Paper 2014/269

Chosen Ciphertext Security via Point Obfuscation

Takahiro Matsuda and Goichiro Hanaoka

Abstract

In this paper, we show two new constructions of chosen ciphertext secure (CCA secure) public key encryption (PKE) from general assumptions. The key ingredient in our constructions is an obfuscator for point functions with multi-bit output (MBPF obfuscators, for short), that satisfies some (average-case) indistinguishability-based security, which we call AIND security, in the presence of hard-to-invert auxiliary input. Specifically, our first construction is based on a chosen plaintext secure PKE scheme and an MBPF obfuscator satisfying the AIND security in the presence of computationally hard-to-invert auxiliary input. Our second construction is based on a lossy encryption scheme and an MBPF obfuscator satisfying the AIND security in the presence of statistically hard-to-invert auxiliary input. To clarify the relative strength of AIND security, we show the relations among security notions for MBPF obfuscators, and show that AIND security with computationally (resp. statistically) hard-to-invert auxiliary input is implied by the average-case virtual black-box (resp. virtual grey-box) property with the same type of auxiliary input. Finally, we show that a lossy encryption scheme can be constructed from an obfuscator for point functions (point obfuscator) that satisfies re-randomizability and a weak form of composability in the worst-case virtual grey-box sense. This result, combined with our second generic construction and several previous results on point obfuscators and MBPF obfuscators, yields a CCA secure PKE scheme that is constructed \emph{solely} from a re-randomizable and composable point obfuscator. We believe that our results make an interesting bridge that connects CCA secure PKE and program obfuscators, two seemingly isolated but important cryptographic primitives in the area of cryptography.

Note: This is the full version of our paper in TCC 2014.

Metadata
Available format(s)
PDF
Category
Public-key cryptography
Publication info
A major revision of an IACR publication in TCC 2014
Keywords
public key encryptionlossy encryptionkey encapsulation mechanismchosen ciphertext securitypoint obfuscation.
Contact author(s)
t-matsuda @ aist go jp
History
2014-04-21: received
Short URL
https://ia.cr/2014/269
License
Creative Commons Attribution
CC BY

BibTeX

@misc{cryptoeprint:2014/269,
      author = {Takahiro Matsuda and Goichiro Hanaoka},
      title = {Chosen Ciphertext Security via Point Obfuscation},
      howpublished = {Cryptology ePrint Archive, Paper 2014/269},
      year = {2014},
      note = {\url{https://eprint.iacr.org/2014/269}},
      url = {https://eprint.iacr.org/2014/269}
}
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