## 2 Problem Definition  
The importance of data security in IoT applications is highlighted in the introduction section. Data security is important for practically every Internet-connected device. The complexity of data security implementation tasks varies greatly and depends on the application and on the industry requirement for which the device is used. For example, implementation of data security for distributed control systems with real-time constraints is considered a highly challenging task. In such systems, real-time constraints apply on the process of data security provision/implementation. Distributed systems, which are connected through various networks and/or over the Internet are susceptible to latencies in data transfer, hence data processing, such as security implementation, must be conducted within the shortest possible time in order not to impair the functionality of the system. Latency analysis is an important factor in real-time communication. The developed system measures/analyses the secure video communication latency using a number of configurations based on different hardware, encoding schemes, block sizes of encryption algorithm and transport protocols.  
A marine system, which pertains to IoVT and IoRT, used for IRM (inspection, repair and maintenance) of wind farms and other remote offshore structures, is used as the target application in this work. This system is developed by the CRIS (Centre for Robotics and Intelligent Systems) at the University of Limerick [13]. This developed system consists of a marine ROV, which is controllable remotely over the Internet and a control station. All features of the robotic system (i.e., an on-board camera, connectivity over the Internet and the lack of a security mechanism) made it a perfect platform for experiments conducted for the purpose of this work.  
The work of this paper mainly involves secure and unsecure video latency measurement over the Internet. As mentioned above, the target application is marine, which involves the remote control of an ROV from a control station. The encryption level security is implemented using a previously published AES [14] algorithm implementation on FPGA [15; 16], where AES is implemented on a traditional FPGA and then imported into LabVIEW FPGA to use with a developed LabVIEW application for video latency measurement. The AES security feature is controlled using the enable/disable option in the LabVIEW software. The structure of the target application is shown in Figure 1. It depicts the remote control station and the robot deployment location as two main components of the system. The two locations can be connected either through a LAN or through the Internet. On both ends there are dedicated stratum \(1\) NTP servers which are used as the source for precise clock synchronization. Two main applications are also shown (i.e., a visual event generator that is used for generating events, which are captured by the camera and a latency measurement application (used for calculating glass-to-glass latency). The video stream is passed through the LabVIEW application, which encrypts the data. The encryption is conducted on encoded video data. Similarly, before the decoding process takes place on the receiving end, the stream has to pass through the decryption process. The encryption and decryption process is done by the same application, and that is why the application is named as Encrypt/Decrypt.  
As mentioned previously, in this work an FPGA is used to provide AES security and the comparison of traditional FPGA and LabVIEW FPGA is given in [14].