GAO 

United States Government Accountability Office

Report to Congressional Requesters

BORDER SECURITY

Better Usage of 

Electronic Passport 

Security Features 

Could Improve Fraud 

Detection 

January 2010 

GAO-10-96 
What GAO Found

United States Government Accountability Office

Why GAO Did This Study

Highlights

Accountability Integrity Reliability

January 2010

BORDER SECURITY

Better Usage of Electronic Passport Security 

Features Could Improve Fraud Detection 

Highlights of GAO-10-96, a report to 

congressional requesters 

In 2005, the Department of State 

(State) began issuing electronic 

passports (e-passports) with 

embedded computer chips that 

store information identical to that 

printed in the passport. By 

agreement with State, the U.S. 

Government Printing Office (GPO) 

produces blank e-passport books. 

Two foreign companies are used by 

GPO to produce e-passport covers, 

including the computer chips 

embedded in them. At U.S. ports of 

entry, the Department of Homeland 

Security (DHS) inspects passports. 

GAO was asked to examine 

potential risks to national security 

posed by using foreign suppliers 

for U.S. e-passport computer chips. 

This report specifically examines 

the following two risks: (1) Can the 

computer chips used in U.S. 

e-passports be altered or forged to 

fraudulently enter the United 

States? (2) What risk could 

malicious code on the U.S. 

e-passport computer chip pose to 

national security? To conduct this 

work, GAO reviewed documents 

and interviewed officials at State, 

GPO, and DHS relating to the U.S. 

e-passport design and 

manufacturing and e-passport 

inspection systems and procedures. 

What GAO Recommends

GAO recommends that DHS 

implement the systems needed to 

fully verify e-passport digital 

signatures at U.S. ports of entry, 

and in coordination with State, 

implement an approach to obtain 

the necessary data to validate the 

digital signatures on U.S. and other 

nations’ e-passports. DHS agreed 

with our recommendations. 

State has developed a comprehensive set of controls to govern the operation 

and management of a system to generate and write a security feature called a 

digital signature on the chip of each e-passport it issues. When verified, digital 

signatures can help provide reasonable assurance that data placed on the chip 

by State have not been altered or forged. However, DHS does not have the 

capability to fully verify the digital signatures because it has not deployed 

e-passport readers to all of its ports of entry and it has not implemented the 

system functionality necessary to perform the verification. Because the value 

of security features depends not only on their solid design, but also on an 

inspection process that uses them, the additional security against forgery and 

counterfeiting that could be provided by the inclusion of computer chips on 

e-passports issued by the United States and foreign countries, including those 

participating in the visa waiver program, is not fully realized. 

Protections designed into the U.S. e-passport computer chip limit the risks of 

malicious code being resident on the chip, a necessary precondition for a 

malicious code attack to occur from the chip against computer systems that 

read them. GPO and State have taken additional actions to decrease the 

likelihood that malicious code could be introduced onto the chip. While these 

steps do not provide complete assurance that the chips are free from 

malicious code, the limited communications between the e-passport chip and 

agency computers significantly lowers the risk that malicious code—if 

resident on an e-passport chip—could pose to agency computers. Finally, 

given that no protection can be considered foolproof, DHS still needs to 

address deficiencies noted in our previous work on its computer systems to 

mitigate the impact of any malicious code that may be read from e-passport 

computer chips and infect those systems. 

Contents of the U.S. E-passport Computer Chip 

Source: GAO analysis based on State Department information. 

• Hash values

• Digital signature

• Document signer 

 certificate

• Name

• Date of birth

• Place of birth

• Gender

• Nationality

• Document number

• Expiration date

Biographical data

Biometric data

• Facial image

Security data

View GAO-10-96 or key components.

For more information, contact Dr. Nabajyoti 

Barkakati at (202) 512-4499 or 

barkakatin@gao.gov. 
Page i GAO-10-96 

Contents 

Letter 1

Background 3 

E-passports Have Reasonable Safeguards to Assure That Computer 

Chip Data Cannot Be Altered or Forged, but Ports of Entry Lack 

the Capabilities to Use Them 13 

Malicious Code Does Not Pose a Significant Risk to U.S. E-passport 

Computer Chips or Federal Computer Systems That Read Them 21 

Conclusions 33 

Recommendations for Executive Action 34 

Agency Comments and Our Evaluation 34 

Appendix I Scope and Methodology 36 

Appendix II Digital Signatures and Public Key Cryptography 38 

Appendix III Comments from the Department of Homeland 

Security 43 

Appendix IV Contact and Staff Acknowledgments 45 

Figures 

Figure 1: Gemalto E-passport Chip and Book Production Process 9 

Figure 2: Infineon E-passport Chip and Book Production Process 10 

Figure 3: Contents of the U.S. E-passport Computer Chip 15 

Figure 4: Using Public Key Cryptography to Provide Data 

Confidentiality 39 

Figure 5: Using Public Key Cryptography to Provide Data Integrity 

and Authentication 39 

Figure 6: Creating a Digital Signature 40 

Figure 7: Verifying a Digital Signature 41 

 Border Security 
Abbreviations 

ANSI American National Standards Institute 

CBP U.S. Customs and Border Protection 

DHS Department of Homeland Security 

GPO Government Printing Office 

IC integrated circuit 

ICAO International Civil Aviation Organization 

IT information technology 

NIAP National Information Assurance Partnership 

NIST National Institute of Standards and Technology 

NSA National Security Agency 

PKI public key infrastructure 

RF radio frequency 

RFID radio frequency identification 

US-VISIT United States Visitor and Immigrant Status Indicator 

Technology 

This is a work of the U.S. government and is not subject to copyright protection in the 

United States. The published product may be reproduced and distributed in its entirety 

without further permission from GAO. However, because this work may contain 

copyrighted images or other material, permission from the copyright holder may be 

necessary if you wish to reproduce this material separately. 

Page ii GAO-10-96 Border Security
Page 1 GAO-10-96 

United States Government Accountability Office

Washington, DC 20548 

 

January 22, 2010 

The Honorable Henry Waxman 

Chairman 

The Honorable John Dingell 

Chairman Emeritus 

Committee on Energy and Commerce 

House of Representatives 

The Honorable Bart Stupak 

Chairman 

Subcommittee on Oversight and Investigations 

Committee on Energy and Commerce 

House of Representatives 

In 2005, the Department of State (State) began producing and issuing 

electronic passports (e-passports). These new e-passports have an 

embedded computer chip that stores information identical to that printed 

in the passport, including the traveler’s name, date of birth, photo, 

passport number, and passport expiration date. By comparing the 

information contained on the chip with the information printed in the 

passport, inspecting officials can more readily identify whether the photo 

or the biographical information has been altered or counterfeited, which 

provides greater assurance of the integrity of the passport. 

State’s Bureau of Consular Affairs is responsible for the design and 

issuance of passports, and U.S. Customs and Border Protection (CBP) in 

the Department of Homeland Security (DHS) inspects the documents at 

ports of entry to the United States. By agreement with State, the U.S. 

Government Printing Office (GPO) produces blank e-passport booklets. 

Among the many components that are used to make e-passport booklets, 

GPO has contracts with two European companies to produce the 

e-passport covers, including the manufacturing and inlaying of the 

computer chips into the e-passport covers. Both European companies use 

subcontractors in Asia for parts of the work. Concerns have been raised 

that the use of foreign-produced computer chips introduces risks to the 

integrity of the U.S. e-passport. 

 Border Security 
 

In response to your request, this report focuses on potential risks to 

national security posed by the use of foreign suppliers for U.S. electronic 

passports. Specifically, it examines the following two risks: (1) Can the 

computer chips used in U.S. e-passports be altered or forged to 

fraudulently enter the United States? (2) What risk could malicious code 

on the U.S. e-passport computer chip pose to national security? 

To determine whether e-passport chips can be altered or forged so that a 

traveler could fraudulently enter the United States, we interviewed 

officials from State’s Bureau of Consular Affairs and reviewed State 

Department policies, procedures, and guidance documents regarding the 

public key infrastructure (PKI) used to protect the data on the e-passport 

computer chip and assessed them against relevant International Civil 

Aviation Organization (ICAO) and National Institute of Standards and 

Technology (NIST) standards and guidelines. We interviewed officials at 

one passport agency and reviewed systems documentation to understand 

how U.S. e-passports are personalized. We determined the extent to which 

information stored on U.S. e-passport computer chips is inspected at U.S. 

ports of entry by interviewing DHS and CBP officials and reviewing 

documentation regarding the systems and procedures used to inspect 

e-passports at the ports of entry. 

To determine whether malicious code on the e-passport chips poses a risk 

to national security, we determined how U.S. e-passport computer chips 

are manufactured and incorporated into the production of blank U.S. 

e-passport booklets based on interviews with GPO and manufacturer 

officials and reviews of GPO documentation. We met with officials from 

NIST and the National Counterterrorism Center to determine the level of 

threat that exists to U.S. e-passports. We interviewed GPO and State 

officials and reviewed documentation that describes the U.S. e-passport 

computer chip architecture and operations. We reviewed documents 

governing the manufacturing of the blank e-passport covers. We identified 

protections that have been designed into the e-passport computer chip as 

well as controls that are in place to reduce the possibility of malicious 

code on the e-passport computer chip. 

Additional details on our scope and methodology can be found in 

appendix I. We conducted this performance audit from June 2008 to 

January 2010 in accordance with generally accepted government auditing 

standards. Those standards require that we plan and perform the audit to 

obtain sufficient, appropriate evidence to provide a reasonable basis for 

our findings and conclusions based on our audit objectives. We believe 

Page 2 GAO-10-96 Border Security
 

that the evidence obtained provides a reasonable basis for our findings 

and conclusions based on our audit objectives. 

U.S. passports are official documents that are used to demonstrate the 

bearer’s identity and citizenship for international travel and reentry into 

the United States. Under U.S. law, the Secretary of State has the authority 

to issue passports, which may be valid for up to 10 years.1

 Only U.S. 

nationals may obtain a U.S. passport, and evidence of citizenship or 

nationality is required with every passport application. Federal regulations 

list disqualifying situations under which U.S. citizens are not eligible for a 

passport, such as those who are subjects of a federal felony arrest warrant. 

Background 

The security of passports and the ability to prevent and detect their 

fraudulent use are dependent upon a combination of well-designed 

security features, solid issuance procedures for the acceptance and 

adjudication of the application and the production of the document, and 

inspection procedures that utilize the available security features of the 

document. A well-designed document has limited utility if it is not well 

produced or if inspectors do not utilize the security features to verify the 

authenticity of the document. 

In 2005, State began issuing e-passports, which introduced an enhanced 

design and physical security features. GPO manufactures blank e-passport 

booklets for State using a variety of materials from different suppliers. 

Currently, GPO has two suppliers—Infineon and Gemalto—under contract 

for the covers of the e-passports.2

 These covers include the computer chip 

embedded in the back cover that can communicate using contactless ID 

technology. Security-minded versions of this technology are employed in 

contactless smart cards used in applications such as automatic banking 

and identification. As of February 1, 2009, the State Department had issued 

over 30 million e-passports. 

 

1

A tourist passport, for individuals 16 years or older, is valid for 10 years from the date of 

issuance; it is valid for 5 years for younger travelers. An official passport, for federal 

employees traveling on official government business, and a diplomatic passport, for 

government officials with diplomatic status, are each valid for 5 years from the date of 

issuance. 

2

One contract was originally awarded to Axalto, which later merged with GemPlus to 

create Gemalto. 

Page 3 GAO-10-96 Border Security
 

To combat document fraud, security features are used in a wide variety of 

documents, including currency, identification documents, and bank 

checks. Security features are used to prevent or deter fraudulent alteration 

or counterfeiting of such documents. In some cases, an altered or 

counterfeit document can be detected because it does not have the look 

and feel of a genuine document. For instance, in U.S. passports, detailed 

designs and figures are used with specific fonts and colors. While these 

features are not specifically designed to prevent the use of altered or 

counterfeit documents, inspectors can often use them to identify 

nongenuine documents.3

Document Security 

Features 

Security features of travel documents are assessed by their capacity to 

secure a travel document against the following threats: 

• counterfeiting—unauthorized construction or reproduction of a travel 

document, 

• forgery—fraudulent alteration of a travel document, and 

• impostors—use of a legitimate travel document by people falsely 

representing themselves as legitimate document holders 

While security features can be assessed by their individual ability to help 

prevent the fraudulent use of the document, it is more useful to consider 

the entire document design and how all of the security features help to 

accomplish this task. Layered security features tend to provide improved 

security by minimizing the risk that the compromise of any individual 

feature of the document will allow for unfettered fraudulent use of the 

document. While most security features in the U.S. e-passport are physical 

features, the introduction of the computer chip also allows for the use of 

electronic security features. 

Inspection of Travel 

Documents to Enter the 

United States 

In general, at ports of entry, travelers seeking admission to the United 

States must present themselves and a valid travel document, such as a 

passport, for inspection to a CBP officer. The immigration-related portion 

of the inspections process requires the officer to confirm the identity and 

 

3

We previously reported on security features of State-issued travel documents, including 

e-passports, in GAO, Border Security: Security of New Passports and Visas Enhanced, 

but More Needs to Be Done to Prevent Their Fraudulent Use, GAO-07-1006 (Washington, 

D.C.: July 31, 2007). 

Page 4 GAO-10-96 Border Security
 

determine the admissibility of the traveler by questioning the individual 

and inspecting the presented travel documents. In the first part of the 

inspection process—primary inspection—CBP officers inspect travelers 

and their travel documents to determine whether they should be admitted 

or referred for further questioning and document examination. If 

additional review is necessary, the traveler is referred to secondary 

inspection—in an area away from the primary inspection area—where 

another officer makes a final determination to admit the traveler or deny 

admission for reasons such as the presentation of a fraudulent or 

counterfeit passport. 

E-passport Computer Chip 

Construction and 

Communication 

The chips used in the U.S. e-passports are integrated circuits (IC) that are 

essentially complete computers that contain a central processing unit, 

various types of memory, and other components that perform specialized 

functions such as random number generation and advanced cryptographic 

processing. The chips contain both hardware and software. The hardware 

circuitry and the operating system are implanted into the various layers of 

the chip in a process called photolithography, which employs a technique 

called masking wherein the chip’s circuitry is defined on a series of glass 

plates called the photomask. The photomask is used as a template to 

transfer the pattern of the chip’s electronic components into the various 

layers of the physical chip. Once implanted, the circuitry is considered 

permanent and not changeable except through physical attack. 

While the chip’s operating system is implanted into the chip through the 

photomask at chip creation time, other software needed on the chip—for 

example, the traveler data—are written to the chip later, during 

personalization of the chip. 

The e-passports are designed as contactless proximity cards, and 

communication with the embedded chip is only via a radio frequency (RF) 

link established according to standard methods with a device generally 

called a reader. To support global acceptance and interoperability of 

e-passports, ICAO issued standards that define how data are to be stored 

on and read from e-passports, including the RF communications.4

According to the ICAO standards, contactless communication with the 

 

4

ICAO, Machine Readable Travel Documents, Part 1 Machine Readable Passports, Volume 

2 Specifications for Electronically Enabled Passports with Biometric Identification 

Capability, ICAO 9303 Part 1, Sixth Edition (2006). 

Page 5 GAO-10-96 Border Security
 

e-passport is governed by ISO/IEC 14443, an international standard that 

defines the transmission protocol used to transfer data between the reader 

and the chip.5

 Higher-level reading from and writing to the chip is 

implemented through the ISO/IEC 7816-4 command set.6

 ISO 7816-4 is an 

international standard set of commands used to communicate with the 

chip and to control all reading from and writing to the chip based on a 

strict command/ response scheme. The reader initiates all commands to 

the chip and the chip provides the expected response. The chip itself 

cannot initiate any communications with the reader. ISO 7816-4 includes 

controls to limit read and write access to the chip to authorized parties. 

The United States issues e-passports with both ISO/IEC type A and type B 

interface connections. Both types use the same transmission protocol, but 

vary in how communications are established between the chip and the 

reader and in how information is encoded for transmission. 

The chip has no onboard power, but instead pulls the energy it needs from 

the electromagnetic field emitted by the reader. The e-passport antenna 

receives the electromagnetic energy from the reader and converts it to 

electric current to power the chip. The chip can be powered and 

communicate only when it is in close proximity—up to about 10 

centimeters—to an appropriate reader.7

 With both types of chips, the 

antenna is a component external to the chip and separately attached to it 

as part of the overall book cover manufacturing process. 

While the communication protocols and command set are standardized, 

the operating system and other software used on the chips are vendorspecific. As is typical with smart card ICs, the software on the e-passport 

chips is partitioned into three general areas: the IC dedicated software, the 

basic embedded software, and the application embedded software. The IC 

dedicated software contains software used for testing purposes and 

software to provide other services to facilitate usage of the hardware on 

The Software Contents of the 

Chip 

 

5

The ISO/IEC 14443 standard is composed of four parts, covering physical characteristics, 

radio frequency power and signal interface, initialization and anticollision procedures, and 

transmission protocols. 

6

ISO/IEC, Identification cards—Integrated circuit cards, Part 4: Organization, security 

and commands for interchange, ISO/IEC 7816-4, Second Edition (Jan. 15, 2005). 

7

With special equipment and under certain circumstances, the read distance can be 

increased somewhat. 

Page 6 GAO-10-96 Border Security
 

the IC. The IC dedicated software is developed by the IC manufacturer and 

it is part of the photomasks of the chips. 

The basic embedded software is typically not provided by the chip 

manufacturer, but is usually developed by a third party and delivered to 

the chip manufacturer for incorporation into the chip’s photomask. An 

important component of the basic embedded software is the operating 

system for the chip. The operating system implements the ISO 7816-4 

command set and controls all communication between the chip and the 

outside world. 

The third major partition of software on the chip is the application 

embedded software, which is also typically provided by a third party and 

provides functionality specific to the particular application for which the 

chip is intended to be used. In the case of the U.S. e-passports, the 

application software is data contained in a file layout using an open, ICAOspecified logical data structure used for machine-readable travel 

documents. 

The E-passport Production 

Process 

In producing e-passport booklets for State, GPO has tapped into the 

existing global smart card industry, resulting in a wide number of different 

companies involved in the e-passport chip production and inlay process. 

Two separate companies were awarded contracts to supply chips for the 

U.S. e-passports. Infineon, a German company, fabricates its own chips 

and embeds a commercial operating system from a third-party company 

on them. Gemalto, a Dutch company, obtains chips from NXP, a Dutch 

semiconductor manufacturer. Gemalto provides NXP with its own 

operating system, which NXP embeds within the chip prior to shipping the 

chip to Gemalto. 

Although each of these contractors takes a different path to create and 

provide e-passport covers to GPO, both use a common subcontractor for 

attachment of the antenna to the chip and the inlaying of the chip into the 

back cover of the e-passport booklet. GPO itself finishes production of the 

e-passport booklet by inserting the paper pages into the covers, installing a 

metal strip down the inside spine for RF shielding, and, in a process 

termed pre-personalization, preparing the chip for use by the State 

Department. State personalizes the e-passport by printing bearer data onto 

the data page and writing digital data onto the chip as part of its issuance 

procedures. 

Page 7 GAO-10-96 Border Security
 

As seen in figure 1, several steps are involved in the production of an 

e-passport using Gemalto’s e-passport booklet. Gemalto involves several 

subcontractors to produce the cover before it is delivered to GPO. For 

instance, while the operating system software is created by Gemalto, it is 

implanted on the chip when it is fabricated by NXP. Companies overseas 

are also involved in the production of the chip and its incorporation into 

the e-passport cover. 

Gemalto E-passport Chip and 

Booklet Production Process 

In pre-personalization, GPO tests and formats the chips, preparing them 

for personalization by State, and finishes overall construction of the 

e-passport booklet. GPO then ships the finished, blank e-passport books to 

the 21 State Department passport issuing offices around the country that 

then personalize and issue them to U.S. citizens, as needed.8

 

8

State has 19 domestic passport agencies and centers that accept, examine, adjudicate, and 

process passport applications; they issue passports to those determined to be citizens or 

nationals of the United States. State also has two domestic passport personalization 

facilities that produce and issue the passports once one of the passport centers or agencies 

has approved the passport application. 

Page 8 GAO-10-96 Border Security
 

Figure 1: Gemalto E-passport Chip and Book Production Process 

Photomask data generation

Hardware and software photomask is created

Vendor

Photomask production

Mask is etched onto glass plates

Vendor

Wafer fabrication

Wafer is fabricated

Vendor

Distributing

Transit stop

Vendor

Assembly, module test, and treatment

Package assembly and final test

Vendor

Wafer test and treatment

Wafer grinding, test, and sawing

Vendor

Wafer bump

Antenna attachment point is added

Vendor

Antenna attachment and inlay into book 

Antenna and chip set in back cover 

Vendor

Test and pre-personalization formatting

Test and format chip, assemble blank book

GPO

Personalization and issuing

Personalize and issue e-passports

State Department

Source: GAO analysis based on GPO and Gemalto information.

Secure storage

Vendor

Page 9 GAO-10-96 Border Security
 

Similar to Gemalto’s production process, the production process at 

Infineon also involves several subcontractors to produce the booklet cover 

before it is delivered to GPO (see fig. 2). The operating system and other 

embedded software used on the Infineon chips are developed by a thirdparty company, and shipped to Infineon for incorporation into the 

photomask pattern. As with the Gemalto production process, GPO tests 

and pre-personalizes each chip, finishes the books, and distributes the 

finished, blank e-passport books to the 21 passport-issuing offices. 

Infineon E-passport Chip and 

Book Production Process 

Figure 2: Infineon E-passport Chip and Book Production Process 

Source: GAO analysis based on GPO and Infineon information.

Photomask data generation

Hardware and software photomask is created

Vendor

Photomask production

Mask is etched onto glass plates

Vendor

Wafer fabrication

Wafer is fabricated

Vendor

Preassembly, assembly, and test

Wafer thinning, die bonding, and wire bonding

Vendor

Personalization and issuing

Personalize and issue e-passports

State Department

Test and pre-personalization formatting

Test and format chip, assemble blank book

GPO

Contactless test and inspection

Final test

Vendor

Antenna attachment and inlay into book

Antenna and chip set in back cover

Vendor

Page 10 GAO-10-96 Border Security
 

Since 1997, GAO has identified federal information security as a high-risk 

area.9

 Malicious code is one of the primary threats to federal information 

security. NIST defines malicious code—sometimes called malware—as “a 

program that is inserted into a system, usually covertly, with the intent of 

compromising the confidentiality, integrity, or availability of the victim’s 

data, applications, or operating system or of otherwise annoying or 

disrupting the victim.”10 Malicious code can be used for many purposes 

and come in many forms. For example, malicious code might be designed 

to delete files on a system or repeatedly attempt access to a system service 

and thus effectively shut it down. The effects of malicious code can range 

from performance degradation to compromise of mission-critical 

applications. Some common forms of malicious code include viruses, 

worms, and Trojan horses. Viruses infect a system by attaching themselves 

to host programs or data files. Worms are self-contained programs that can 

self-replicate and do not require human interaction to spread through a 

system or network. Trojan horses are nonreplicating programs that appear 

benign but are designed with a malicious purpose. 

Threats to E-passport 

Computer Chips 

Malicious code often takes advantage of vulnerabilities in a system’s 

software to either spread or execute. For example, a common 

vulnerability, known as a buffer overflow, redirects system control to a 

malicious program through badly designed software. Inadequate controls 

on a network’s connections or services are another common vulnerability 

that allows malicious code to spread. Common protections against 

malicious code include input checking at the boundaries of a system, such 

as at external interfaces to a system; network controls to lower the 

possibility that malicious code could spread within a system; and patch 

management to address vulnerabilities in the system’s software that 

malicious code can exploit. 

In general, a successful malicious code attack first requires that the 

malicious code get into a system. This can occur, for example, by inserting 

infected media into the computer or through incomplete controls on the 

system’s network connections. Second, the malicious code needs to 

spread to those areas of a system to which it wants to cause damage. 

Malicious code can spread in many ways, including various network 

protocols and services and also in simple file transfers. Finally, malicious 

 

9

GAO, High-Risk Series: An Update, GAO-09-271 (Washington, D.C.: January 2009). 

10NIST, Guide to Malware Incident Prevention and Handling, SP800-83 (Gaithersburg, 

Md.: November 2005). 

Page 11 GAO-10-96 Border Security
 

code needs to be executed, often by taking advantage of vulnerabilities in 

a system’s software. 

Therefore, in the case of e-passports, a successful malicious code attack 

from the chip would first require that malicious code get on the chip. 

Second, that it get transferred from the chip onto agency computers 

during the e-passport inspection process and then spread to vulnerable 

areas within those systems. And, finally, the malicious code would have to 

be executed. 

Although communication with the chips is designed to be via the 

contactless ID interface that complies with the ISO 7816-4 standard, which 

includes an authentication procedure to limit read and write access to the 

chip to authorized parties, an alternate, illicit way data can be attempted to 

be read from or written to the chip is through physical tampering 

techniques. In general, the aim of such an attack is to discover confidential 

data stored on the chip—such as cryptographic keys—which can be used 

to open access to the chip via the contactless interface. 

Common Criteria Common Criteria is an international standard method for evaluating 

security features of information technology (IT) components. The U.S. 

portion of this effort is coordinated through a partnership of NIST and the 

National Security Agency (NSA) called the National Information 

Assurance Partnership (NIAP). It provides a framework for evaluating 

security features of IT components. The Common Criteria program 

evaluates commercial-off-the-shelf information assurance and information 

assurance-enabled products. These products can be items of hardware, 

software, or firmware. Evaluations are performed by accredited Common 

Criteria testing laboratories whose results are then certified by a validation 

body. A product is considered Common Criteria certified only after it is 

both evaluated by an accredited laboratory and validated by the validation 

body. 

Common Criteria certifications are expressed in a seven-step assurance 

scale called Evaluation Assurance Levels. The seven ordered levels 

provide an increasing measure of confidence in a product’s security 

functions. All evaluated products that receive a Common Criteria 

certificate appear on a validated products list, which is available on the 

Common Criteria Web site. 

To facilitate the efficient use of testing resources, an international 

agreement was developed under which one country’s Common Criteria 

Page 12 GAO-10-96 Border Security
 

certifications would be recognized by the other participating countries.11

This is intended to eliminate unnecessary duplication of testing efforts. 

Common Criteria certifications need to be carefully considered. We have 

reported previously that the fact that a product appears on the validated 

products list does not by itself mean that it is secure.12 A product’s listing 

on any Common Criteria validated products list means that the product 

was evaluated against its security claims and that it has met those claims. 

The extent to which vendor-certified claims provide sufficient security for 

a given application is another question. 

A complex environment has been established to provide reasonable 

assurance that the data contained on electronic passports can be used to 

help determine whether an individual should be admitted to the United 

States. The overall control environment depends on each party effectively 

implementing the controls that have been established to govern its 

operation and utilize the controls implemented by the other agencies. 

State uses a technology commonly referred to as public key cryptography 

to generate digital signatures on the data it writes to the computer chips 

on the e-passport. These digital signatures, when effectively implemented, 

can help provide reasonable assurance that integrity has been maintained 

over the data placed on the chip by State. Our review found that DHS has 

not implemented the capabilities needed to completely validate the digital 

signatures generated by State before relying on the data, which adversely 

affects its ability to obtain reasonable assurance that the electronic data 

provided in a chip were the same data that State wrote in the e-passport. 

While DHS has some controls that somewhat mitigate this weakness, it 

does little to ensure that altered or forged electronic data can be detected. 

Accordingly, until DHS implements this functionality, it will continue to 

lack reasonable assurance that data found on e-passport computer chips 

have not been fraudulently altered or counterfeited. 

E-passports Have 

Reasonable 

Safeguards to Assure 

That Computer Chip 

Data Cannot Be 

Altered or Forged, but 

Ports of Entry Lack 

the Capabilities to 

Use Them 

 

11Thirteen countries are recognized as certificate producers under the Arrangement on the 

Mutual Recognition of Common Criteria Certificates in the Field of IT Security: the United 

States, Australia, Canada, France, Germany, Japan, the Netherlands, New Zealand, Norway, 

Spain, South Korea, Sweden, and the United Kingdom. 

12GAO, Information Assurance: National Partnership Offers Benefits, but Faces 

Considerable Challenges, GAO-06-392 (Washington, D.C.: Mar. 24, 2006). 

Page 13 GAO-10-96 Border Security
 

ICAO has issued e-passport standards that have been adopted by the 

United States and other countries.13 As part of its specifications for 

e-passports, ICAO requires the use of digital signatures and a public key 

infrastructure to establish that the data contents of the computer chip are 

authentic and have not been changed since being written. A PKI—a system 

of hardware, software, policies, and people—is based on a sophisticated 

cryptographic technique known as public key cryptography. The use of a 

PKI for e-passports primarily serves to provide (1) data integrity (the 

electronic data placed on the passport have not been changed), and (2) 

authentication (the country issuing the e-passport was the source of the 

data). In its standards, ICAO specifies only the use of well-known 

cryptographic algorithms for use in e-passports. 

State Generates Digital 

Signatures That Can Be 

Used to Provide Needed 

Assurance 

As discussed in appendix II, public key cryptography is used to generate 

and validate digital signatures. In particular, the “public key” is used to 

validate the digital signature that is used to authenticate the data being 

signed. However, a means is necessary for the user to reliably associate a 

particular public key with a document signer. The binding of a public key 

to a document signer is achieved using a digital certificate, which is an 

electronic credential that guarantees the association between a public key 

and a specific entity.14

In agreement with ICAO standards for e-passports, State generates and 

writes a digital signature on the chip of each e-passport during the 

personalization process. As illustrated in figure 3, State stores the 

following information on the e-passport computer chip: biographical 

information about the traveler, the traveler’s facial image, and security 

data. The biographical data and facial image are organized into data 

groups for storage on the e-passport. Each data group is condensed using 

a hashing algorithm and the resulting hash values are stored in the security 

data.15 A digital signature is generated on these hash values, which 

represent the data stored on the e-passport computer chip. Hence, the 

security data on an e-passport consist of three key elements: the data 

 

13ICAO 9303, Part 1, Volume 2. 

14A digital certificate is created by placing the entity’s name, the entity’s public key, and 

certain other identifying information in a small electronic document that is stored in a 

directory or other database. Directories may be publicly available repositories kept on 

servers that act like telephone books for users to look up others’ public keys. 

15A hash is created using a special one-way cryptographic algorithm that is designed to 

process an input file to produce a unique condensed fixed-length message digest. 

Page 14 GAO-10-96 Border Security
 

group hash values, the digital signature, and the certificate needed to 

validate the digital signature. This certificate—known as the document 

signer certificate—is associated with a digital signature on a U.S. 

e-passport’s data and is used to validate that the signed data contained in 

that passport were actually generated by State. The keys and certificates 

associated with U.S. e-passports are established in a hierarchical manner 

to establish a “chain of trust” that a third party, such as DHS, can use to 

obtain reasonable assurance that the data contained in the passport are 

the data that were actually written on to the e-passport by State. 

Figure 3: Contents of the U.S. E-passport Computer Chip 

Source: GAO analysis based on State Department information. 

• Hash values

• Digital signature

• Document signer 

 certificate

• Name

• Date of birth

• Place of birth

• Gender

• Nationality

• Document number

• Expiration date

Biographical data

Biometric data

• Facial image

Security data

State has developed a comprehensive set of controls to govern the 

operation and management of the PKI that generates the digital signatures 

used to help assure the integrity of the passport data written to the chip. 

These controls include the development of policies and practices that are 

consistent with best practices described in federal guidelines. For 

example, State’s policies and procedures for generating and storing digital 

signatures and certificates from cryptographic modules minimize the risk 

of compromise or unauthorized disclosure. Further, State’s procedures 

require the use of cryptographic modules validated against the level 3 

Page 15 GAO-10-96 Border Security
 

criteria of FIPS 140-2, which is consistent with federal best practices and 

requirements.16

If properly validated, the digital signatures on State’s e-passports should 

provide those reading the chip data, including DHS, reasonable assurance 

that the data stored on the chip were written by State and have not been 

altered. Proper validation includes verifying that the document signer 

certificate was issued by the State Department. 

DHS Has Not Implemented 

the Capability to Fully 

Verify E-passport Digital 

Signatures 

In July 2007, we reported that DHS was not fully using a key security 

feature of the U.S. e-passport—namely the data stored on the chip.17 At 

that time, DHS had not fully deployed e-passport readers to all primary 

inspection lanes at all ports of entry and did not have a schedule to do so. 

We also reported that the implemented e-passport reader solution was not 

capable of validating e-passport digital signatures, which would help to 

ensure that the data written to the e-passport chips have not been altered. 

Since that time, while DHS has begun planning an acquisition for new 

e-passport readers, DHS has made no further deployments of e-passport 

readers, nor has it implemented a solution that would allow for the full 

verification of the digital signatures on e-passport computer chips. 

In 2006, as a part of the United States Visitor and Immigrant Status 

Indicator Technology (US-VISIT) system, DHS deployed 237 e-passport 

readers at 33 air ports of entry—212 are installed in primary inspection 

lanes and 25 are installed in training areas.18 No e-passport readers are 

deployed in secondary inspection areas. While these 33 air ports of entry 

were chosen because they process the largest volume of travelers—about 

97 percent—from Visa Waiver Program countries, the majority of lanes at 

these airports do not have e-passport readers.19 Even though the same 

DHS Has Not Fully Deployed 

E-passport Readers to the Ports 

of Entry 

 

16NIST, Security Requirements for Cryptographic Modules, FIPS 140-2 (Gaithersburg, Md.: 

May 25, 2001). 

17GAO-07-1006. 

18US-VISIT is a program designed to use biometric and biographic information to control 

and monitor the pre-entry, entry, status, and exit of foreign visitors. US-VISIT’s goals are to 

(1) enhance the security of U.S. citizens and visitors, (2) facilitate legitimate travel and 

trade, (3) ensure the integrity of the U.S. immigration system, and (4) protect the privacy of 

visitors. 

19Citizens of Visa Waiver Program countries are not required to obtain a U.S. visa to enter 

the United States for business or tourism purposes for 90 days or less. 

Page 16 GAO-10-96 Border Security
 

e-passport readers may be used to read U.S. e-passports, U.S. citizens are 

primarily processed through lanes at these air ports of entry that are not 

equipped with e-passport readers. 

At equipped primary inspection lanes, CBP officers can use e-passport 

readers to access the biographical information and digitized photograph 

stored on the e-passport chip. To read e-passports, officers place the 

biographical page of the e-passport on the reader’s glass plate. The reader 

then electronically scans the biographical information printed on the page 

and uses it to access the information stored in the e-passport’s chip. Once 

the biographical data and photograph from the chip are displayed on the 

primary inspection computer screen, the officer is to compare the 

information displayed with the information on the biographical page of the 

passport and verify that they match. The results of any validation activities 

conducted on the data by the system are also presented to the officer. Any 

mismatches could indicate fraud. 

While a total of 500 e-passport readers were purchased by the US-VISIT 

program. DHS has made no further deployments of e-passport readers 

since 2006. Those not deployed are in storage, used for training, or used to 

support system development activities. Following the deployment at the 33 

air ports of entry in 2006, responsibility for deploying the e-passport 

readers was shifted from the US-VISIT program to CBP. CBP officials 

partially attributed the lack of progress in deploying e-passport readers to 

its failure to allocate funding for the activity since it assumed the 

responsibility from US-VISIT. According to DHS officials, the slower than 

expected times to read data from e-passport chips also influenced its 

decisions to not further the deployment of the e-passport readers. 

In 2008, DHS transferred $11.4 million of no-year funds from US-VISIT to 

CBP for planning, purchasing, and deploying e-passport readers at all CBP 

primary processing lanes and secondary inspection areas at the ports of 

entry. According to CBP officials, it is currently planning an acquisition for 

new e-passport readers. As a part of the acquisition planning, CBP also 

expects to determine whether it will replace the 500 currently deployed or 

stored e-passport readers with new readers that will likely have better 

performance than the current readers. According to DHS, CBP is planning 

an e-passport reader procurement that will allow for the full deployment 

of e-passport readers in fiscal year 2011. 

Page 17 GAO-10-96 Border Security
 

In our prior work, we recommended that DHS develop a deployment 

schedule for providing sufficient e-passport readers to U.S. ports of entry.20

With the identification of funding for the effort, CBP has initiated planning 

for further deployment of e-passport readers, but has not yet developed a 

deployment schedule. Until DHS installs e-passport readers in all 

inspection lanes, CBP officers will not be able to take advantage of the 

data stored on e-passport chips. For instance, without e-passport readers, 

CBP officers are unable to read the photograph and biographic 

information stored on the e-passport chip, information that would better 

enable officers to detect many forms of passport fraud, including 

impostors and the alteration or substitution of the photos and information 

printed in the passports, and help to determine the traveler’s identity and 

admissibility into the United States. 

While DHS’s systems conduct some validation activities to ensure the 

integrity of the data on the e-passport chip, it does not have adequate 

assurance that the data stored on the chip have not been changed since 

they were authored by a legitimate issuing authority—in the case of U.S. 

e-passports, the State Department. 

DHS Has Not Implemented the 

Public Key Infrastructure 

Needed to Verify E-passport 

Digital Signatures 

In primary inspection lanes that are equipped with e-passport readers, 

CBP’s workstations conduct a series of checks using data read from the 

e-passport computer chip, including the biographical data, the facial 

image, and the security data. First, the CBP workstation verifies that the 

biographical data read from the computer chip match that read from the 

printed biographical page. Second, the CBP workstation calculates the 

hash values of the data groups read from the computer chip and compares 

them with the hash values stored in the security data. If available, the CBP 

workstation will also use the digital certificate to verify the digital 

signature. The expiration date of the e-passport and the digital certificate 

are also checked. Finally, if the e-passport has been previously read by 

CBP, the hash value of the facial image is compared with the value stored 

by CBP. If this is the first time the e-passport has been encountered, the 

hash value is stored for future comparisons. Any mismatches are to result 

in an error being displayed to the CBP officer. 

Further, in October 2008, DHS began to make U.S. passport data available 

to CBP officers in primary inspection. DHS is now receiving U.S.-issued 

passport data through a datashare initiative with the Department of State. 

 

20GAO-07-1006. 

Page 18 GAO-10-96 Border Security
 

CBP has modified its workstations to retrieve this additional information 

when U.S. passports, including e-passports, are processed. When CBP 

officers enter U.S. passport data into appropriately configured CBP 

workstations, the photograph of the traveler, as issued by the State 

Department, will be displayed to the officer.21 As e-passports are issued by 

State, the corresponding information is made available to DHS through the 

datashare. State worked with DHS to transfer data on all valid historical 

U.S. passports. As more historical U.S. passport information becomes 

available, more photographs will be displayed to primary officers upon 

processing a U.S. citizen through primary inspection. 

However, the key step that is missing is that the CBP workstation does not 

validate the legitimacy of the public key used to verify the digital 

signature. Such a validation would provide assurance that the public key 

in the document signer certificate was generated by the State Department. 

Without this verification, CBP does not have reasonable assurance that the 

e-passport data being protected by the digital signature were written by 

the State Department because forgers or counterfeiters could simply 

generate the keys necessary to digitally sign the forged data and include 

their own certificate in the e-passport for verification purposes. Checking 

the legitimacy of the certificate containing the public key that is used in 

the digital signature validation process would effectively mitigate this risk. 

When generated, the document signer certificates are themselves digitally 

signed. However, CBP does not have access to the public keys necessary 

to validate these digital signatures. While DHS tested the functionality of 

storing and using this information to verify the certificates included by 

State and other nations on e-passports using the CBP workstation, the 

functionality was not implemented for operations because the 

infrastructure to collect and maintain the international certificate database 

did not exist. According to DHS officials, this function was a US-VISIT 

requirement, but did not get implemented, in part, because a DHS 

component that would be responsible for operating the public key 

database was never identified. DHS officials also stated that the slow 

performance of reading e-passports diminished the importance of 

implementing this function. 

 

21According to CBP, it has updated its workstation software to display the additional 

information when conducting primary inspections at airports and at pedestrian and vehicle 

lanes at land ports of entry. 

Page 19 GAO-10-96 Border Security
 

Not being able to check the legitimacy of the document signer certificates 

affects not only CBP’s ability to verify the integrity and authenticity of the 

data written to U.S. e-passport computer chips, but also its ability to verify 

the integrity and authenticity of computer chip data on any country’s 

e-passport. The United States requires all 35 participants in the Visa 

Waiver Program to issue e-passports, and ICAO has estimated that over 50 

countries issue e-passports. Because CBP does not have the necessary 

information to fully validate the digital signatures that these countries 

generate, it does not have reasonable assurance that data signed by those 

countries were actually generated by the authorized passport issuance 

agency for that country. Hence, it cannot ensure that the integrity of the 

data stored on the e-passport’s computer chip has been maintained. 

Two key issues need to be resolved for CBP to be able to rely on data 

stored on e-passport computer chips. First, a database needs to be 

established and populated with the digital certificates needed to fully 

validate the digital signatures that can be accessed by CBP inspection 

workstations at the ports of entry. An approach needs to be developed and 

implemented to populate the database with the needed information, 

including State Department data for U.S. e-passports, that can be used to 

fully validate the digital signatures. According to ICAO, this information 

should be distributed only through secure diplomatic channels.22 Second, 

CBP needs to develop and implement functionality on its inspection 

workstations to access the database when e-passport data are read to 

verify that the legitimate passport-issuing authority signed the data being 

relied upon. Until these two key issues are addressed, CBP will continue 

to lack reasonable assurance that data found on e-passport computer 

chips have the necessary integrity; hence, the security enhancements that 

could be provided by e-passport computer chip data against counterfeiting 

and forgery are not completely realized. 

 

22One source of certificate data could be the ICAO Public Key Directory. ICAO’s directory is 

to include only document signer certificates that have been validated by ICAO. However, 

there is not universal use of the ICAO Public Key Directory by e-passport-issuing countries. 

Page 20 GAO-10-96 Border Security
 

Protections designed into the U.S. e-passport computer chip limit the risks 

of malicious code being resident on the chip, a necessary precondition for 

a malicious code attack to occur from the chip against computer systems 

that read them. GPO and State have taken additional actions to decrease 

the likelihood that malicious code could be introduced onto the chip. 

While these steps do not provide complete assurance that the chips are 

free from malicious code, the limited communications between the 

e-passport chip and agency computers significantly lowers the risk that 

malicious code—if resident on an e-passport chip—could pose to agency 

computers. As we previously discussed, the e-passport’s digital signature 

can provide reasonable identification of unauthorized modification of the 

user data areas—including modifications resulting from the introduction 

of malicious code. Finally, given that no protection can be considered 

foolproof, DHS still needs to address deficiencies noted in our previous 

work on the US-VISIT computer systems to mitigate the impact of 

malicious code, should it infect those systems. 

Malicious Code Does 

Not Pose a Significant 

Risk to U.S. 

E-passport Computer 

Chips or Federal 

Computer Systems 

That Read Them 

U.S. E-passport Chip 

Designs and 

Manufacturing Processes 

Limit Exposure to 

Malicious Code 

Security features designed into the e-passport computer chips, including 

the digital signature, provide protections against the introduction of 

malicious code onto the chip during the e-passport booklet production 

process. For example, among other features, the chips include physical 

tamper protections that aid in sensing or thwarting physical attacks, a 

cryptographic authentication procedure to lock the contactless interface 

against unauthorized access, and incorporation of a digital signature that 

can be used to identify any unauthorized modification of the user data 

areas. 

As of 2007, NIST had not been able to identify any known cases of a 

malicious code attack against a computer network from a contactless 

chip.23 Nevertheless, both NIST and DHS agree that it is possible and have 

generally identified physical tamper attacks as threats to embedded 

electronic chips in contactless applications such as e-passports. 

Physical Tamper Protections 

Help Ensure against Physical 

Attacks on the Chip 

Physical tamper attacks involve stripping away the chip’s outer coverings, 

exposing the electronic circuitry on the wafer, and analyzing or monitoring 

chip activity by inserting electronic probes onto components etched into 

the wafer. In general, the aim of such an attack is to discover confidential 

 

23NIST, Guidelines for Securing Radio Frequency Identification (RFID) Systems, SP800-

98 (Gaithersburg, Md.: April 2007), 4-7. 

Page 21 GAO-10-96 Border Security
 

data stored on the chip—such as cryptographic keys—which can be used 

to open access to the chip via the contactless interface. In terms of a 

malicious code threat, the purpose then would be to write malicious code 

onto the chip via the RF interface. 

In its guide to chip-level security for contactless ICs, DHS identifies 

common methods used in physical tamper attacks on contactless ICs.24 For 

example, after removing top layers of plastic or other coverings and 

uncovering the electrical surfaces of the chip, attackers could probe into 

the various chip layers in an attempt to understand its processing. 

Common methods of physical attack are those related to (1) fault 

introduction, (2) IC monitoring, and (3) reverse engineering. The purpose 

of each of these attacks is ultimately to uncover secret information—such 

as cryptographic keys or passwords—that would allow an attacker to 

open the chip for read/write access via the contactless interface. In fault 

introduction, attackers attempt to introduce faults randomly, at specific 

times during the processing, or in specific locations on the IC circuitry, to 

gain additional information about the chip processing during such faults, 

which could provide clues to the memory location of secret keys. 

Similarly, such clues can be uncovered using IC monitoring, where readers 

or probes placed on the chip’s internal circuitry are used to monitor 

calculations or flows of data on the chip. Finally, attackers could attempt 

to reverse engineer the computer chip to decipher its hardware 

architecture and read the secret information. 

In its guide, DHS identifies countermeasures for each of these types of 

attack. For example, protections against fault introduction include 

implementing sensors that detect when parameters, such as light or 

temperature, vary outside of expected values. If such variations are 

sensed, the chip may automatically reset or even disable itself. Protections 

against IC monitoring might include encrypting the traffic flowing along 

the internal circuitry so that interpretation would be difficult. Protections 

against physical analysis include encrypting information stored in memory 

and scrambling the design of the logic contained in the operating system 

when laid down in memory during IC creation. Well-designed security 

microcontrollers, with numerous security features and support for mutual 

authentication and sophisticated cryptographic functions, can be designed 

 

24DHS Science and Technology Directorate, Chip-Level Security for RFID Smart Cards 

and Tags. 

Page 22 GAO-10-96 Border Security
 

to make it extremely difficult, costly, and time-consuming for attackers to 

compromise. 

In its solicitation for the e-passport covers, which included the computer 

chips, GPO specified several hardware and software requirements to 

protect against physical attack, including specific features to assist in 

protection against power and timing attacks. It also included requirements 

for sensors to monitor, for example, temperature and voltage variations, 

which might be indicative of a physical tamper attack. The chips used in 

the U.S. e-passports are considered security microcontrollers designed for 

applications where security is an important consideration, such as 

payment, identity, and secure access and, as such, they incorporate several 

features against physical tamper attacks. Both types of chips used in the 

e-passports have incorporated some recommended countermeasures for 

all of the common categories of attack identified by DHS. For example, the 

chips incorporate temperature and light sensors to monitor when those 

operating conditions vary from expected values and employ memory 

encryption against reverse engineering of the chip . 

While it is not possible to provide complete protection against the more 

invasive physical attacks, the goal is to make the cost of mounting such an 

attack prohibitive. While the threat of physical attack to the embedded 

chips in the e-passport cannot be completely discounted, the security 

features incorporated into the microcontrollers in U.S. e-passports make a 

physical tamper attack impractical. 

During production of the e-passport covers, the manufacturers, their 

subcontractors, and at GPO and State—or anywhere en route between 

these sites—the chips are protected from unauthorized access through the 

contactless interface by authentication procedures based on cryptography. 

Cryptographic-Based 

Authentication Procedures 

Control Contactless Access to 

the Chip during Booklet 

Production 

The manufacturing and personalization process for the e-passport booklet 

is complex and involves many handoffs between different sites, 

companies, and sometimes different countries. For example, while both 

e-passport cover contractors originate chip manufacturing in Europe, they 

also send the chips to various third-party companies in Asia for additional 

manufacturing steps. The overall process can take almost 2 years from the 

time the chip leaves the fabrication plant until it is finally issued by the 

State Department to a bearer as part of an e-passport. 

During the production life cycle of the e-passport book—from chip 

creation at the chip manufacturers through to personalization by State—

contactless access to the chip is controlled by a symmetric cryptography 

Page 23 GAO-10-96 Border Security
 

authentication procedure. Cryptographic algorithms provide different 

measures of strength, depending on the algorithm and the overall length of 

the keys involved. According to NIST estimates, the version used on the 

e-passports can, at best, provide protection from a brute force attack until 

2030.25

This locking mechanism not only controls access to the chip, but 

differentially allows only certain functions to be performed. 

Several other design features limit the chance that malicious code could 

be placed on the chip. For example, according to GPO, an additional step 

used to protect the e-passport chips from unauthorized access during the 

manufacturing process takes advantage of standard industry practice to 

not include customer identification with chips during production runs. 

During the chip-manufacturing process, an anonymous cataloging scheme 

is employed that makes it difficult to associate bulk lots of chips with their 

destined applications. Therefore, on the production floor, it cannot be 

determined which chips are to be used in U.S. e-passports. 

Other Design and 

Manufacturing Steps Help 

Mitigate the Risk from 

Malicious Code 

In addition, after the chips are manufactured and incorporated into the 

e-passport cover, steps are taken by GPO and State to protect the user 

data areas of the chip from tampering. First, as part of its formatting 

procedures to prepare the chips for personalization, GPO ensures that the 

user data area is free from any data—including malicious code. During the 

formatting of the user data area, if any memory cell is found to be 

defective, then GPO discards the e-passport booklet. Therefore, any 

malicious code successfully implanted within the user data area after 

manufacture and through any of the chip’s travels through its production 

cycle up until it arrived at GPO would be erased from the chip. 

As we previously discussed, during the e-passport personalization process, 

a digital signature is applied to the data to help assure the integrity and 

authenticity of the data written to the chip. One of the benefits of the 

digital signature is that any insertion of malicious code into, for example, 

the bearer’s digital image would be caught, provided the digital signature 

is fully and properly verified. Such a successful check would provide 

reasonable assurance that malicious code has not been inserted into the 

user data areas of the chip memory since it was personalized by State. 

 

25See NIST, Recommendation for Key Management—Part 1: General, SP 800-57 

(Gaithersburg, Md.: March 2007). 

Page 24 GAO-10-96 Border Security
 

Limited Communications 

between the E-passport 

Chip and Agency 

Computers and Security 

Certifications and Reviews 

Mitigate Risks Posed by 

Malicious Code 

GPO and State have taken steps to gain confidence that their e-passport 

computer chips are secure. While these steps do not provide complete 

assurance that the chips are free from malicious code, the limited 

communications between the e-passport chip and agency computers 

significantly lowers the risk that malicious code that could be resident on 

an e-passport chip could pose to agency computers. The chips have been 

tested for both interoperability and conformance to ICAO specifications 

and exercised by GPO as part of their formatting process. The chips have 

undergone a formal, independent process to validate some aspects of their 

security. GPO and State also periodically conduct security reviews of the 

chip manufacturer sites. 

One key feature that mitigates the risk that malicious code on the chip 

could pose to agency computers is the highly restricted nature of the data 

exchange between the chip and agency computers during the reading of 

the e-passport. The e-passport computer chip adheres to ISO 14443 and 

ISO 7816-4 for communications through the contactless interface. The 

standards restrict the computer chip to a slave role whereby it responds 

only to a specific set of commands with known and limited response data. 

Because the chip cannot independently initiate communication with a 

reader, the flow of data from the chip to the reader and host computer can 

be precisely controlled and limited to only what is expected by the host 

computer. 

Controls on the Interface 

between the E-passport 

Computer Chip and Agency 

Computers Limit the 

Opportunities for Transfer of 

Malicious Code 

The result is that opportunities for the covert embedding of malicious 

code within data transferred from the chip to agency computers are 

correspondingly limited. For example, the passport number, bearer’s 

name, and date of birth are data sets restricted to a well-defined set of 

characters and are of fixed length. Consequently, if a reader accepts inputs 

only within these bounds, it will limit the risk posed by malicious code. 

The digital image of the bearer is the only data set transferred that is of 

enough size to provide for opportunities to hide malicious code. The image 

is formatted according to a standard graphics format that facilitates 

integrity checking of its contents. According to DHS officials, when 

e-passports are read, the data from the chip are verified both by the 

e-passport reader as well as by the agency host computer before the data 

are processed. 

Testing Helps to Verify Proper Functioning of E-passport Chip 

Communications 

Prior to contract award, and at various points thereafter, the U.S. 

e-passport chips have undergone testing for a variety of purposes. 

Page 25 GAO-10-96 Border Security
 

According to GPO officials, the solicitation for the e-passport covers was 

based on State Department requirements for specific functionality, 

security, performance, and availability. For example, it included 

requirements for the chip to meet ISO 14443 communications and ISO 

7816-4 command set standards and other standard specifications. As part 

of the award selection process, GPO, State, NIST, and NSA conducted 

testing of sample books from each bidder to determine whether they 

would meet requirements as specified in the request for proposal. 

During pre-award testing, for example, GPO ran initial tests to ensure 

basic functionality as specified by ISO 7816-4, including the ability to 

initialize, read, write, and lock the chip. GPO also ensured that each 

e-passport cover was of the correct form and thickness so that it could 

mechanically pass through its production equipment suite. The sample 

booklets then went to State, which conducted tests to ensure the books 

could work with its personalization systems. 

According to NIST officials, they performed electronic testing that looked 

at the potential for eavesdropping, jamming, and remote activation 

(skimming). For eavesdropping, the test was conducted to determine 

whether the legitimate communication could be intercepted, but no 

attempt was made to see if the encrypted communication could be 

understood. For jamming, the purpose was to determine whether 

legitimate communications with the chip could be prevented. For remote 

activation, the purpose was to determine the distance from which a reader 

could elicit a response from the chip, but no attempt was made to test the 

basic access control or to read the data on the chip. NIST also conducted 

different types of durability tests including static bend, dynamic bend, 

climate, chemical resistance, physical protection of the integrated circuit 

chip, and electromagnetic testing. None of NIST’s tests were designed to 

test for the presence of malicious code on the chip. While the tests 

exercised some portions of ISO 14443 and ISO 7816-4, NIST did not 

conduct any tests to ensure full conformance with these standards. 

NSA officials stated that they conducted electronic testing of the booklet, 

but this was confined to radio frequency testing and shielding testing 

specifically tasked by GPO to evaluate the susceptibility of the booklet to 

skimming by looking at the distance over which the booklet’s chip could 

become energized. NSA performed no substantive tests of communication 

with the chip and no testing at all with regard to malicious code. 

As part of GPO’s normal pre-personalization processing, GPO exercises 

and tests each chip’s functionality to verify, among other things, the 

Page 26 GAO-10-96 Border Security
 

correct reading and writing of every chip. GPO’s processing does not 

systematically exercise every chip function or the full ISO 7816-4 

command set and associated error handling. GPO officials said that while 

they test the basic functionality of the chip as they proceed through the 

pre-personalization processing, full ISO 14443 communications and ISO 

7816-4 command set processing—including ensuring that all error 

handling is performed correctly—is done as part of the international ICAO 

interoperability and conformance tests held approximately every 2 years. 

The State Department is the official U.S. representative to these tests, 

although GPO frequently participates, by request, in support of State. 

According to ICAO, the interoperability and conformance tests are 

intended to accomplish two things. First, they ensure that e-passports 

from different countries can be read by readers provided by multiple 

vendors. Second, they ensure compliance with various aspects of the ISO 

14443 communication and ISO 7816-4 command set standards. The U.S 

e-passport chips have been part of some of the interoperability and 

conformance tests that have been run in the last several years.26

All these tests provide important assurances for their stated purposes by 

exercising functionality, in particular the limited e-passport chip 

communications, that helps to protect against the risk of malicious code. 

In general though, such testing is limited to verifying functionality and 

cannot provide absolute assurance that malicious code has not been 

implanted onto the e-passport computer chip. 

The creation of the computer chip used in U.S. e-passports is a complex 

process that involves many components created by different entities. 

Because the U.S. government does not control the entire supply chain for 

all the components on the chip, it relies on security features provided by 

the chip component suppliers, the extent to which these suppliers test and 

Security Certifications and 

Security Reviews Provide Some 

Assurance That Computer 

Chips Are Free from Malicious 

Code 

 

26According to GPO officials, because of competitive pressures within the smart card 

industry, the chip manufacturers will often modify their chips to enhance their processing. 

These changes may involve chip circuitry changes, for example, to increase the speed of 

the chip’s processing. Sometimes the chip operating system needs to be modified as well to 

mesh with the circuitry changes. GPO officials stated that State generally likes to take 

advantage of these enhanced chips and use them if it can. Therefore, sometimes the chip 

manufacturer will deliver samples of enhanced chips that GPO will evaluate separately 

from the production line. If agreed to by the Configuration Change Board—on which both 

State and GPO sit—the enhanced version of the chip may be folded into production. In 

those cases where a chip change is significant, it may trigger the need to participate in the 

full ICAO interoperability and conformance testing. Revalidation with NIST and others 

could also be needed. 

Page 27 GAO-10-96 Border Security
 

certify their products, and the extent to which these suppliers develop and 

produce the chips in a secure manner. 

Some Aspects of the Security of the Chips Were Certified Using 

Common Criteria 

NIST guidelines state that federal agencies should give substantial 

consideration in IT procurements to products that have been evaluated 

and tested by accredited laboratories against appropriate security 

specifications and requirements.27 One established mechanism for 

providing security evaluation and testing services for commercial-off-theshelf hardware, software, or firmware is Common Criteria. Common 

Criteria certifications are a well-known international standard mechanism 

for validating and documenting various security aspects of IT products. 

Evaluations are performed by accredited Common Criteria testing 

laboratories whose results are then certified by a validation body. In the 

case of the chips used in the U.S. e-passports, selected security features of 

their hardware components were evaluated using Common Criteria by a 

recognized European laboratory and certified by Germany’s Common 

Criteria certification body. 

In its solicitation for the e-passport covers, including the computer chips, 

GPO specified that preference will be given to computer chips that are 

certified at Common Criteria EAL 4+ against a Common Criteria-compliant 

Protection Profile.28 According to Common Criteria definitions, an EAL 4 

rating is intended to provide a moderate to high level of independently 

assured security. To achieve this rating, the testing lab must conduct a 

variety of structured activities, including an analysis of the security 

functions of the product using a complete interface specification and both 

the high-level and low-level design of the specific features of the product 

being tested, review and confirmation of any vendor testing that was 

conducted, and conduct of an independent vulnerability analysis 

demonstrating resistance to penetration attackers with a low attack 

potential. 

 

27NIST, Guidelines to Federal Organizations on Security Assurance and Acquisition/Use 

of Tested/Evaluated Products, SP800-23 (Gaithersburg, Md.: August 2000). 

28According to Common Criteria, a Protection Profile is an implementation-independent 

statement of security needs for an IT product. A “+” designation on an EAL rating indicates 

that security requirements beyond those specified in the Common Criteria standard were 

included in the target of evaluation and also satisfied. 

Page 28 GAO-10-96 Border Security
 

The computer chips selected for use in the e-passports each had received 

an EAL 5+ rating against a compliant Protection Profile. According to 

Common Criteria, an EAL 5 rating incorporates all of the EAL 4 

requirements and, in addition, requires, among other things, semiformal 

design descriptions, a more structured architecture, covert channel 

analysis, and improved mechanisms that provide confidence that the 

particular implementation of the product being evaluated has not been 

tampered with during development. Specific security features evaluated to 

achieve the EAL 5 rating include many useful in helping to prevent the 

introduction of malicious code. Examples of these include support for 

cryptographic functions, protections against physical manipulation, and 

features to ensure correct operating conditions for the chip. 

However, a key software component of the chip—the operating system—

was excluded from the evaluation. The operating system on the chip 

implements and controls, among other functions, the ISO 7816-4 command 

set that is the primary means of communication between the chip and the 

outside world—including agency computers. 

Under Common Criteria, it is not uncommon for critical components of a 

product to be excluded for particular evaluations. In particular, the 

exclusion of important software components, such as the operating 

system, from the Common Criteria evaluation of hardware features is not 

unusual because the higher-level software embedded on chips is often a 

third-party product and not designed by the chip manufacturer itself. The 

chip manufacturer is typically not responsible for undertaking a Common 

Criteria evaluation of third-party embedded software used on its chips. 

Typically, it would be up to the software provider to get its product 

certified using Common Criteria. However, this is an expensive and timeconsuming process. Hence, care needs to be taken with Common Criteria 

certifications that can be meaningfully understood only within the context 

of the specific subset of security functions included in the evaluation. 

We have previously noted that one of the challenges in using the National 

Information Assurance Partnership is the difficulty in matching agencies’ 

needs with the availability of NIAP-evaluated products.29 According to 

Infineon and Gemalto officials, back in 2006 when the request for proposal 

for the e-passport covers was issued, there was no Protection Profile 

available that covered the operating systems of such chips. Since that 

 

29GAO-06-392. 

Page 29 GAO-10-96 Border Security
 

time, however, Common Criteria operating systems suitable for use on 

smart cards have become available. According to GPO officials, Infineon 

provides such chips today, and GPO is in the process of transitioning them 

into production so that, at least for the Infineon line, the e-passports will 

include a Common Criteria-certified operating system. 

The user operating system contains arguably most of the software 

functioning on the chip. Therefore, obtaining assurance as to its secure 

functioning and freedom from malicious code is an important activity. 

However, given the highly restricted nature of the current communications 

between the chip and agency computers, we do not see the lack of 

Common Criteria certification of the chip operating system as significantly 

increasing the risk to agency computers from malicious code.30

While Common Criteria certification confers some assurance regarding the 

specific security functions included in the evaluation, care must be taken 

in extending that assurance into confidence in the overall security of the 

product for its intended use. GAO has previously reported that within its 

limitations, the Common Criteria process provides benefits. However, the 

lack of performance measures leaves questions unanswered as to its true 

effectiveness.31 The use of commercial products that have been 

independently tested and evaluated is only a part of a security solution 

that contributes to the overall information assurance of a product. 

GPO Has Conducted Reviews of the E-passport Computer Chip 

Manufacturing Sites 

Prior to contract award, and periodically thereafter, GPO—sometimes 

accompanied by the State Department—conducted on-site security 

reviews of the companies that manufacture the e-passport chips and the 

covers, and of some of their subcontractors. According to GPO officials, 

its reviews are concerned with not just security risks, but also with other 

risks—for example, the extent to which a site performs continuity of 

operations planning or the risk that a single source of supply for one of the 

components might pose a risk to the delivery of the components. In 

 

30If the communications between the chip and agency computers were extended beyond 

their current limited scope, the risk from malicious code on the chip would need to be 

reevaluated. For future use, the ICAO specification does allow for additional data sets to be 

passed across this interface, for example, fingerprint data and other biometrics. 

31GAO-06-392. 

Page 30 GAO-10-96 Border Security
 

conducting the security reviews, GPO officials stated that they make an 

attempt to visit every vendor involved in the production of the e-passport 

booklet, including, for example, the security ink suppliers, paper 

providers, thread providers, and the chip providers. The sites are spread 

across several countries, and within some countries there may be multiple 

sites. For example, for both Infineon and Gemalto, production of the chips 

involves several sites within Europe. 

These reviews employ an American National Standards Institute (ANSI) 

standard for security product manufacturing that covers a variety of risk 

areas, including information, IT, material, supply chain, physical intrusion, 

personnel, and disaster recovery.32 For example, the standard addresses 

such concerns as proper controlled access to restricted areas within a 

facility. During the security review, GPO generally gets a high-level 

briefing from the company and talks with staff at the site. According to 

GPO officials, they have reviewed almost every site twice since March 

2006. In recent security reviews of the chip manufacturing sites, both 

Infineon and NXP were found to be in compliance with their own stated 

security policies and meeting the Class 1 level of the ANSI standard. 

From the security reviews, GPO can get some sense of some of the 

protections in place at the development sites—for example, access control 

to development areas and security awareness training. GPO learned 

through its reviews, for example, that Gemalto has an access control 

policy wherein development premises are divided into secure and 

nonsecure zones, and the operating system development is in the secured 

zone. This provides some assurance that since physical access to the 

software destined for the chips is controlled, opportunities for the 

inclusion of malicious code can be limited. 

 

32ANSI/NASPO, Security Assurance Standards for the Document and Product Security 

Industry, ANSI/NASPO-SA-v3.0P-2005 (Washington, D.C.: March 2007). 

Page 31 GAO-10-96 Border Security
 

Given that there can be no guarantees against a malicious code attack 

originating from the e-passport computer chip, agency systems need to 

have a strong security posture, in accordance with federal government 

standards. We have previously reported on weaknesses in DHS’s US-VISIT 

computer systems, which could increase the ability of malicious code to 

infect and propagate through agency computers.33 Weaknesses, such as 

unpatched software vulnerabilities, can invite a malicious code attack and 

enhance the ability of the attack to spread across the network by leaving 

important linkages within the network unprotected. DHS needs to address 

these deficiencies to ensure that any malicious code resident on the 

e-passport chip and read onto DHS computers can be contained and its 

effect minimized. 

To Further Mitigate the 

Effect of a Malicious Code 

Attack, DHS Needs to 

Address Previously Noted 

Weaknesses in US-VISIT 

Computer Systems 

One of the strong recommendations from NIST is that computer systems 

run antivirus software, which scans systems’ files and memory spaces for 

known malware. NIST strongly recommends the use of antivirus software 

to identify and protect against malicious code. Detecting such code prior 

to its further spread can limit a malicious code infection and protect 

downstream systems. According to DHS officials, workstations that 

control the interface with the chip are protected by antivirus software, 

which includes access protections, buffer overflow protections, and 

scanning of files as they are accessed. 

One of the key weaknesses in US-VISIT that we found in 2007—patch 

management—is of particular concern with respect to malicious code that 

could be read from an e-passport. Malicious code often attacks systems by 

exploiting vulnerabilities in operating systems, services, and applications. 

When software vulnerabilities are discovered, the software vendor may 

develop and distribute a patch or workaround to mitigate the vulnerability. 

Patch management is, therefore, an important element in mitigating the 

risks associated with malicious code and the vulnerabilities they depend 

on. NIST’s, NSA’s, and DHS’s own policies stress the importance of 

keeping computer systems up to date with security patches. Outdated and 

unsupported software is more vulnerable to attacks and exploitation. NIST 

guidelines state that applying patches is one of the most effective ways of 

reducing the risk of malware incidents.34

 

33GAO, Information Security: Homeland Security Needs to Immediately Address 

Significant Weaknesses in Systems Supporting the US-VISIT Program, GAO-07-870

(Washington, D.C.: July 13, 2007). 

34NIST SP800-83. 

Page 32 GAO-10-96 Border Security
 

In our prior report, we noted that while DHS has taken steps to ensure that 

patches for the workstations’ operating system were kept up to date, some 

workstations at the ports of entry did not consistently maintain secure 

configurations. As a result, vulnerabilities left unpatched on those systems 

increase the chance of malicious code being executed should it get 

ingested.35 According to DHS officials, they are in the midst of upgrading 

workstations to a version of Microsoft Windows that contains features to 

help prevent the execution of malicious code—for example, special 

services to detect and prevent the execution of code from the data areas. 

DHS needs to ensure that it completes the upgrade of the workstations 

and that such services are enabled on workstations reading data from the 

e-passport computer chips. 

Ensuring the integrity of passports requires continual vigilance so that 

they can continue to be used to support the critical border security 

mission—facilitating the travel of those who are entitled to enter the 

United States while preventing the entry of those who are not. A welldesigned passport has limited utility if it is not well produced or border 

officers do not utilize the available security features to detect attempts to 

fraudulently enter the United States. While U.S. e-passport covers, 

including the embedded computer chip, are manufactured by foreign 

companies, State’s public key infrastructure, which is used to generate 

digital signatures during the personalization process for each issued 

passport, can provide reasonable assurance that the data written onto the 

chip were authored by State and have not been altered. However, DHS has 

not implemented the capabilities needed for CBP officers to fully utilize 

this security feature. Without e-passport readers at the ports of entry or a 

system that allows for the full validation of digital signatures on 

e-passports, CBP officers’ inspection of not only U.S. e-passports, but also 

of e-passports issued by foreign countries, including those participating in 

the visa waiver program, is affected. Without these capabilities, the 

additional security against forgery and counterfeiting that could be 

provided by the inclusion of computer chips on e-passports issued by the 

United States and foreign countries, including those participating in the 

visa waiver program, is not fully realized. 

Conclusions 

 

35DHS has provided evidence to us that it has addressed some of the weaknesses noted in 

patch management of its systems. However, others remain unresolved. 

Page 33 GAO-10-96 Border Security
 

While the use of e-passports and radio frequency communications 

represents another potential attack vector to federal computer systems, 

the risk posed by the transmission of malicious code on U.S. e-passports is 

not significant. The U.S. e-passport chips have security features that 

minimize the threat of tampering during the manufacturing and production 

process. GPO and State have also taken steps to assure the security of the 

embedded computer chips in U.S. e-passports. Because the 

communications between e-passport computer chips and federal 

computer systems have been designed to be limited, the opportunities for 

transfer of malicious code are correspondingly limited. Combined, these 

measures significantly reduce the risks from someone using e-passport 

computer chips as a conveyance for malicious code to federal computer 

systems. 

To ensure that border officers can more fully utilize the security features 

of electronic passports, we recommend that the Secretary of Homeland 

Security take the following two actions to provide greater assurance that 

electronic passport data were written by the issuing nation and have not 

been altered or forged: 

• Design and implement the systems functionality and databases needed to 

fully verify electronic passport digital signatures at U.S. ports of entry. 

• In coordination with the Secretary of State, develop and implement an 

approach to obtain the digital certificates necessary to validate the digital 

signatures on U.S. and other nations’ electronic passports. 

We provided draft copies of this report to the Secretaries of State and 

Homeland Security and to the Public Printer at the Government Printing 

Office for review and comment. We received formal written comments 

from the Department of Homeland Security, which are reprinted in 

appendix III. In its comments, DHS concurred with our recommendations. 

However, DHS believes that the report incorrectly portrays CBP’s ability 

to detect the fraudulent use of U.S. passports. DHS cites the ability of 

CBP’s officers to access U.S. passport application data from State and use 

it to detect impostors and altered data in U.S. passports. We agree that 

providing State passport data to CBP officers during the inspection 

process enhances their ability to detect the fraudulent use of U.S. 

e-passports. Nevertheless, while State has expended significant resources 

to produce an e-passport that includes contactless chip technology and 

public key cryptography to help prevent counterfeiting and forgery, DHS 

Recommendations for 

Executive Action 

Agency Comments 

and Our Evaluation 

Page 34 GAO-10-96 Border Security
 

has not implemented the capabilities to fully utilize these security features 

and is not fully realizing the security benefits of the inclusion of electronic 

technology on e-passports. 

We received informal comments from the State Department. State believes 

that the draft report presents a comprehensive and balanced assessment 

of the security of the e-passport design. We also received technical 

comments from State, GPO, and DHS, which we incorporated in the 

report, as appropriate. 

As we agreed with your offices, unless you publicly announce the contents 

of this report earlier, we plan no further distribution of it until 30 days 

from the report date. At that time, we will send copies of this report to the 

Secretaries of State and Homeland Security and the Public Printer. In 

addition, the report will be available at no charge on the GAO Web site at 

http://www.gao.gov. 

If you or your staff have any questions about this report, please contact me 

at (202) 512-4499 or barkakatin@gao.gov. Contact points for our Offices of 

Congressional Relations and Public Affairs may be found on the last page 

of this report. GAO staff who made major contributions to this report are 

listed in appendix IV. 

r. Nabajyoti Barkakati 

Chief Technologist 

nology and Engineering 

D

Director, Center for Tech

Page 35 GAO-10-96 Border Security
Appendix I: Scope and Methodology Appendix I: Scope and Methodology 

To determine whether e-passport chips can be altered or forged so that a 

traveler could fraudulently enter the United States, we interviewed 

officials from State’s Bureau of Consular Affairs and reviewed State 

Department policies, procedures, and guidance documents regarding the 

public key infrastructure (PKI) used to protect the data on the e-passport 

computer chip and assessed them against relevant International Civil 

Aviation Organization (ICAO) and National Institute of Standards and 

Technology (NIST) standards and guidelines. We interviewed officials at 

one passport issuance agency and reviewed systems documentation to 

understand how U.S. e-passports are personalized. We determined the 

extent to which U.S. e-passport computer chips are inspected at U.S. ports 

of entry by interviewing Department of Homeland Security (DHS) officials 

and reviewing documentation regarding the systems and procedures used 

to inspect e-passports at the ports of entry. Within DHS, we met with 

officials from the U.S Customs and Border Protection (CBP), the 

Screening Coordination Office, and the United States Visitor and 

Immigrant Status Indicator Technology (US-VISIT) program office. 

To determine whether malicious code on the e-passport chips poses a risk 

to national security, we determined how U.S. e-passport computer chips 

are manufactured and incorporated into the production of blank U.S. 

e-passport booklets based on interviews with the Government Printing 

Office (GPO) and manufacturer officials and our reviews of GPO 

documentation. We met with officials from NIST and the National 

Counterterrorism Center to determine the level of threat that exists to U.S. 

e-passports. We interviewed GPO and State officials and reviewed 

documentation that describes the U.S. e-passport computer chip 

architecture and operations. We reviewed documents governing the 

manufacturing of the blank e-passport covers, including GPO contracts 

with the manufacturers and the memorandum of understanding between 

GPO and State. We determined that for malicious code on the e-passport 

computer chip to be a risk to agency computers, it must first get on the 

chip, then get transferred off the chip and onto agency computers, and 

then subsequently get executed. Therefore, we identified and evaluated 

protections that have been designed into the e-passport computer chip to 

reduce the possibility of malicious code being introduced onto the chip, 

controls in place to limit the transfer of malicious code off of the chip and 

onto agency computers, and the security posture of the agency computer 

systems interfacing with the e-passport chip. We also reviewed the results 

of testing conducted on the e-passport computer chips by GPO, NIST, the 

National Security Agency, and ICAO, and through the Common Criteria 

program. We discussed and reviewed the results of security reviews 

conducted by GPO. We met with GPO, State, and CBP officials to 

Page 36 GAO-10-96 Border Security 
Appendix I: Scope and Methodology 

understand how each agency interacts with the e-passport computer chips 

and the potential risk that malicious code could pose to these agencies. 

We conducted this performance audit from June 2008 to January 2010 in 

accordance with generally accepted government auditing standards. Those 

standards require that we plan and perform the audit to obtain sufficient, 

appropriate evidence to provide a reasonable basis for our findings and 

conclusions based on our audit objectives. We believe that the evidence 

obtained provides a reasonable basis for our findings and conclusions 

based on our audit objectives. 

Page 37 GAO-10-96 Border Security
Appendix II: Digital Signatures and Public Appendix II: Digital Signatures and Public Key Cryptography 

Key Cryptography 

Cryptography is the transformation of ordinary data (commonly referred 

to as plaintext) into a code form (ciphertext) and back into plaintext using 

a special value known as a key and a mathematical process called an 

algorithm. Cryptography can be used on data to (1) hide their information 

content, (2) prevent their undetected modification, and/or (3) prevent their 

unauthorized use. A basic premise in cryptography is that good systems 

depend only on the secrecy of the key used to perform the operations 

rather than on any attempt to keep the algorithm secret. The algorithms 

used to perform most cryptographic operations over the Internet are well 

known; however, because the keys used by these algorithms are kept 

secret, the process is considered secure. 

The basis of PKI’s security assurances is a sophisticated cryptographic 

technique known as public key cryptography, which employs algorithms 

designed so that the key that is used to encrypt plaintext cannot be 

calculated from the key that is used to decrypt the ciphertext.1

 These two 

keys complement each other in such a way that when one key is used for 

encryption, only the other key can decrypt the ciphertext. One of these 

keys is kept private and is known as the private key, while the other key is 

widely published and is referred to as the public key. When used as shown 

in figure 4, public key cryptography can help to assure data confidentiality 

because only the private key can be used to decrypt the information 

encrypted using the public key. When used as shown in figure 5, public key 

cryptography can help provide authentication, nonrepudiation, and data 

integrity because the public key will only work to decrypt the information 

if it was encrypted using the private key. In both cases, ensuring the 

security of the private key is vital to providing the necessary security 

protections. If the private key is compromised, there can be little 

assurance that data confidentiality, authentication, and data integrity can 

be provided by the PKI. 

 

1

A more comprehensive discussion of public key infrastructure technology can be found in 

GAO, Information Security: Advances and Remaining Challenges to Adoption of Public 

Key Infrastructure Technology, GAO-01-277 (Washington, D.C.: Feb. 26, 2001), and NIST, 

Introduction to Public Key Technology and the Federal PKI Infrastructure, SP 800-32 

(Feb. 26, 2001). 

Page 38 GAO-10-96 Border Security 
Appendix II: Digital Signatures and Public 

Key Cryptography 

Figure 4: Using Public Key Cryptography to Provide Data Confidentiality 

Encryption Plaintext Ciphertext Decryption

Original

plaintext

Source: GAO analysis and Corel Galley (images).

Plaintext

document

Plaintext

document

Plaintext

document

Plaintext

document

Plaintext

document

Plaintext

document

sdkj;daf

 afj0pem

sdkj;daf

 afj0pem

sdkj;daf

 afj0pem

Private

key

Public

key

Figure 5: Using Public Key Cryptography to Provide Data Integrity and 

Authentication 

Encryption Plaintext Ciphertext Decryption

Original

plaintext

Source: GAO analysis and Corel Galley (images).

Plaintext

document

Plaintext

document

Plaintext

document

Plaintext

document

Plaintext

document

Plaintext

document

sdkj;daf

 afj0pem

sdkj;daf

 afj0pem

sdkj;daf

 afj0pem

Private

key

Public

key

Cryptographic techniques are used to generate and manage the key pairs 

(a public key and private key), which are in turn used to create electronic 

“certificates,” which link an individual or entity, such as State, to its public 

key. These certificates are then used to verify digital signatures (providing 

authentication and data integrity). 

Creating and Using Digital 

Signatures 

Public key cryptography can be used to create a digital signature for a 

message or transaction, thereby providing authentication, data integrity, 

and nonrepudiation. For example, if Bob wishes to digitally sign an 

electronic document, he can use his private key to encrypt it. His public 

key is freely available, so anyone with access to his public key can decrypt 

Page 39 GAO-10-96 Border Security
Appendix II: Digital Signatures and Public 

Key Cryptography 

the document. Although this seems backward because anyone can rea

what is encrypted, the fact that Bob’s private key is held only by Bob 

provides the basis for Bob’s digital signature. If Alice can successfully 

decrypt the document using Bob’s public key, then she knows that the 

message came from Bob because only he has access to the corresponding 

private key. Of course, this assumes that (1) Bob has sole control ov

private signing key and (2) Alice is sure that the

d 

er his 

 public key used to 

validate Bob’s messages really belongs to Bob. 

asible to find another message that will 

generate the same message digest. 

Digital signature systems use a two-step process, as shown in figure 6. 

First, a hash algorithm is used to condense the data into a message digest. 

Second, the message digest is encrypted using Bob’s private signing key to 

create a digital signature. Because the message digest will be different for 

each signature, each signature will also be unique, and using a good hash 

algorithm, it is computationally infe

First, a hash algorithm is used to condense the data into a message digest. 

Second, the message digest is encrypted using Bob’s private signing key to 

create a digital signature. Because the message digest will be different for 

each signature, each signature will also be unique, and using a good hash 

algorithm, it is computationally infe

Figure 6: Creating a Digital Signature 

Source: National Institute of Standards and Technology.

Bob

Hash algorithm applied

Final signed

document

contains the

original with the

encrypted hash

attached

Bob’s private

key

is applied

Encrypted Encrypted

Document to

be signed

Message

digest

Message

digest

Message

digest

Plaintext document.

Plaintext document.

Plaintext document.

Plaintext document.

Plaintext document.

Plaintext document.

Plaintext document.

Plaintext document.

Plaintext document.

Plaintext document.

Plaintext document.

Plaintext document.

Plaintext document.

Plaintext document.

Plaintext document.

Plaintext document.

Plaintext document.

Plaintext document.

Alice (or anyone wishing to verify the document) can compute the 

message digest of the document and decrypt the signature using Bob’s 

public key, as shown in figure 7. Assuming that the message digests matc

Alice then has three kinds of security assurance. First, that Bob actu

h, 

ally 

Page 40 GAO-10-96 Border Security
Appendix II: Digital Signatures and Public 

Key Cryptography 

signed the document (authentication). Second, the digital signature 

ensures that Bob in fact sent the message (nonrepudiation). And th

because the message digest would have changed if anything in the 

message had been modified, Alice knows that no one tampered with the 

contents of the document after Bob signed it (data integrity). Again, this

assumes that (1) Bob has sole control over his private signing key and 

(2) Alice is sure t

Again, this

ird, 

hat the public key used to validate Bob’s messages really 

belongs to Bob. 

Figure 7: Verifying a Digital Signature 

Source: National Institute of Standards and Technology.

Hash algorithm

applied to plain text

Bob’s public

key used

to decrypt

Encrypted

Signed document

Encrypted

Alice

Message

digest

Do they match?

Message

Me digest ssage

digest

Message

digest

Plaintext document.

Plaintext document.

Plaintext document.

Plaintext document.

Plaintext document.

Plaintext document.

Plaintext document.

Plaintext document.

Plaintext document.

A digital certificate is an electronic credential that guarantees the 

association between a public key and a specific entity. It is created 

placing the entity’s name, the entity’s public key, and certain other 

identifying information in a s

by 

mall electronic document that is stored in a 

directory or other database. 

to the 

s 

Convey 

Trust 

Digital Certificates and 

Certification Authoritie

Link Public Keys with 

Specific Users to 

Directories may be publicly available repositories kept on servers that act

like telephone books for users to look up others’ public keys. The digital

certificate itself is created by a trusted third party called a certification 

authority, which digitally signs the certificate, thus providing assurance 

that the public key contained in the certificate does indeed belong 

individual or organization named in the certificate. A certification 

Page 41 GAO-10-96 Border Security
Appendix II: Digital Signatures and Public 

Key Cryptography 

authority is responsible for managing digital certificates. The purpos

the certification authority is to oversee the generation, distribut

renewal, revocation, and suspension of digital certificates. The 

certification authority may set restrictions on a certificate, such as the 

starting date for which the certificate is valid as well as its expira

It is at times necessary to revoke digital certificates before their 

established expiration dates, for example, when the private key is 

compromised. Therefore, the certification authority is also responsible

providing certificate status information and may publish a certificat

revocation list in a directory or maintain an online status-checking 

mechanism. The PKI software in the user’s computer can verify that the 

certificate is valid by first verifying that the certificate has no

e of 

ion, 

tion date. 

 for 

e 

t expired and 

then by assuring that it has not been revoked or suspended. 

Page 42 GAO-10-96 Border Security
Appendix III: Comments from the Department Appendix III: Comments from the of Homeland Security 

Department of Homeland Security 

Page 43 GAO-10-96 Border Security 
Appendix III: Comments from the Department 

of Homeland Security 

Page 44 GAO-10-96 Border Security
Appendix IV: C

A

ontact and Staff 

cknowledgments 

Page 45 GAO-10-96 

Appendix IV: Contact and Staff 

Acknowledgments 

Dr. Nabajyoti Barkakati, (202) 512-4499 or barkakatin@gao.gov

In addition to the contact named above, William Carrigg, Richard Hung, 

and John C. Martin made key contributions to this report. 

 Border Security 

GAO Contact 

Staff 

Acknowledgments 

(460601) 
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