Efficient certificate-based encryption in the standard model

In this paper, we propose a new Certificate-Based Encryption (CBE) scheme which is fully secure in the standard model. We achieve chosen ciphertext (CCA) security directly without any transformation. When compared to all previous generic constructions (in either random oracle or standard model), our scheme is far more efficient than those schemes. When compared to the CBE scheme in [16] (which is the only concrete implementation secure in the standard model), we enjoy a great improvement in terms of space efficiency. Their scheme requires more than 160 group elements for the public parameters in order to gain an acceptable security. Our scheme just requires 5 group elements. In addition, the message space of our scheme is almost double as the one in [16]. A larger message space implies that it requires a smaller number of encryption operations of the same plaintext, resulting in a smaller overall ciphertext and overhead as well.