Finding Compact Reliable Broadcast in Unknown Fixed-Identity Networks (Short Paper)

At PODC'05, Subramanian, Katz, Roth, Shenker and Stoica (SKRSS) introduced and formulated a new theoretical problem called reliable broadcast problems in unknown fixed-identity networks [3] and further proposed a feasible result to this problem. Since the size of signatures of a message traversing a path grows linearly with the number of hops in their implementations, this leaves an interesting research problem (an open problem advertised by Subramanian et al in [3]) – how to reduce the communication complexity of their reliable broadcast protocol? In this paper, we provide a novel implementation of reliable broadcast problems in unknown fixed-identity networks with lower communication complexity. The idea behind of our improvement is that we first transfer the notion of path-vector signatures to that of sequential aggregate path-vector signatures and show that the notion of sequential aggregate path-vector is a special case of the notion of sequential aggregate signatures. As a result, the currently known results regarding sequential aggregate signatures can be used to solve the open problem. We then describe the work of [3] in light of sequential aggregate signatures working over independent RSA, and show that if the size of an node vi,j's public key |g(vi,j)| is ti,j and the number of hops in a path pi is di in the unknown fixed-identity graph G (with k adversaries), the reduced communication complexity is approximate to while the computation (time) complexity of our protocol is the same as that presented in [3].