## Cryptology ePrint Archive: Report 2013/806

(Anonymous) Compact HIBE From Standard Assumptions

Somindu C. Ramanna and Palash Sarkar

Abstract: We present two hierarchical identity-based encryption (HIBE) schemes, denoted as $\ahibe$ and $\hibe$, from Type-3 pairings with constant sized ciphertexts. Scheme $\ahibe$ is anonymous and $\hibe$ is non-anonymous. The constructions are obtained by extending the IBE scheme recently proposed by Jutla and Roy (Asiacrypt 2013). Security is based on the standard decision Symmetric eXternal Diffie-Hellman (SXDH) assumption. In terms of provable security properties, all previous constructions of constant-size ciphertext HIBE schemes had one or more of the following drawbacks: secure in the weaker model of selective-identity attacks; exponential security degradation in the depth of the HIBE; and use of non-standard assumptions. The security arguments for $\ahibe$ and $\hibe$ avoid all of these drawbacks. Along with theoretically satisfying security, the parameter sizes and efficiencies of the different algorithms of the two schemes compare very well with all previously known constructions. Based on currently known techniques, $\ahibe$ and $\hibe$ fill an important gap in the state-of-the-art on efficient (anonymous) HIBE constructions.

Category / Keywords: public-key cryptography / hierarchical identity-based encryption (HIBE), constant-size ciphertext HIBE, asymmetric pairings, standard assumptions, dual-system encryption