and a maximum throughput of 200 Kbps is achieved. © 2016 The Authors.