Abstract
In this paper, for the first tune in the literature, we introduce the notion of online/offline ring signature scheme Our primitive enables ring signature schemes to be used in practice, since the online mechanism can be performed very efficiently and hence, it is very suitable to be used in a mobile-device environment We provide a formal model to capture our primitive, and we proceed with a concrete construction of online/offline ring signature schemes. Finally, we show that out scheme is secure in our model