[Resource Topic] 2008/079: Homomorphic Encryption with CCA Security

Welcome to the resource topic for 2008/079

Title:
Homomorphic Encryption with CCA Security

Authors: Manoj Prabhakaran, Mike Rosulek

Abstract:

We address the problem of constructing public-key encryption schemes that meaningfully combine useful {\em computability features} with {\em non-malleability}. In particular, we investigate schemes in which anyone can change an encryption of an unknown message m into an encryption of T(m) (as a {\em feature}), for a specific set of allowed functions T, but the scheme is ``non-malleable’’ with respect to all other operations. We formulate precise definitions that capture these intuitive requirements and also show relationships among our new definitions and other more standard ones (IND-CCA, gCCA, and RCCA). We further justify our definitions by showing their equivalence to a natural formulation of security in the Universally Composable framework. We also consider extending the definitions to features which combine {\em multiple} ciphertexts, and show that a natural definition is unattainable for a useful class of features. Finally, we describe a new family of encryption schemes that satisfy our definitions for a wide variety of allowed transformations T, and which are secure under the standard Decisional Diffie-Hellman (DDH) assumption.

ePrint: https://eprint.iacr.org/2008/079

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