Secret Sharing in Pub/Sub Using Trusted Execution Environments

An essential security concern in the publish/subscribe paradigm is that of guaranteeing the confidentiality of the data being transmitted. Existing solutions require that some initial parameters, keys or secrets be exchanged or otherwise established between communicating entities before secure end-to-end communication can occur. Most existing solutions in the literature either weaken the desirable decoupling properties of pub/sub or rely on a completely trusted out-of-band service to disseminate these values. This problem can be avoided through the use of Shamir's secret sharing scheme, at the cost of a prohibitively large number of messages, scaling exponentially with the path length between publisher and subscriber. Intel's Software Guard Extensions (SGX) offers trusted execution environments to shield application data from untrusted software running at a higher privilege level. Unfortunately, SGX requires the use of Intel's proprietary hardware and architecture. We mitigate these problems through HyShare, a hybrid broker network used for the purposes of sharing a secret between communicating publishers and subscribers. The broker network is composed of regular brokers that use Shamir's secret sharing scheme and brokers with SGX to reduce the overall number of messages needed to share a secret. By fine tuning the combination of these brokers, it is possible to strike a balance between network resource use and hardware heterogeneity.