Dr. Fei Hu { fei@eng.ua.edu }

Department of Electrical and Computer EngineeringUniversity of AlabamaTuscaloosa, Alabama

Introduction to CPS Security

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MotivationMotivation

"Cyber-Physical Systems (CPS) is a critical part of the national "Cyber-Physical Systems (CPS) is a critical part of the national cyber infrastructure. cyber infrastructure. SecuritySecurity threats to CPS pose significant risk threats to CPS pose significant risk to the health and safety of human lives, threaten severe damage to the health and safety of human lives, threaten severe damage to the environment, and could impose an adverse impact on the to the environment, and could impose an adverse impact on the U.S. economy." U.S. economy."

- - Homeland Security, Dr. Nabil Adam, 2010Homeland Security, Dr. Nabil Adam, 2010. .

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CPS Security: What?CPS Security: What?

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Implantable devices

cyber objects

Smart grid

Sensors

Actuators

computing (HW/SW)

Physical objects

IMD

App 1: Healthcare

App 2: Renewable Energy

App 3: Industrial Control

Cyber-physical Interaction security

Physical → Cyber: Monitoring Security • Sensor data attacks • RFID tag attacks

• Memory reading attacks • Log attacks (forensics)

Cyber → Physical: Control Security

• Wireless charge attacks; • Close-loop control attacks; • Device coordination attack; • Command misleading, etc.

Fig.2 Cyber-Physical Systems (CPS): Security Perspective

CPS Security: Why?CPS Security: Why?

Cannot simply use conventional, Cannot simply use conventional, general cyber security schemes to general cyber security schemes to achieve all CPS protections. achieve all CPS protections.

This is because most CPS security This is because most CPS security solutions need to be closely solutions need to be closely integrated with the underlying integrated with the underlying physical process control features. physical process control features.

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CPS Security: ExampleCPS Security: Example

IMD Wireless Powering securityIMD Wireless Powering security

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Fig.3 Wireless IMD Power charge

Inductor

Pacemaker

Electromagnetic wave

Oscillator

Physical: Wireless Charge Circuit

Cyber: Two-Level, Chaos-based Resonance Frequency Tuning algorithms

Fig.4 CPS-oriented security solution

- It is meaningless to use conventional cryptographies to encrypt the power charge waves- Energy transfer is entirely different from data transfer

MotivationMotivation

““It is estimated that as much as 10% of all high-tech products It is estimated that as much as 10% of all high-tech products sold globally are counterfeit which leads to a conservative sold globally are counterfeit which leads to a conservative estimate of $100 billion of revenue loss.”estimate of $100 billion of revenue loss.”

[Guajardo et al, 2008][Guajardo et al, 2008]

Several invasive and semi-invasive physical Several invasive and semi-invasive physical

tampering methods have been developed,tampering methods have been developed,

which made it possible to learn the ROM-which made it possible to learn the ROM-

based keys through attacks and compromise based keys through attacks and compromise

systems by using counterfeit copies of thesystems by using counterfeit copies of the

secret information.secret information.

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Layered Architecture and Layered Architecture and Modularized DesignModularized Design

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1010

A Holistic ViewpointA Holistic Viewpoint

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A Possible Solution:A Possible Solution:Defense‐in‐DepthDefense‐in‐Depth

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A Data Mining Approach to CPS Security

Use Historical Data for Anomaly Detection Use Historical Data for Anomaly Detection

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CPS Smart grid Interactions

ee

aa ccbb dd ee

aacc

bb dd ee

At this IEM, information obtained from the observable physical event yields information about the cyber

command (b)

SSTSST

PHEVPHEV LoadLoad PVPV

DGIDGI

SSTSST

PHEVPHEV LoadLoad WindWind

DGIDGI

SSTSST

BatteryBattery LoadLoad PVPV

DGIDGI

aabb

cc

dd

Read state of Physical systemaaIssue command to make a settingbbMessage exchange including partial state information

cc

Power draw or contribution on the shared power bus

dd

ee

Event due to physical flow on the shared power bus

ee

IEM1 IEM2 IEM3

Information flow usecase of a CPS

• Information Flow Security aims at guaranteeing that no high level (confidential) information is revealed to users at a low level, even in the presence of any possible cyber/physical process

• Potential information flow models for CPSs:– Non-Interference: Information does not flow from high to low if the high

behavior has no effect on what low level observer can observe– Non-Inference: leaves a low level observer in doubt about high level events.– Non-deducibility: Given a set of low-level outputs, no low-level subject

should be able to deduce anything about the high-level inputs [Sutherland].– Composition of deducibly secure systems: not composable [McCullough]– McCullough`s Generalized noninterference-secure property considers non-

determinism of real systems

PUFsPUFs

Physical Unclonable Functions(PUFs)Physical Unclonable Functions(PUFs) -a function which is an innovative circuit primitive that exploits the -a function which is an innovative circuit primitive that exploits the

unique intrinsic uncontrollable physical features which are introduced unique intrinsic uncontrollable physical features which are introduced by manufacturing process variations.by manufacturing process variations.

Physical Objects

Process Variations

Unpredictable Behavior

Easy to Evaluate

Hard to Clone

PUFPUFPUFPUF

Anti-counterfeiting marks for ICs

Thank you!Thank you!

Questions? Questions?

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