Decentagram: Highly-Available Decentralized Publish/Subscribe Systems

This paper presents Decentagram, a decentralized framework for data dissemination using the publish/subscribe messaging model. Decentagram uses blockchain smart contracts to authenticate events that will be published using digital signatures or self-attestation certificates from code running in trusted execution environments (TEEs), both of which are verified on-chain. This approach permits any host with valid credentials to publish verified updates, increasing decentralization and availability of the system as a whole by simplifying compensation and incentivization, even for untrusted hosts running TEEs. Decentagram also supports on-chain subscribers where third-party contracts receive events immediately: within the same transaction as the published event. The same event will also be delivered to off-chain subscribing applications through an off-chain event broker. We provide an open-source implementation of Decentagram, and evaluate the gas cost of its on-chain components and the end-to-end latency of its off-chain component.