Cryptology ePrint Archive: Report 2007/119

Rerandomizable RCCA Encryption

Manoj Prabhakaran and Mike Rosulek

Abstract: We give the first perfectly rerandomizable, Replayable-CCA (RCCA) secure encryption scheme, positively answering an open problem of Canetti et al. [CRYPTO 2003]. Our encryption scheme, which we call the Double-strand Cramer-Shoup scheme, is a non-trivial extension of the popular Cramer-Shoup encryption. Its security is based on the standard DDH assumption. To justify our definitions, we define a powerful "Replayable Message Posting" functionality in the Universally Composable (UC) framework, and show that any encryption scheme that satisfies our definitions of rerandomizability and RCCA security is a UC-secure implementation of this functionality. Finally, we enhance the notion of rerandomizable RCCA security by adding a receiver-anonymity (or key-privacy) requirement, and show that it results in a correspondingly enhanced UC functionality. We leave open the problem of constructing a scheme that achieves this enhancement.

Category / Keywords: public-key cryptography / Anonymous Rerandomizable Replayable-CCA2 Encryption Public-Key

Publication Info: To appear in CRYPTO 2007

Date: received 1 Apr 2007, last revised 16 Aug 2007

Contact author: mmp at cs uiuc edu

Available format(s): PDF | BibTeX Citation

Note: Updated version includes an improved construction for the main encryption scheme

Version: 20070817:025243 (All versions of this report)

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