Publications - Abstracts

Research Group of Prof.C.P.Schnorr, University of Frankfurt am Main

Pseudorandom Function Tribe Ensembles Based on One-Way Permutations: Improvements and Applications

Marc Fischlin
Fachbereich Mathematik (AG 7.2)
Johann Wolfgang Goethe-Universität Frankfurt am Main
PSF 111932
60054 Frankfurt/Main, Germany

e-mail: marc@mi.informatik.uni-frankfurt.de
URL: http://www.mi.informatik.uni-frankfurt.de

Pseudorandom function tribe ensembles are pseudorandom function ensembles that have an additional collision resistance property: almost all functions have disjoint ranges. We present an alternative to the construction of pseudorandom function tribe ensembles based on one-way permutations given by Canetti, Micciancio and Reingold [CMR98]. Our approach yields two different but related solutions: One construction is somewhat theoretic, but conceptually simple and therefore gives an easier proof that one-way permutations suffice to construct pseudorandom function tribe ensembles. The other, slightly more complicated solution provides a practical construction; it starts with an arbitrary pseudorandom function ensemble and assimilates the one-way permutation to this ensemble. Therefore, the second solution inherits important characteristics of the underlying pseudorandom function ensemble: it is almost as efficient and if the starting pseudorandom function ensemble is efficiently invertible (given the secret key) then so is the derived tribe ensemble. We also show that the latter solution yields so-called committing private-key encryption schemes. i.e., where each ciphertext corresponds to exactly one plaintext - independently of the choice of the secret key or the random bits used in the encryption process.

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