Michel Abdalla, Mihir Bellare, and
Gregory Neven. In D. Micciancio, editor, 7th Theory of Cryptography
Conference - TCC 2010, volume 5978 of Lecture Notes in Computer
Science, pages 480-497. Springer-Verlag, 2010.
Abstract: We provide a provable-security treatment of "robust" encryption. Robustness means it is hard to produce a ciphertext that is valid for two different users. Robustness makes explicit a property that has been implicitly assumed in the past. We argue that it is an essential conjunct of anonymous encryption. We show that natural anonymity-preserving ways to achieve it, such as adding recipient identification information before encrypting, fail. We provide transforms that do achieve it, efficiently and provably. We assess the robustness of specific encryption schemes in the literature, providing simple patches for some that lack the property. We present various applications. Our work enables safer and simpler use of encryption.