Abstract: Cloud computing is an attractive criterion for accessing virtually unlimited storage and computational resources. Cloud computing has many advantage, but providing the data confidentiality in the cloud is major concern. The major disadvantages in the cloud computing is high latency, limited mobility, slow response time because data is transferred through Multiple hops. And it is centralized Geo-distribution. In Our System, we propose the Fog computing which address the above problems faced by cloud computing. Fog computing is a criterion which extends the cloud computing and its services to the network edge. It canít replace cloud. It extends the cloud computing by providing the security in the cloud atmosphere. Fog has many advantages when compared to the cloud i.e., less data traffic, low cost and latency. It also eliminates the overhead to the centralized computing system, and security is high because data moves across the edge of the network so response is quick. Still there are many advantageous in fog computing, but some of the security issues also taken into consideration while transferring the data. In our system we focus on providing the security to the data while transferred via cloud. Here Outsourcer sends the encrypted data along generated key (cipher key/encrypted key) to the data user via Fog Server. Using that encryption key the user decryption is performed and then viewed the original data. This Cipher key is generated by the Modified ELGAMAL algorithm which provides the better security than the existing algorithm.

Keywords: Fog Computing, Cryptography, ElGamal, Cipher key.