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Constant-rate Non-malleable Codes and their Applications

Series: Ph.D (Engg.) - Thesis Defence (Skype)

Speaker: Ms. Sai Lakshmi Bhavana ObbattuPh.D (Engg.) Dept. of CSA

Date/Time: May 29 15:30:00

Location: Skype

Faculty Advisor: Dr. Bhavana Kanukurthi

Non-malleable codes (NMCs) introduced by Dziembowski, Pietrzak and Wichs in ITCS 2010, provide powerful security guarantees where standard error-correcting codes can not provide any guarantee: a decoded message is either the same or completely independent of the underlying message. NMCs have found applications to various aspects of cryptography such as CCA secure encryption, tamper and leakage resilient cryptography, non-malleable commitments, non-malleable secret sharing schemes and so on.

In this talk, we present an application of NMCs to the fascinating problem of NMCs to the fascinating problem of Privacy Amplification. In the problem of privacy amplification, two parties, Alice and Bob, who a-priori share a weak secret, to agree on a uniform secret key, in the presence of a computationally unbounded adversary Eve. Building privacy amplification protocols with constant entropy loss and constant round complexity was open since 1988 (and recently closed in an independent work of Li [CCC 19]). In this talk, we will show how to construct such a privacy amplification protocol under the existence of non-malleable code with certain strong security guarantees. Next, we will also discuss the first explicit construction of a constant rate, constant state non-malleable code.

This talk is based on joint works with Eshan Chattopadhyay, Bhavana Kanukurthi and Sruthi Sekar.

References: [1] Bhavana Kanukurthi, Sai Lakshmi Bhavana Obbattu, and Sruthi Sekar. Four-state non-malleable codes with explicit constant rate. In Theory of Cryptography Conference, TCC 2017. Invited to Journal of Cryptology.
[2] Eshan Chattopadhyay, Bhavana Kanukurthi, Sai Lakshmi Bhavana Obbattu, and Sruthi Sekar. Privacy amplification from non-malleable codes. In Indocrypt 2019.

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