An Improved Modular Addition Checksum Algorithm

This paper introduces a checksum algorithm that provides a new point in the performance/complexity/effectiveness checksum tradeoff space. It has better fault detection properties than single-sum and dual-sum modular addition checksums. It is also simpler to compute efficiently than a cyclic redundancy check (CRC) due to exploiting commonly available hardware and programming language support for unsigned integer division. The key idea is to compute a single running sum, but introduce a left shift by the size (in bits) of the modulus before performing the modular reduction after each addition step. This approach provides a Hamming Distance of 3 for longer data word lengths than dual-sum approaches such as the Fletcher checksum. Moreover, it provides this capability using a single running sum that is only twice the size of the final computed check value, while providing fault detection capabilities even better than large-block variants of dual-sum approaches that require larger division operations.Comment: 9 pages, 3 figure

Monitor Based Oracles for Cyber-Physical System Testing: Practical Experience Report

Abstract—Testing Cyber-Physical Systems is becoming in-creasingly challenging as they incorporate advanced autonomy features. We investigate using an external runtime monitor as a partial test oracle to detect violations of critical system behavioral requirements on an automotive development plat-form. Despite limited source code access and using only existing network messages, we were able to monitor a hardware-in-the-loop vehicle simulator and analyze prototype vehicle log data to detect violations of high-level critical properties. Interface robustness testing was useful to further exercise the monitors. Beyond demonstrating feasibility, the experience emphasized a number of remaining research challenges, including: approxi-mating system intent based on limited system state observability, how to best balance the simplicity and expressiveness of the specification language used to define monitored properties, how to warm up monitoring of system variable state after mode change discontinuities, and managing the differences between simulation and real vehicles when conducting such tests. I