Metric Pseudoentropy: Characterizations, Transformations and Applications

  • Maciej SkorskiEmail author
Part of the Lecture Notes in Computer Science book series (LNCS, volume 9063)


Metric entropy is a computational variant of entropy, often used as a convenient substitute of HILL Entropy which is the standard notion of entropy in many cryptographic applications, like leakage-resilient cryptography, deterministic encryption or memory delegation. In this paper we develop a general method to characterize metric-type computational variants of entropy, in a way depending only on properties of a chosen class of test functions (adversaries). As a consequence, we obtain a nice and elegant geometric interpretation of metric entropy. We apply these characterizations to simplify and modularize proofs of some important results, in particular: (a) computational dense model theorem (FOCS’08), (b) a variant of the Leftover Hash Lemma with improvements for square-friendly applications (CRYPTO’11) and (c) equivalence between unpredictability entropy and HILL entropy over small domains (STOC’12). We also give a new tight transformation between HILL and metric pseudoentropy, which implies the dense model theorem with best possible parameters.


Side Information Linear Threshold Cryptographic Application Fuzzy Extractor Deterministic Circuit 
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© Springer International Publishing Switzerland 2015

Authors and Affiliations

  1. 1.Cryptology and Data Security GroupUniversity of WarsawWarsawPoland

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