Five-College Speaker Series on Information Assurance
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Tal Malkin |
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Traditionally, secure cryptographic algorithms provide security against an adversary who has only black-box access to the secret information of honest parties. However, such models are not always adequate. In particular, the security of these algorithms may completely break under (feasible) attacks that tamper with the secret key. We propose a theoretical framework to investigate the algorithmic aspects related to tamper-proof security. In particular, we define a model of security against an adversary who is allowed to apply arbitrary feasible functions f to the secret key sk, and obtain the result of the cryptographic algorithms using the new secret key f(sk). We prove that in the most general setting it is impossible to achieve this strong notion of security. We then show minimal additions to the model, which are needed in order to obtain provable security. We prove that these additions are necessary and also sufficient for most common cryptographic primitives, such as encryption and signature schemes. We also consider restrictions of the model in which the tampering powers of the adversary are limited. These restrictions model realistic attacks (like differential fault analysis) that have been demonstrated in practice. In these settings we show security solutions that work even without the additions mentioned above. Finally, if time permits, we will shift our focus to side-channel attacks, which try to obtain secret information leaked during computation (rather than tampering with its content). We propose an information theoretic framework for the analysis and design of cryptographic implementations (such as block ciphers) secure against such attacks. The talk is mostly based on joint work with Rosario Gennaro, Anna Lysyanskaya, Silvio Micali, and Tal Rabin, and depending on time, will touch upon further joint work with Francois Standaert and Moti Yung. Biography: Tal is a member of the Theory Group in the Department of Computer Science at Columbia University since January 2003. Previously, Tal was with the Secure Systems Research Department at AT&T Labs - Research. Before that, Tal was a Ph.D. student in theTheory of Computation Group and its Cryptography and Information Security Group in the Laboratory for Computer Science at MIT, and received her Ph.D. in February 2000. | |