Kobbi Nissim is a professor of Computer Science at Ben-Gurion University and an affiliate professor at Georgetown Law. Nissim's current work is focuses on the mathematical formulation and understanding of privacy. In this line, his work from 2003 and 2004, with Dinur and Dwork, initiated rigorous foundational research of privacy and presented a precursor of differential privacy—a strong definition of privacy in computation that he introduced in 2006 with Dwork, McSherry and Smith. With collaborators, Nissim presented some of the basic constructions supporting differential privacy, and studied differential privacy in various contexts, including statistics, computational learning, mechanism design, and social networks.

Since 2011, Kobbi has been involved with the Privacy Tools for Sharing Research Data project at Harvard, developing privacy-preserving tools for the sharing of social-science data. Other contributions of Nissim include the BGN homomorphic encryption scheme with Boneh and Goh, and the research of private approximations. In 2013, Nissim received, with Irit Dinur, the Alberto O. Mendelson Test of time award for their PODS 2003 work on privacy.