In this paper, we propose a 3-level heterogeneous network model for WSNs to enhance the network lifetime, which is characterized by a single parameter. Depending upon the value of the model parameter, it can describe 1-level, 2-level, and 3-level heterogeneity. Our heterogeneous network model also helps to select cluster heads and their respective cluster members by using weighted election probability and threshold function. We compute the network lifetime by implementing HEED protocol for our network model. The HEED implementation for the existing 1-level, 2-level, and 3-level heterogeneous network models are denoted as HEED-1, HEED-2, and HEED-3, respectively, and for our proposed 3-level heterogeneous network model, the SEP implementations are denoted as hetHEED-1, hetHEED-2, and hetHEED-3, respectively. As evident from the simulation results, the hetHEED-3 provides longer lifetime than that of the HEED-3 for all cases.

Pixel value differencing is a steganographic technique for gray scaled images. In this paper, we propose a modified pixel value differencing image steganographic scheme with least significant bit substitution method. Our method divides the cover image into the blocks of two consecutive pixels and calculates the absolute difference between the pixels of a block similar to [1, 2]. If the difference is less than a particular threshold, i.e. 15 (in this paper) than 4 bits of secret data are taken and these bits are embedded onto the LSBs of the block's pixels through least significant bit substitution method otherwise the number of bits to be hidden are selected based on some characteristics of the block and hidden. The experimental results show that our method significantly improves the quality of stego image as compared to the [1, 3] and have sufficient payload.