An information flow control model in a topic-based publish/subscribe system

Abstract

A publish/subscribe (PS) model is an event-driven model of a distributed system. In traditional PS systems, each peer (process) can either publish or subscribe events. In this paper, we consider a peer-to-peer (P2P) type of topic-based PS model where each peer can both publish and subscribe events. In this paper, we newly propose a topic-based access control (TBAC) model for topic-based PS systems. Here, an access right is a pair $⟨\mathit{t}\mathrm{,}\mathit{op}⟩$ of a topic t and a publish or subscribe operation $\mathit{op}$ . A peer is allowed to publish an event message with publication topics and subscribe interesting topics only if the publication and subscription access rights are granted to the peer, respectively. An event message e is delivered to a peer ${\mathit{p}}_{\mathit{i}}$ if the publication of e and subscription of ${\mathit{p}}_{\mathit{i}}$ include some common topic. If a peer ${\mathit{p}}_{\mathit{i}}$ publishes an event message ${\mathit{e}}_2$ after receiving an event message ${\mathit{e}}_1$ , the event message ${\mathit{e}}_2$ may bring some information of the event message ${\mathit{e}}_1$ . If a target peer ${\mathit{p}}_{\mathit{j}}$ is not allowed to subscribe at least one topic which is related with the event message ${\mathit{e}}_1$ , information in the peer ${\mathit{p}}_{\mathit{i}}$ illegally flows to the target peer ${\mathit{p}}_{\mathit{j}}$ . We newly propose a subscription-based synchronization (SBS) protocol to prevent illegal information flow. Here, an event message is banned by a target peer if the event message implies illegal information flow. However, event messages may be unnecessarily banned by a peer even if no illegal information flow to the peer occurs. In the evaluation, we show the number of event messages unnecessarily banned in the SBS protocol.