Taking Total Control of Voting Systems: Firmware Manipulations on an Optical Scan Voting Terminal

Nicolas Nicolaou

Voting Technology Research (VoTeR) CenterDepartment of Computer Science and Engineering

University of Connecticuthttp://voter.engr.uconn.edu

24th Annual ACM Symposium on Applied ComputingSAC 2009, Honolulu, Hawaii

Joint work with:Seda Davtyan, Sotiris Kentros, Aggelos Kiayias, Laurent Michel, Alexander Russell, Narasimha Shashidhar, Andrew See andAlexander A. Shvartsman

Motivation Electronic Voting Technologies

Direct Recording Electronic (DRE) Touch Screen w/ or w/out printer, not directly voter-

verifiable Optical Scan (OS) tabulator

VVPAT – Voter Verifiable Paper Audit Trail Used in over 50% of counties in 2008

Case Study, Premier AccuVote-OS (AVOS): Wide use in US elections, but…

Can be tampered with if memory card is removed [Hursti’05]

Can be tampered with if memory card is sealed in [EVT’07] Reports by other workers and CA, CT, FL, AL,…

Safe-use procedures can be followed, but all under the assumption that firmware is trusted

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Question

Can the Can the FirmwareFirmware of Voting of Voting Machines be Machines be TrustedTrusted??

In particular: Can the In particular: Can the FirmwareFirmware of AccuVote tabulator be of AccuVote tabulator be

TrustedTrusted??

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Work performed by the UConn VoTeR Center on request of the Connecticut Secretary of the State as a part of the overalleffort to evaluate voting equipment, and to enable and performeffective technological audits, pre- and post-election.

Our Findings Firmware of AVOS can be analyzed

Without access to vendor specifications or source code Using off-the-shelf third party tools (<$300) Under the contractual right to “display or disseminate

all information and data related to election results” Three firmware manipulations targeting:

Enabling Effective Auditing: Faithful and fast memory dumping

Audit Improvement (also potential Privacy Violation): “Leak” Ballot Contents

Revealing Weaknesses: Alteration of Election Result Swapping candidate counters

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Understanding the System Election Management System (GEMS):

Ballot Design and Central Tabulation Serial port communication with AVOS

Transferred data stored on the AVOS memory card

AVOS Terminal: Hardware Components Software Components

Firmware Memory Card Contents

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Hardware External

LCD Dot Matrix Printer Ballot Reader Input Buttons 128K 40 Pin Epson

Memory Card

Internal 8Mhz MicroController

Emulates an Intel 80186

128K SRAM 128K Firmware EPROM

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Software Firmware

Version 1.96.6 Stored in a UV light erasable 128K EPROM Responsible for all the functions of the terminal Unencrypted / Unauthenticated: the terminal will

boot modified firmware without a single warning

Memory Card contents Programmed through GEMS Election-specific programming

Election Data and Control Flags depending on the Elections

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Understanding Memory Card Format

Crucial for Auditing purposes Memory Card can be divided in 5 major

sections: Header Log Election Data Bytecode (AccuBasic) Counters

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Gaining Access: Serial Port Control over the transmission

One way communication from terminal via a serial line

Identified AVOS communication Methodology Place byte to be sent in a buffer Unmask the serial transmission interrupt to place

the byte from the byte on the wire.

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Manipulation 1: AVOS as a Card Reader Goal: Transmit MC data from AVOS to PC

Improve Auditing Obtain clean and faithful image of the card contents Enable auditing of large number of cards

Motivation AVOS built-in dumping procedure

Unfaithful transmission of the contents Potential modification of the audit log Too slow for mass auditing ( ~2min per card)

Card Reader/Writer are very hard to find and are slow This type of memory cards discontinued ca. 1998 Even if available, the commercial reader can take 1/2 hour

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Manipulation 1: AVOS as a Card Reader Delivery of Memory Card Data:

Inject a function to read the memory card contents Utilizing Memory Card access control

Transmit one byte at a time to the serial line Utilizing Serial Port access control

Speeding Up Card Dumping: Implemented standard Run Lengths Encoding algorithm

Large part of card data contains sequences of identical values Reduced card dumping from 2min to 20sec

Enabled the dump and inspection of large number of cards

Avoid alteration of card contents, e.g., audit log

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Manipulation 2: Leaking Ballot Data Dual Significance of the Result:

Benign alteration of firmware: Enhance Hand Count Audit

Potential malicious alteration: Violation of Voter Privacy

Implementation AVOS side:

Transmit the candidate counters after each ballot cast PC side:

Wait for incoming counters Upon receipt of counters compute the difference of current

counter image and the locally stored counter image Counter difference reveal the ballot votes

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Manipulation 2: Leaking Ballot Data Used in Hand Count Audit

Ballot as read by AVOS presented on the screen Poll worker may verify validity of the ballot

Reduces audit time Reduces audit errors Reveals ballot read errors

Demonstrates Possible Violation of Voter Privacy Using the same technique during the election Extract order of the ballots cast

Next: Hybrid OS terminal that displays votes as cast Voter could verify their votes as recorded by the

machine

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Manipulation 3: Swapping Candidate Counters Time Bomb Attack during Election

Behave “nicely” during pre-election testing “Hit” during the actual elections

Implementing vote swapping: Swap votes for predefined candidates If votes < threshold do not swap

Also avoids pre-election testing detection Otherwise swap after the elections are closed

Swap is done at the closing of elections and before the election report is printed.

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Demonstration T=10: Pre-Election Testing

Manipulation 3: Swapping Candidate Counters

Original Firmware Modified Firmware

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Demonstration T=10: At Poll Closing

Manipulation 3: Swapping Candidate Counters

Original Firmware Modified Firmware

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Conclusions and Discussion Demonstrated 3 AVOS firmware manipulations

Used for: Fast and Faithful Memory Card dumping Potential for: Leaking Ballot Data Potential for: Swapping Candidate Counters

Our results underscore the need for Pre and Post election audits Incorporation of firmware cryptographic integrity

check at the hardware level

Answer to our question: Firmware of an e-voting terminal Firmware of an e-voting terminal

is is notnot necessarily trustworthy necessarily trustworthy 04/22/2317 VoTeR Center – SAC’09

Thank you!

Questions?

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