List of English Publication

@inproceedings{HaShim19,

title = {Study on Realizable Generalized Hold Functions As a Countermeasure against Zero Dynamics Attack },

author = {Jongsoo Ha and Hyungbo Shim},

doi = {https://doi.org/10.1109/CDC40024.2019.9029726},

year  = {2019},

date = {2019-12-12},

booktitle = {Proc. of 2019 IEEE 58th Conference on Decision and Control},

pages = {5362-5367},

publisher = {IEEE},

address = {Nice, France},

abstract = {Zero dynamics attacks are known to be lethal in the sense that they are stealthy in principle and are not detected from output measurements. Therefore, instead of detecting the zero dynamics attacks, an idea to mitigate the effect of the zero dynamics attack has been proposed recently, which is to enforce the zeros to become stable by changing the zero-order hold to a generalized hold in the sampled data framework. Once all the zeros become stable, then even if the zero dynamics attack is engaged, its effect on the plant is negligible. However, it was observed that the amplitude of the generalized hold becomes unrealistically large in some cases, which leads to a large input to the physical plant. This paper studies this phenomenon at a deeper level and figures out that changing the intrinsic zeros requires an excessively large amplitude of the generalized hold while changing the sampling zeros can be done with a reasonable amplitude.},

keywords = {Generalized hold, Zero-dynamics},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{KimShim19,

title = {A Countermeasure against Zero-dynamics Sensor Attack via Generalized Hold Feedback},

author = {Jihan Kim and Hyungbo Shim},

doi = {https://doi.org/10.23919/SICE.2019.8859930},

year  = {2019},

date = {2019-09-12},

booktitle = {Proc. of the SICE Annual Conference 2019},

pages = {663-668},

publisher = {SICE},

address = {Hiroshima, Japan},

abstract = {The zero-dynamics attack is well-known for its lethality and stealthiness. This infamous attack has usually been studied as a type of actuator attack. In this paper, however, we focus on the zero-dynamics attack having a form of a sensor attack. In particular, when the system monitors abnormal behavior of the plant using the anomaly detector, an undetectable sensor attack can be generated, which deceives the anomaly detector. It is noticed that this sensor attack is not so effective when the plant is stable even if the attack is still undetectable. In view of this point, we propose to reexamine the so-called ‘generalized hold’ as a countermeasure against the undetectable sensor attack. Specifically, using the fact that the output feedback composed of the ‘generalized hold’ can stabilize the unstable systems by selecting an appropriate hold function, we show that the plant can be safe from the undetectable sensor attack.},

keywords = {Cyber-physical system, Generalized hold, Resilient control system, Sampled-data control system},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{BackKimLeeParkShim17,

title = {Enhancement of Security against Zero Dynamics Attack via Generalized Hold},

author = {Juhoon Back and Jihan Kim and Chanhwa Lee and Gyunghoon Park and Hyungbo Shim},

doi = {10.1109/CDC.2017.8263842},

year  = {2017},

date = {2017-12-11},

booktitle = {Proc. of IEEE Conf. on Decision and Control},

pages = {1350-1355},

address = {Melbourne, Australia},

abstract = {Zero dynamics attack is lethal to cyber-physical systems in the sense that it is stealthy and there is no way to detect it. Fortunately, if the given continuous-time physical system is of minimum phase, the effect of the attack is negligible even if it is not detected. However, the situation becomes unfavorable again if one uses digital control by sampling the sensor measurement and using the zero-order-hold for actuation because of the `sampling zeros.' When the continuous-time system has relative degree greater than two and the sampling period is small, the sampled-data system must have unstable zeros (even if the continuous-time system is of minimum phase), so that the cyber-physical system becomes vulnerable to `sampling zero dynamics attack.' In this paper, we begin with its demonstration by a few examples. Then, we present an idea to protect the system by allocating those discrete-time zeros into stable ones. This idea is realized by employing the so-called `generalized hold' which replaces the zero-order-hold.},

keywords = {Generalized hold},

pubstate = {published},

tppubtype = {inproceedings}

}