Feng - Hao

of “Error Tolerant Cryptography ” by Feng-Hao Liu, Ph.D., Brown University, April 2013. One of the major goals in cryptography is to design protocols that withstand malicious behavior of an adversary. Traditionally, the focus was on a setting where honest users followed their protocol exactly, without fault. But what if an adversary can induce faults, for example a physical attack that changes the state of a user’s computation, forcing a user to accept when he should be rejecting; or tries to use a modified secret key? Can any security guarantees still be given when such errors occur? My PhD work studies the implications of various types of errors and develops techniques that protect against them. I have delved into the following topics for different scenarios of errors: (1) cryptography with imperfect hardware, where the adversary can cause the cryptographic device to leak some secret information and tamper with the device’s memory; (2) secure delegation protocols, where a user can delegate some computation to an untrusted server that causes errors. To highlight some of my results: • I gave a generic construction to secure any cryptographic functionality against continual memory tampering and leakage errors in the split-state model. My main tool is to construct a non-malleable code that is also leakage resilient in this model, which resolves one central open problem in the previous work (due to Dziembowski et al. – ICS 10). • I developed new delegation protocols that allow a user, who only stores a short certificate of his data (potentially very large), to delegate the computation on the data to the cloud, and then verify the outcome in time sub-linear in the data size. In the thesis, I elaborate my work in these two lines, and some potential future directions. Error Tolerant Cryptography by Feng-Hao Liu Sc.B., National Taiwan University, 2005 Sc.M., Brown University, 2009 A dissertation submitted in partial fulfillment of the requirements for the Degree of Doctor of Philosophy in the Department of Computer Science at Brown University Providence, Rhode Island April 2013 c © Copyright 2013 by Feng-Hao Liu This dissertation by Feng-Hao Liu is accepted in its present form by the Department of Computer Science as satisfying the dissertation requirement for the degree of Doctor of Philosophy. Date Anna Lysyanskaya, Director Recommended to the Graduate Council Date John Savage, Reader Brown University Date Paul Valiant, Reader Brown University Date Yevgeniy Dodis, Reader New York University Approved by the Graduate Council Date Peter M. Weber Dean of the Graduate School