Devices used in the Wireless Sensor Network are very small and compact in size, and this technology is expected to connect billions of devices in the future. Wireless Sensor Network used in IoT is expected to generate heaps of data and security can be a great threat. Due to its compactness, resource constraints and low powered it is difficult to use conventional encryption algorithms because of expensive computation, complexity and power used in encryption and it also requires many rounds to encrypt, leads to wasting of constrained energy of the WSN devices. In this paper, a comparison is proposed between two lightweight encryption algorithms based on Feistel structure named Secure Force (SF) and Secure Internet of Things (SIT) implemented by using a simple architecture that only consists of simple mathematical operation (AND, OR, XOR, XNOR, Shifting, Swapping). This can reduce the load on encoder because complex key expansion process is only carried at the decoder. Confusion and diffusion of the image matrix, and different substitution and permutation techniques are also included to increase the complexity of the cipher. The proposed comparison helps us to evaluate which algorithm is better in terms of architecture, time complexity, flexibility, and security.