A Layered Secure Messaging Architecture for Cross-Organizational Manufacturing-as-a-Service

The Manufacturing-as-a-Service (MaaS) approach makes possible production services offered and utilized on an ondemand basis through organizations' boundaries. It raises issues associated with the protection of confidentiality, authentication, and integrity of exchanged information in complex, distributed systems featuring intermediating brokers. Although lightweight solutions, such as MQTT protocol, are prevalently used due to scalability and simplicity of implementation, they lack inherent mechanisms for establishing end-to-end security assurances. While transport-layer approaches, like TLS, protects individual links of the communications process, they are inadequate in multi-hop scenarios, when brokers may modify, or drop messages. In this work, we present an architecture of a secure messaging solution for the MaaS ecosystem that leverages publish/subscribe MQTT-based communication, mutual TLS transport security, token-based identity and access management, and applicationlevel encryption of message payloads. Our architecture minimizes trust requirements for brokers while retaining scalability and asynchronous characteristics. We outline our design, its security properties, and a corresponding threat model as well as describe a systematic evaluation approach to analyze latency, throughput, communication overhead, and security aspects.