We are fortunate to have had Dr. Rafail Ostrovsky, Professor of Computer Science and Mathematics at UCLA, present a talk on "Cloud Security: Threats, Challenges and Solutions" today at Yahoo for our #BigThinkers series. Professor Ostrovsky discussed the importance of cryptography and some of the many capabilities of the scientific discipline in cloud security. In his talk, Ostrovsky gave examples of how traditional encryption of data in the cloud can be breached. He then followed by offering recent techniques for boosting security and enabling new functionalities. The event was broadcast live on our labs.yahoo.com homepage and viewers had the opportunity to ask questions and comment on our Twitter stream @YahooLabs as well as our Facebook page. You can view Dr. Ostrovsky's full presentation here: ABSTRACT In this talk, I will survey a number of efficient cryptographic techniques that can increase user privacy when storing and actively utilizing data in the cloud. I will first describe multiple vulnerabilities that exist (and are not protected by standard use of encryption and authentication mechanisms), which pose a real security threat when storing sensitive data into the cloud. I will then describe several techniques that allow one to minimize risk of data loss by malicious adversaries, including insider threats. These techniques are based on several advances in cryptography that make theoretical results practical. I will also mention several applications of these techniques to real-life scenarios. The talk will be self-contained and accessible to the general audience. BIOGRAPHICAL NOTE Rafail Ostrovsky is a Professor of Computer Science and Professor of Mathematics at UCLA. Dr. Ostrovsky received his Ph.D. in computer science from MIT in 1992, in the Theory of Computation Group (advisor: Silvio Micali, thesis: Software Protection). Prof. Ostrovsky's research centers on various issues in theoretical computer science, including cryptography, distributed network algorithms, and high-dimensional search problems. Prof. Ostrovsky is a Fellow of the International Association of Cryptologic Research (IACR); he has 10 U.S. patents issued and over 200 papers published in refereed journals and conferences. Dr. Ostrovsky currently serves as Vice-Chair of the IEEE Technical Committee on Mathematical Foundations of Computing and has served on 38 international conference Program Committees including serving as a PC chair of FOCS 2011. He is a member of the Editorial Board of JACM, the Editorial Board of Algorithmica; and the Editorial Board of Journal of Cryptology; he serves on the Editorial and Advisory Board of the International Journal of Information and Computer Security and is a member of the steering committee of the international symposium of Security in Communication Networks (SCN). Dr. Ostrovsky was invited (among only a few academics) to participate in U.S. Air Force Third Annual National Security Scholars Conference in 2011. Dr. Ostrovsky was invited to be the Plenary Speaker at a conference organized by the FBI in 2009, and was invited to be the Plenary Keynote Speaker for Public Key Cryptography International Conference in 2007. Dr. Ostrovsky's awards include: the Best Paper Award of the 2008 International Conference on Computing and Combinatorics (COCOON-2008); 2006 and 2005 Xerox Corporate Innovation Faculty Awards; 2006 IBM Faculty Award; 2006 Xerox Corporation Distinguished Lecture Series; 2005 Distinguished Cryptographer of the Year Lecture Series NTT Labs, Japan; OKAWA Foundation 2004 Research Award; three SAIC Awards for the best published work of the year (1999, 2001, 2002) in computer science and mathematics; the 1996 Bellcore Prize for excellence in research; 1993 Henry Taub Prize; and multiple papers solicited to journal special issues dedicated to highest PC-ranked STOC/FOCS articles. At UCLA, Prof. Ostrovsky heads the security and cryptography multi-disciplinary Research Center (http://www.cs.ucla.edu/security/) at Henry Samueli School of Engineering and Applied Science. YAHOO LABS BIG THINKERS SPEAKER SERIES Yahoo Labs is proud to bring you its 2014 Big Thinkers Speaker Series. Each year, some of the most influential, accomplished experts from the research community visit our campus to share their insights on topics that are significant to Yahoo. These distinctive speakers are shaping the future of the new sciences underlying the Web and are guaranteed to inform, enlighten, and inspire.