Paper 2002/097

A new public key encryption scheme provably secure against adaptive chosen cipher-text attack

Huafei Zhu

Abstract

We present a new public key cryptosystem based on the notion called square decisional Diffie-Hellman problem. The scheme is provably secure against adaptive chosen cipher-text attack under the hardness assumption of the square decisional Diffie-Hellman problem. Compared with Cramer and Shoup's notable public key scheme, our scheme enjoys several nice features: (1)Both schemes are provably secure against adaptive chosen cipher-text attack under the intractability paradigm (the security of Cramer-Shoup's scheme is based on the standard decisional Diffie-Hellman problem while ours based on the square decisional Diffie-Hellman problem; (2)The computational and communication complexity of our scheme is equivalent to the Cramer and Shoup's scheme however, the test function of Cramer-shoup's scheme is linear while our scheme is non-linear, therefore our reduction is more efficient.