A Note on an Encryption Scheme of Kurosawa and Desmedt
Rosario Gennaro, Victor Shoup · 2004
Recently, Kurosawa and Desmedt presented a new hybrid encryption scheme which is secure against adaptive chosen-ciphertext attack. Their scheme is a modification of the Cramer-Shoup encryption scheme. Its major advantage with respect to Cramer-Shoup is that it saves the computation of one exponentiation and produces shorter ciphertexts. However, the proof presented by Kurosawa and Desmedt relies on the use of information-theoretic key derivation and message authentication functions. In this note we present a different proof of security which shows that the Kurosawa-Desmedt scheme can be instantiated with any computationally secure key derivation and message authentication functions, thus extending the applicability of their paradigm, and improving its efficiency. 1