We introduce a generic approach to constructing reusable fuzzy extractors. We define a new primitive called a \emph{reusable pseudoentropic isometry} that projects an input metric space to an output metric space. This projection preserves distance and entropy even if the same input is mapped to multiple output metric spaces. A reusable pseudoentropy isometry yields a reusable fuzzy extractor by 1) randomizing the noisy secret using the isometry and 2) applying a traditional fuzzy extractor to derive a secret key.
We propose reusable pseudoentropic isometries for the set difference and Hamming metrics. The set difference construction is built from composable digital lockers (Canetti and Dakdouk, Eurocrypt 2008) yielding the first reusable fuzzy extractor that corrects a {\it linear} fraction of errors. For the Hamming metric, we show that the second construction of Canetti \textit{et al.} (Eurocrypt 2016) can be seen as an instantiation of our framework. In both cases, the pseudoentropic isometry's reusability requires noisy secrets distributions to have entropy in each symbol of the alphabet.
Lastly, we implement our set difference solution and describe two use cases.
Category / Keywords: fuzzy extractors, reusability, reusable pseudoentropic isometry Date: received 21 Nov 2016, last revised 5 Mar 2018 Contact author: chloe cachet at gmail com Available format(s): PDF | BibTeX Citation Note: changing format Version: 20180305:121122 (All versions of this report) Short URL: ia.cr/2016/1100 Discussion forum: Show discussion | Start new discussion