Chosen-ciphertext secure proxy re-encryption

  • Authors:
  • Ran Canetti;Susan Hohenberger

  • Affiliations:
  • IBM T. J. Watson Research Center, Hawthorne, NY;Johns Hopkins University, Baltimore, MD

  • Venue:
  • Proceedings of the 14th ACM conference on Computer and communications security
  • Year:
  • 2007

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Abstract

In a proxy re-encryption (PRE) scheme, a proxy is given special information that allows it to translate a ciphertext under one key into a ciphertext of the same message under a different key. The proxy cannot, however, learn anything about the messages encrypted under either key. PRE schemes have many practical applications, including distributed storage, email, and DRM. Previously proposed re-encryption schemes achieved only semantic security; in contrast, applications often require security against chosen ciphertext attacks. We propose a definition of security against chosen ciphertext attacks for PRE schemes, and present a scheme that satisfies the definition. Our construction is efficient and based only on the Decisional Bilinear Diffie-Hellman assumption in the standard model. We also formally capture CCA security for PRE schemes via both a game-based definition and simulation-based definitions that guarantee universally composable security. We note that, simultaneously with our work, Green and Ateniese proposed a CCA-secure PRE, discussed herein.