Design and Analysis of Practical Public-Key Encryption Schemes Secure against Adaptive Chosen Ciphertext Attack

A new public key encryption scheme, along with several variants, is proposed and analyzed. The scheme and its variants are quite practical, and are proved secure against adaptive chosen ciphertext attack under standard intractability assumptions. These appear to be the first publickey encryption schemes in the literature that are simultaneously practical and provably secure. This paper is a significantly revised and extended version of the extended abstract “A practical public key cryptosystem provably secure against adaptive chosen ciphertext attack” [R. Cramer and V. Shoup, in Advances in Cryptology – Crypto ’98], and also includes results originally presented in the extended abstract “Using hash functions as a hedge against chosen ciphertext attack” [V. Shoup, in Advances in Cryptology – Eurocrypt 2000].