|Privacy is increasingly important in the online world. Corporations, governments, and other organizations are realizing and exploiting their power to track users and their behavior. On the other hand, advances in hardware technology have lead to an increase in the capability to store and record personal data about consumers and individuals. This has lead to concerns that the personal data may be misused for a variety of purposes. In order to alleviate these concerns, I study the different aspects of privacy-preserving technologies. Privacy breach may take place with or without a user's explicit participation. I am interested in both the issues. Besides the privacy of the users, my research tries to find out efficient scheme which also deals with the cost issue. I am also studying on bridging the gap between game theory and cryptography.