# Secure and Privacy-Respecting Documentation for Interactive Manufacturing and Quality Assurance
## 2 Basic System Architecture  
Since the challenge of adequate data privacy protection in smart manufacturing systems is still largely unsolved, our goal in this work is to develop mechanisms for protecting the privacy and informational self-determination of workers subjected to these types of assistance systems. More concretely, we base our contribution on an existing collaborative manual assembly station, which is fitted with a multitude of sensors to monitor, supervise and individually assist the worker [2]. We extend this system with suitable privacy-protection components and integrate our solution into the physical assembly station as a proof-of-concept implementation. Nevertheless, our findings are generally applicable for any assistance systems that capture and store video footage of workers. In this section, we briefly describe the existing assembly station and extract a basic system design for it. Afterwards we describe how the assembly station can be extended with components to automatically detect and document critical work steps as video footage. Based on this abstract system design, we later derive data protection and data security requirements (Section 3) and develop advanced security mechanisms (Section 4). Figure 1 shows the assembly station [2] we use as a development platform to implement our privacy-protection system. The assembly station is fitted with a set of stereo cameras for tool tracking purposes and a depth-camera for detecting the worker. Furthermore, it features a projector that can present information and instructions about the current work step directly on the work piece. When the worker begins his task, the assembly station captures a live video stream from the depth camera, which provides both a video and a 3D point cloud. The assistance system uses the image data stream to automatically detect the currently executed work step and compares it to a domain-specific workflow model. Then the worker can be assisted by projecting information for this work step directly on the work piece. This manual assembly scenario is convenient for our purpose due to its relative simplicity and self-containment. Since all components shown in Figure 1 operate locally on a single computer, no network connections must be considered. From a data protection perspective, the aim is to implement as much system functionality as possible without having to store personal data. At the same time, there is a need to collect data to a certain extent for quality assurance and optimization purposes. Our goal is to extend this assistance system with the secure storage and retrieval of critical work data, without impeding the informational self-determination of assisted workers. As a first step, we extend the assembly station shown in Figure 1 with the capability of retaining videos of critical work procedures for documentation purposes. This can be done by integrating a video storage component with the existing workflow detection. If a critical work step is detected, a personalized workflow log and a personalized video snippet are generated and persisted on the hard drive. Due to possible delays caused by the detection component, a ring buffer is introduced to ensure that the first few seconds of such work steps are not missed. Furthermore, the captured documentation should be linked to the user's identity for later review. For this, we mount a smartcard reader near the assembly station, which the worker uses to authenticate and log in at the system before beginning his task. To be able to view the recorded data in case of an inspection, e.g., due to a problem with one of the workpieces, the system must also offer the possibility to retrieve and display the recorded work steps and workflow logs. For simplicity purposes, this is done by placing a monitor next to the assembly station that shows the recorded videos to supervisors. An overview of the resulting system architecture including the described modifications is given in Figure 2. The documentation system consists of three components.