New forward-secure public-key encryption without random oracles

Abstract

Forward-secure public-key cryptography is an important technique for protecting private keys. It provides the benefits of frequent updating private keys without changing public keys. The most attractive property of forward security is that even if an attacker obtains the private key for the current time period, she still cannot compromise the private keys for the past time. In this paper, we newly present a forward-secure public-key encryption scheme without random oracles and prove it to be chosen-ciphertext secure in the standard model. In the proposed scheme, the ciphertext size and the decryption time have no correlation with the number of time periods and other performance indices have at most poly logarithmic complexities in terms of the number of time periods. As far as we know, it is the first forward-secure public-key encryption scheme that achieves direct chosen-ciphertext security in the standard model.

Keywords:

• public-key cryptography
• private key exposure
• forward security
• chosen-ciphertext security
• standard model

2010 AMS Subject Classifications:

• 94A60
• 68P25

1998 ACM Computing Classification System Codes:

• E.3
• K.6.5

Acknowledgements

We would like to thank the anonymous referees for their helpful comments. This work is supported by the National Natural Science Foundation of China (grant number 61272542).