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 achieving this enhancement.