Research Of Forward-secure Digital Signature Scheme Based On Owe-way Hash Chain

It is very important to protect the security of signer's secret key in the digital signature system. In the traditional digital signatures , once the signer's secret key is exposed, then not only the security of the current digital signatures become suspect, but also the security of the signatures signed before the exposure can not be guaranted, and will cause all signatures, including those signed before the key exposure, becomes invalid inevitably. Therefore, the key exposure problem seriously threatened the security of digital signature system. How to reduce the possibility of key exposure by using cryptographic methods and how to reduce the damages to the system caused by the key exposure is very important research work that to which the researchers have paid much more attention. There have been proposed many important works about key security such as Threshold digital signature scheme, Proactive threshold digital signature scheme, Forward-secure signature scheme, Strong forward-secure signature scheme, Key-insulated signature scheme, Intrusion-resilient signature scheme etc.This paper mainly studies the forward-secure signature schemes. Compared with the traditional digital signatures, the forward-secure signature schemes can protect the security of the signatures signed before the key exposure and reduce the damages caused by the key exposure. But the forward-secure signature schemes have a fundamental limitation: unable to protect the future signatures'security after the key exposure , and cann't provide key exposure detection mechanism. This paper, based on the one-way Hash chain technology, has made the improvement to two kind of typical forward-secure signature schemes, proposed an improved forward-secure signature scheme for the first time, and addressed the problems which forward-secure digital signature schemes have confronted with. Moreover, we study and analyze the existing forward-secure proxy signature schemes, and pointed out that these schemes cann't protect the security of the proxy signatures after the proxy signer's key exposure, and unable to detect the key exposure. We proposed an improved forward-secure proxy signature scheme based on the one-way Hash chain for the first time, and addressed the security weakness of ordinary forward-secure proxy signature schemes .