IACR News item: 19 March 2015
Keita Xagawa
ePrint ReportWe address this efficiency issue by ``untwisting\'\' their twist and providing another twist. Our scheme supports inner-product predicates over $R^\\mu$ where $R = \\mathrm{GF}(q^n)$ instead of $\\mathbb{Z}_q$. Our scheme has public parameters of size $O(\\mu n^2 \\lg^2{q})$ and ciphertexts of size $O(\\mu n \\lg^2{q})$. Since the cardinality of $\\mathrm{GF}(q^n)$ is inherently exponential in $n$, we have no need to set $q$ as the exponential size for applications.
As side contributions, we extend our IPE scheme to a hierarchical IPE (HIPE) scheme and propose a fuzzy IBE scheme from IPE. Our HIPE scheme is more efficient than that developed by Abdalla, De Caro, and Mochetti (Latincrypt 2012). Our fuzzy IBE is secure under a much weaker assumption than that employed by Agrawal et al.~(PKC 2012), who constructed the first lattice-based fuzzy IBE scheme.
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