Secure public-key encryption scheme without random oracles

In the real world, cryptographic computations are often performed on a relatively insecure device which can not be trusted to maintain secrecy of the secret key. Exposure of secret keys is perhaps the most debilitating attack on a cryptosystem since it implies that all security guarantees are lost. The notion of forward security guarantees that the compromise of current secret keys does not compromise past secret keys and past communications. Therefore, it can minimize the resulting damage caused by the exposure of secret keys, and provides a promising approach to deal with the secret key exposure. In this paper, we present an efficient forward-secure public-key encryption scheme and prove it to be secure in the standard model. Most of the performance parameters of our proposed scheme are independent on the total number of time periods. When compared with the previous scheme, our scheme is much more efficient.