- We obtain (almost) tightly secure IBE in the multi-challenge, multi-instance setting, both in composite and prime-order groups. The latter resolves the open problem posed by Hofheinz et al (PKC '15).
- We obtain the first (almost) tightly secure IBE with sub-linear size public parameters (master public keys). In particular, we can set the size of the public parameters to constant at the cost of longer ciphertexts. This gives a partial solution to the open problem posed by Chen and Wee (Crypto '13).
By applying (a variant of) the Canetti-Halevi-Katz transformation to our schemes, we obtain several CCA-secure PKE schemes with tight security in the multi-challenge, multi-instance setting. One of our schemes achieves very small ciphertext overhead, consisting of less than 12 group elements. This significantly improves the state-of-the-art construction by Libert et al.~(in ePrint Archive) which requires 47 group elements. Furthermore, by modifying one of our IBE schemes obtained above, we can make it anonymous. This gives the first anonymous IBE whose security is almost tightly shown in the multi-challenge setting.Category / Keywords: public-key cryptography / Date: received 9 Jun 2015, last revised 9 Jun 2015 Contact author: yamada-shota at aist go jp Available format(s): PDF | BibTeX Citation Version: 20150617:002310 (All versions of this report) Short URL: ia.cr/2015/566 Discussion forum: Show discussion | Start new discussion