Sherman S.M. Chow
New York University

Practical Identity-Based Encryption Without Random Oracles

We present an Identity Based Encryption (IBE) system that is fully secure
in the standard model and has several advantages over previous such
systems namely, computational efficiency, shorter public parameters, and a
"tight" security reduction, albeit to a stronger assumption that depends
on the number of private key generation queries made by the adversary. Our
assumption is a variant of Boneh et al.'s decisional Bilinear
Diffie-Hellman Exponent assumption, which has been used to construct
efficient hierarchical IBE and broadcast encryption systems. The
construction is remarkably simple. It also provides recipient anonymity
automatically, providing a second (and more efficient) solution to the
problem of achieving anonymous IBE without random oracles. Finally, our
proof of CCA2 security, which has more in common with the security proof
for the Cramer-Shoup encryption scheme than with security proofs for other
IBE systems, may be of independent interest.

Author : Craig Gentry (Stanford University)