Selective opening chosen ciphertext security directly from the DDH assumption

Abstract

Chosen-ciphertext security has been well-accepted as a standard security notion for public key encryption. But in a multi-user surrounding, it may not be sufficient, since the adversary may corrupt some users to get the random coins as well as the plaintexts used to generate ciphertexts. The attack is named "selective opening attack". We study how to achieve full-fledged chosen-ciphertext security in selective opening setting directly from the DDH assumption. Our construction is free of chameleon hashing, since tags are created for encryptions in a flexible way to serve the security proof. © 2012 Springer-Verlag.