Internet-of-Things (IoT) is growing network paradigm which enables mutual communication between the user and smart devices using the internet. The IoT devices are susceptible to the security threats, due to placement of restricted computational capabilities of the computing devices in IoT. The conventional encryption algorithm utilizes the high amount of resource block in it which increases the area and power. Moreover, Two Factor Authentication (TFA) scheme based authentication protocols does not have the efficiency to secure the data. Because the random number generated by the TFA is ideal for all IoT devices which are easy to hack by the unauthorized persons. In this Research paper, the Linear Feedback Shift Register (LFSR) based Reconfigurable Physical Unclonable Function (RPUF) is proposed to overcome the security issues caused in the IoT communication. The RPUF is designed based on the LFSR to generate the random number for every clock cycle. Normally, reconfigurable process helps to generate the different output values for every clock cycle. But, it failed to generate different outputs for same input values. Here, LFSR based RPUF helps to generated the different response values even the same challenge is given to the input side. The Lightweight TFA scheme is presented for IoT, where PUF has been considered as one of the major authentication factors. At last, Spartan 6 and Virtex 6 Field Programmable Gate Array (FPGA) performances are calculated for proposed TFA-RPUF-IoT and existing TFA-PUF-IoT protocols. In Spartan 6, TFA-RPUF-IoT protocol occupied 11 slices, 31 LUTs, 42 flip flops which are less compared to conventional TFA-PUF-IoT.

In the last few years Internet-of-Things (IoT) technology has emerged significantly to serve varied purposes including healthcare, surveillance and control, business communication, civic administration and even varied financial activities. Despite of such broadened applications, being distributed, wireless based systems, IoTs are often considered vulnerable towards intrusion or malicious attacks, where exploiting the benefits of loosely connected peers, the attackers intend to gain device access or data access un authentically. However, being resource constrained in nature while demanding time-efficient computation, the majority of the classical cryptosystems are either computationally exhaustive or limited to avoid attacks like Brute-Force, Smart Card Loss Attack, Impersonation, Linear and Differential attacks, etc. The assumptions hypothesizing that increasing key-size with higher encryption round can achieve augmented security often fail in IoT due to increased complexity, overhead and eventual resource exhaustion. Considering it as limitation, in this paper we proposed a state-of-art Generalized Feistel Network assisted Shannon-Conditioned and Dynamic Keying based SSPN (GFS-SSPN) Lightweight Encryption System for IoT Security. Unlike classical cryptosystems or even substitution and permutation (SPN) based methods, we designed Shannon-criteria bounded SPN model with Generalized Feistel Network (SPN-GFS) modelthat employs 64-bit dynamic key with five rounds of encryption to enable highly attack-resilient IoT security. The proposed model was designed in such manner that it could be suitable towards both data-level security as well as device level accesscredential security to enable a "Fit-To-All" security solution for IoTs. Simulation results revealed that the proposed GFS-SSPN model exhibits very small encryption time with optimal NPCR and UACI. Additionally, correlation output too was found encouragingly fair, indicating higher attack-resilience.