Anusuya S. Jeya et.al; International Journal of Advance Research, Ideas and Innovations in Technology © 2018, www.IJARIIT.com All Rights Reserved Page | 512 ISSN: 2454-132X Impact factor: 4.295 (Volume 4, Issue 2) Available online at: www.ijariit.com Data Transmission by Ceaser Cipher Wheel Encryption using Lifi S. Jeya Anusuya hodece@tjsec.in T. J. S. Engineering College, Puduvoyal, Tamil Nadu S. Venket venkatecetjs@gmail.com T. J. S. Engineering College, Puduvoyal, Tamil Nadu V. Logesh Kumar logima97@gmail.com T. J. S. Engineering College, Puduvoyal, Tamil Nadu T. Manoj Gowtham manojgowtham11031997@gmail.com T. J. S. Engineering College, Puduvoyal, Tamil Nadu V. Goutham gouthamnaidu153@gmail.com T. J. S. Engineering College, Puduvoyal, Tamil Nadu R. Gowtham rgowtham987@gmail.com T. J. S. Engineering College, Puduvoyal, Tamil Nadu ABSTRACT The paper describes a microcontroller based secured optical wireless communication system using laser and phototransistor. These days the usage of Wi-Fi has reached to every nook and corner of the world. There are some downsides belong to the usage of Wi-Fi such as those concerning to the speed, limited bandwidth, security and range of its usage. In order to overcome these hitches, we can use the advanced version of Li-Fi which is efficient, high speed, and fully networked wireless communication. If light contains encrypted message then both privacy and prevention from unwanted access along with high data rate can be achievable from Li-Fi. A new encryption technique based on substitution of ASCII value of characters implemented and reliable data transmission carried out. The proposed encryption algorithm primarily follows Caesar Cipher WHEEL substitution, acts similarly with Caesar wheel device by rotating circularly and changes the ASCII value of original message according to predefined values and length of repetition. Encryption of data, transmission, reception, and conversion to original message are implemented successfully using laser, phototransistor, and microcontroller and associated devices. The microcontroller performs as overall controlling and processing unit. Keywords: LASER, OWC, VLC, Li-Fi, Cryptography, Modified Caesar Cipher Wheel. 1. INTRODUCTION This paper is based on the concept of Li-fi. It can transmit analog as well as digital signals using LASER light as a carrier in transmitter and phototransistor as a light detector in the receiver. Here, transmitted data are encrypted by a Caesar cypher algorithm in order to ensure secured optical communication. Further, the encrypted data is decrypted on the receiver portion. Nowadays, Optical Wireless Communication (OWC) is already one of the most emerging technologies, spanning from physics, chemistry, and mathematics, electrical engineering up to architecture, psychology, and medicine [6]. In OWC infrared, visible, ultraviolet signals are used as a carrier to transfer information. OWC generally works in the bandwidth of visible region. Therefore, it can also be referred to as Visible Light Communication (VLC) [3]. Li-Fi is a subcategory of OWC, can also be a replacement of microwave communication in the context of network fidelity. Ensuring data transfer at high data rates, Li-fi has key benefits than conventional RF and microwave technology. It is wireless and uses visible light communication or infrared, which carries abundant information and solution to the RF bandwidth limitations. Spatial coherence and temporal coherence are two elementary phenomena of Lasers which permits the Laser light to travel uniformly on the narrow path and at the increased amount of speeds [3]. It has properties such as higher intensity, higher efficiency, better visibility and performance quality [4]. Typically, laser light has a much lower transmission loss per unit length (0.15-5db/km) and is not doughty to electromagnetic interference [3]. Here, on the transmitter, part modulation and optical conversion of data were implemented by the use of microcontroller and LASER. At the receiver, the phototransistor is used for optical to electrical signal conversion. Hence, another microcontroller was used to decode the different signal and the received data was given to the output. By this, a procedure has been developed for a wireless optical communication system employing Pulse Width Modulation (PWM) technique. This combines baseband or discrete