Cryptology ePrint Archive: Report 2008/278

An Improved Robust Fuzzy Extractor

Bhavana Kanukurthi and Leonid Reyzin

Abstract: We consider the problem of building robust fuzzy extractors, which allow two parties holding similar random variables W, W' to agree on a secret key R in the presence of an active adversary. Robust fuzzy extractors were defined by Dodis et al. in Crypto 2006 to be noninteractive, i.e., only one message P, which can be modified by an unbounded adversary, can pass from one party to the other. This allows them to be used by a single party at different points in time (e.g., for key recovery or biometric authentication), but also presents an additional challenge: what if R is used, and thus possibly observed by the adversary, before the adversary has a chance to modify P. Fuzzy extractors secure against such a strong attack are called post-application robust.

We construct a fuzzy extractor with post-application robustness that extracts a shared secret key of up to (2m-n)/2 bits (depending on error-tolerance and security parameters), where n is the bit-length and m is the entropy of W. The previously best known result, also of Dodis et al., extracted up to (2m-n)/3 bits (depending on the same parameters).

Category / Keywords: applications / Robust Fuzzy Extractors, Privacy Amplification, Information Reconciliation

Publication Info: This is a pre-print of the SCN 2008 paper

Date: received 19 Jun 2008, last revised 24 Jul 2008

Contact author: bhavanak at bu edu

Available format(s): Postscript (PS) | Compressed Postscript (PS.GZ) | PDF | BibTeX Citation

Version: 20080724:191644 (All versions of this report)

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