Unified Architecture for Large-Scale Attested Metering

Michael LeMay

George Gross

Carl Gunter

Sanjam Garg

Outline

• Introduction

• Advanced Metering Overview

• Threat Model

• Security Architecture

• Application to Threat Model

• Future Work

Introduction

• Problem: Advanced Meters exhibit a number of security and privacy vulnerabilities

• Project Objective: Create a secure, private, and extensible architecture for future advanced meters

• Approach: Attested Metering: Apply Trusted Computing (TC) and virtualization technology to secure Advanced Metering network communications and computation

Advanced Metering Infrastructure (AMI)

• Advanced Meters: Electronic utility meters with bidirectional network connections to the Meter Data Management Agency (MDMA)

• Network types:– RF wireless (ZigBee/802.15.4, Wi-Fi/802.11, proprietary)– Power-Line Communication (PLC)– Broadband over PowerLines (BPL)– Cellular (CDMA, GSM)– Phone line

• Benefits:– Customer control– Demand response– Improved reliability

Advanced Meter Functions

• Read data such as kWh consumption

• Disconnect/reconnect power remotely

• Request demand response from premise

• Execute diagnostics

• Reset meter (change season mode)

• Set date/time

• Clear tables

• Log in (username/password)

• Log out

Metering Interactions

Partial threat model

• Unethical customer– May attempt to modify metering messages to

steal service– Has legitimate physical access to meter, could

modify it

• Overly-intrusive MDMA– Could use high-resolution metering data to

determine behavior of metered residents

• Publicity seeker– Cracker or virus author seeking physical

disruption to garner publicity

Hart, 1989; Residential energy monitoring and computerized surveillance via utility power flows

Security Architecture Layers

Security Architecture

• Use hypervisor on embedded processor to isolate metering applications

• Control network communications to external entities to prevent undesirable data leakage

• Use remote attestation to guarantee integrity of system components and individual VMs

Approach: Unethical Customer

• Review:– May attempt to modify metering messages to steal

service– Has legitimate physical access to meter, could modify

it

• Remote attestation with virtualization verified by MDMA to ensure software was not tampered

• Physical tampering important (and very common) but mostly outside our scope– Sometimes detectable if customer cuts connection to

meter, causing outage notification to be transmitted

11

Measurement

What software are you running?Certify the software and TPM.OK, I trust you to calculate the bill. MeasurementMeasurementMeasurement

0x5413bcd731a40x5413bcd731a4,0x8baaaf53,…

Approach: Intrusive MDMA

Virus/Worm Attack

Virus/Worm Attack

Future Work

• Address issues surrounding software distribution, updates, and removal

• Port to embedded architecture such as ARM or Atmel AVR, or other microcontroller used in modern meters

• Define and address key management issues

• Explore security-critical value-added applications for advanced meters, such as emergency network retasking

Questions?

• Website– http://seclab.uiuc.edu/attested-meter

• Michael LeMay– mdlemay2@cs.uiuc.edu

• George Gross– gross@uiuc.edu

• Carl A. Gunter– cgunter@cs.uiuc.edu

Appendices

AMI (cont.)

• Standards:– ANSI C12.19:

• Specifies how data is laid out in a meter, in terms of predefined tables

• Meter functions invoked by writing to special table and reading results from other tables

– ANSI C12.18:• Specifies how C12.19 tables are accessed using

an optical port (or RS-232 in rare cases)

– ANSI C12.22:• Similar to C12.18, but works with any network

C12.18 port

21

Virtualization

• Hypervisors, or Virtual Machine Monitors (VMMs), run entire guest operating systems in isolated system partitions– Provide strong isolation between guests to prevent

software by one vendor from interfering with software by another vendor

22

Trusted Computing Problem

• Software is controlled by machine operator• Machine operator, software distributor, or

attacker can maliciously subvert software– Modify binary– Run on untrusted hardware– Attach debugger to monitor operation

• Software publisher has no assurance that software is being used in unmodified state, as intended

Remote Attestation

• Uses keys and Platform Configuration Registers (PCRs) embedded in Trusted Platform Module (TPM) to attest to integrity of system configuration

• Possible assurances:– System running trusted software– System equipped with valid TPM

• Applications can also attest to the states of specific data files

Approach: Curious Eavesdropper

• Review:– Someone casually spying on neighbor– Probably wouldn’t go beyond scripted attack

tools

• Use network technologies that support per-link encryption, not network-wide shared keys– If necessary, use cryptographic tunnels

Approach: Motivated Eavesdropper

• Review:– Thief, criminal seeking intelligence on victims– May be willing to physically modify hardware

• “Soft” attacks addressed by strong encryption.

• Physical attacks important but outside our scope

Approach: Active Attacker

• Review:– Wants to destabilize grid or cause blackout– Could perform DoS to block demand

reduction signals– Could directly attack remote disconnect

function on many meters to disconnect homes and businesses

• Properly authenticate and authorize MDMA, customer, and any other entities with access to control functions on meters.

Prototype Hardware

• Hardware:– Dell laptop with TPM and USB ZigBee

interface emulating meter– RS-232 connected ammeter– USB-connected UPS emulating battery

backup, outage detection, and frequency measurement

– X10 home automation devices– Desktop PC with RS-232 ZigBee interface

emulating customer PC or MDMA

Prototype HW Overview

Prototype Hardware

Prototype Software

• Java implementation of ANSI C12.19 with C12.22

• Xen Virtual Machine Monitor• Linux Integrity Management

Architecture (IBM)• TrouSerS: IBM Linux TCG Software Stack• jTSS: Java wrapper for TrouSerS

Prototype Applications

• Consumer portal– Provides realtime data about energy usage,

demand response actions, and audit logs to customer

– Allows customer to:• Verify operation of external network filter• Monitor transmissions from VMs• Check audit logs for administrative actions

performed on meter

Prototype Applications (cont.)

• Meter Data Management VM– Provides billing data, outage & restoration

notifications, and maintenance information to MDMA

– Accepts price schedules from MDMA

• Demand Response VM– Processes direct Demand Response (DR)

requests from MDMA VM– Enacts customer DR preferences based on

price signals received from MDMA VM

How can you help us?

• Please give us feedback!

• Visit our website for more information: http://seclab.uiuc.edu/attested-meter

• We welcome donations of metering hardware and software– Helps us to understand capabilities of

practical devices– Directs our research to help solve actual

problems in real devices