An efficient public key cryptosystem secure against chosen ciphertext attack

Devising public key cryptosystems that are secure against chosen ciphertext attacks has been the subject of investigation by many researchers. However, there are actually very few secure and efficient systems in the literature. In this paper, we introduce a secure and efficient public key cryptosystem. The main advantage of our schemes is that we employ a problem equivalent to the well-studied RSA problem, and thus our schemes do not rely on conjectures or unproven claims. Therefore, the resulting schemes are as secure as the RSA system.