Hook-in Privacy Techniques for gRPC-based Microservice Communication

TL;DR

The paper tackles privacy in gRPC-based microservice communications by introducing a gRPC-native interception framework that enforces data minimization and purpose limitation. It provides a general approach plus a Go-based prototype that uses a PAP/PDP/PEP architecture with signed JWTs to carry policy decisions, enabling per-call privacy views without invasive changes to existing services. A JSON-based policy format defines service-specific purposes and data-field handling (allowed, generalized, noised, reduced), and a lightweight interceptor enforces these decisions at response time. Preliminary experiments in a realistic food-delivery setting show that the privacy-enabled interceptor incurs measurable but practical overhead, supporting regulatory-by-design goals while preserving high-performance inter-service communication.

Abstract

gRPC is at the heart of modern distributed system architectures. Based on HTTP/2 and Protocol Buffers, it provides highly performant, standardized, and polyglot communication across loosely coupled microservices and is increasingly preferred over REST- or GraphQL-based service APIs in practice. Despite its widespread adoption, gRPC lacks any advanced privacy techniques beyond transport encryption and basic token-based authentication. Such advanced techniques are, however, increasingly important for fulfilling regulatory requirements. For instance, anonymizing or otherwise minimizing (personal) data before responding to requests, or pre-processing data based on the purpose of the access may be crucial in certain usecases. In this paper, we therefore propose a novel approach for integrating such advanced privacy techniques into the gRPC framework in a practically viable way. Specifically, we present a general approach along with a working prototype that implements privacy techniques, such as data minimization and purpose limitation, in a configurable, extensible, and gRPC-native way utilizing a gRPC interceptor. We also showcase how to integrate this contribution into a realistic example of a food delivery use case. Alongside these implementations, a preliminary performance evaluation shows practical applicability with reasonable overheads. Altogether, we present a viable solution for integrating advanced privacy techniques into real-world gRPC-based microservice architectures, thereby facilitating regulatory compliance ``by design''.

Figures (3)

• Figure 1: Architectural overview representing the communication process between client and server using JWT in gRPC communication incl. the XACML-inspired control functionality mapping.
• Figure 2: Schematic description of the gRPC interceptor.
• Figure 3: Performance overheads for 3 different message sizes and 6 degrees of operational complexity.