Universally composable security of identity-based signature schemes

Zecheng Wang, Zhibin Li

Dingfeng Ye

Idea Functionality is the core and basic unit of Universally Composable(UC) security protocols.The first step of designing the protocols,within the UCsecurity framework,is to extract an ideal functionality from the expected functionalities of the protocols.To appropriately define an ideal functionality we should not only protect the security of the definition,but also consider the realizability.This study investigates the security of identity-based signature(IBS) within the UCframework,defines a realizable identity-based signature functionality FIBS,proves that UC-secure IBS is equivalent to conventionally-secure(EUF-CMIA-secure) IBS.As a result,we are able to make sure that the EUFCMIA scheme can be a module in designing a complex protocol that satisfies the UCrequirement.

Zhibin Li

Since up to now the security of multi-signature protocols has only been considered in a single instance, the security of a multi-signature protocol when it is running with many other protocols concurrently was studied in the universal composable security framework. Firstly, the idea functionality of a multi-signature protocol was defined formally. Then, based on Waters' signature scheme, a multi-signature protocol was presented, which was proved to be Unified Communications (UC) secure. Thus, the presented multi-signature protocol can run safely in multi-protocol executing environments, such as Internet.

Ryo Nishimaki, Yoshifumi Manabe, Tatsuaki Okamoto

Malone-Lee, John C, Dent, AW

ZHAO Chen,YU Huifang,LI Jianmin

At present,most group signature is only secure in the standard alone.Its security becomes weak in multiple protocol environment.In view of this,the security of group signature protocol is studied in the multiple concurrent execution under the universally composable framework.Since the protocol can be analyzed modularly under the universally composable framework,an ideal function of group signature protocol is defined in this framework.Then a group signature protocol is proposed to realize the ideal function,and its universally composable security as well as unforgeability is also proved.Furthermore,a concrete instance of this universally composable group signature protocol is given.Analysis results show that this protocol security is suitable for applications in multiple concurrent environment.