Shrinking the Keys of Discrete-Log-Type Lossy Trapdoor Functions

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Shrinking the Keys of Discrete-Log-Type Lossy Trapdoor Functions
To this day, realizations in the standard-model of (lossy) trapdoor functions from discrete-log-type assumptions require large public key sizes, e.g., about Θ(λ2 ) group elements for a reduction from the decisional Diffie-Hellman assumption (where λ is a security parameter). We propose two realizations of lossy trapdoor functions that achieve public key size of only Θ(λ) group elements in bilinear groups, with a reduction from the decisional Bilinear Diffie-Hellman assumption. Our first construction achieves this result at the expense of a long common reference string of Θ(λ2 ) elements, albeit reusable in multiple LTDF instantiations. Our second scheme also achieves public keys of size Θ(λ), entirely in the standard model and in particular without any reference string, at the cost of a slightly more involved construction. The main technical novelty, developed for the second scheme, is a compact encoding technique for generating compressed representations of certain sequences...
Xavier Boyen, Brent Waters
Added 18 Jul 2010
Updated 18 Jul 2010
Type Conference
Year 2010
Where ACNS
Authors Xavier Boyen, Brent Waters
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