Cloud computing is an amazing technology above all other types of computing. Cloud computing implies sharing of computing resources rather than having local servers or personal individual devices to handle the applications. The goal of cloud computing is to increase the speed of computations per second by applying traditional supercomputing, or high-performance computing power. It is used in consumer-oriented applications such as recruitments, smart staffing and medical image retrieval etc. The cloud computing however, has some problems associated with it . Among them security and privacy are the main concerns. This paper focus on both security and privacy issues of cloud computing. In this paper we have proposed to use Rijndael algorithm for encryption of data on the fly to provide data security in cloud . We have also proposed to make use of digital signature to ensure privacy and authentication of client's data

1. http://en. wikipedia. org/wiki/Digital_signature
2. Farzad Sabahi, presented "Cloud computing security threats and responses" at Communication Software and Networks (ICCSN), 2011 IEEE 3rd International Conference
3. Jianfeng Yang and Zhibin Chen presented "Cloud Computing Research and Security Issues", at Computational Intelligence and Software Engineering (CiSE), 2010 International Conference.
4. Rich Maggiani, solari communication. "Cloud computing is changing how we communicate".
5. N. Mead, et ai, prepared "Security quality requirements Engineering (SQUARE) methodolgy," at Carnegie Mellon Software Engineering Institute.
6. J. W. Rittinghouse and J. F. Ransome, Cloud Computing: Taylor and Francis Group, LLC, 2010.
7. www. efgh. com/software/rijndael. htm

Rijndael Algorithm Digital Signature Encryption