A new multi-recipient tree-based signcryption scheme

Achieving both message confidentiality and message origin authenticity at a reasonable computational cost, especially in case of using smart cards with limited processing capabilities, has always been considered a challenging problem. Signcryption is one attractive cryptographic solution. An even more challenging problem is that of achieving both goals in multi-cast operations necessary for secure group communications. This paper presents a new tree-based, multi-recipient identity-based signcryption scheme. Its basic idea is to split the group members into fixed subsets, which in turn are used to cover any arbitrary subset of users thereafter. This structure reduces both the computational overhead as well as the communications overhead required in the multi-recipient case. Performance of the proposed scheme is analyzed and possible applications are suggested.