Technology-savvy organizations
`looking to develop a competitive
`advantage should carefully watch
`developments in biometrics.
`
`Simon Liu and Mark Silverman
`
`A Practical Guide to
`Biometric Security
`Technology
`A s organizations search for more secure
`
`authentication methods for user access,
`e-commerce, and other security appli-
`cations,biometrics is gaining increasing
`attention. But should your company use biomet-
`rics? And,if so,which ones should you use and how
`do you choose them? There is no one best bio-
`metric technology. Different applications require
`different biometrics.
`To select the right biometric for your situation,
`you will need to navigate through some complex
`vendor products and keep an eye on future devel-
`opments in technology and standards.Your options
`have never been more diverse. After years of
`research and development,vendors now have sev-
`eral products to offer. Some are relatively imma-
`ture, having only recently become commercially
`available,but even these can substantially improve
`your company’s information security posture.We
`briefly describe some emerging biometric tech-
`nologies to help guide your decision making.
`
`WHAT IS A BIOMETRIC?
`The security field uses three different types of
`authentication:
`
`Inside
`
`Glossary
`Resources
`
`• something you know—a pass-
`word, PIN, or piece of personal
`information
`(such as your
`mother’s maiden name);
`• something you have—a card key,
`smart card, or token (like a
`SecurID card); and/or
`• something you are—a biometric.
`
`Of these, a biometric is the most secure and con-
`venient authentication tool. It can’t be borrowed,
`stolen, or forgotten, and forging one is practically
`impossible. (Replacement part surgery, by the
`way, is outside the scope of this article.)
`Biometrics measure individuals’ unique physi-
`cal or behavioral characteristics to recognize or
`authenticate their identity. Common physical bio-
`metrics include fingerprints; hand or palm geom-
`etry; and retina, iris, or facial characteristics.
`Behavioral characters include signature, voice
`(which also has a physical component), keystroke
`pattern, and gait. Of this class of biometrics, tech-
`nologies for signature and voice are the most
`developed.
`Figure 1 describes the process involved in using
`a biometric system for security.
`
`Fingerprints
`A fingerprint looks at the patterns found on a
`fingertip.There are a variety of approaches to fin-
`gerprint verification. Some emulate the tradi-
`tional police method of matching minutiae; others
`use straight pattern-matching devices; and still
`others are a bit more unique, including things like
`moiré fringe patterns and ultrasonics. Some ver-
`ification approaches can detect when a live finger
`is presented; some cannot.
`A greater variety of fingerprint devices is
`available than for any other biometric. As the
`prices of these devices and processing costs fall,
`using fingerprints for user verification is gain-
`ing acceptance—despite the common-criminal
`stigma.
`
`1520-9202/01/$10.00 © 2001 IEEE
`
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`

`S E C U R I T Y
`
`Figure 1. How a biometric system works.
`
`1
`
`4
`
`Biometric
`devices
`
`Biometric
`devices
`
`2
`
`5
`
`Biometric
`enrollment
`
`Biometric
`verification
`
`7
`
`Business
`applications
`
`3
`
`8
`
`6
`
`Template
`storage
`
`Template
`storage
`
`the unique patterns of the retina. Retinal scan-
`ning can be quite accurate but does require the
`user to look into a receptacle and focus on a
`given point.This is not particularly convenient if
`you wear glasses or are concerned about having
`close contact with the reading device. For these
`reasons, retinal scanning is not warmly accepted
`by all users, even though the technology itself can
`work well.
`
`(1) Capture the chosen biometric; (2) process the biometric
`and extract and enroll the biometric template; (3) store the
`template in a local repository, a central repository, or a portable
`token such as a smart card; (4) live-scan the chosen biometric;
`(5) process the biometric and extract the biometric template;
`(6) match the scanned biometric template against stored tem-
`plates; (7) provide a matching score to business applications; (8)
`record a secure audit trail with respect to system use.
`
`Fingerprint verification may be a good choice for in-
`house systems, where you can give users adequate expla-
`nation and training, and where the system operates in a
`controlled environment. It is not surprising that the work-
`station access application area seems to be based almost
`exclusively on fingerprints, due to the relatively low cost,
`small size, and ease of integration of fingerprint authenti-
`cation devices.
`
`Hand geometry
`Hand geometry involves analyzing and measuring the
`shape of the hand.This biometric offers a good balance of
`performance characteristics and is relatively easy to use.
`It might be suitable where there are more users or where
`users access the system infrequently and are perhaps less
`disciplined in their approach to the system.
`Accuracy can be very high if desired, and flexible per-
`formance tuning and configuration can accommodate a
`wide range of applications. Organizations are using hand
`geometry readers in various scenarios, including time and
`attendance recording, where they have proved extremely
`popular. Ease of integration into other systems and
`processes, coupled with ease of use, makes hand geometry
`an obvious first step for many biometric projects.
`
`Retina
`A retina-based biometric involves analyzing the layer of
`blood vessels situated at the back of the eye. An estab-
`lished technology, this technique involves using a low-
`intensity light source through an optical coupler to scan
`
`Iris
`An iris-based biometric, on the other hand,
`involves analyzing features found in the colored
`ring of tissue that surrounds the pupil. Iris scan-
`ning, undoubtedly the less intrusive of the eye-
`related biometrics, uses a fairly conventional
`camera element and requires no close contact
`between the user and the reader. In addition, it
`has the potential for higher than average tem-
`plate-matching performance. Iris biometrics
`work with glasses in place and is one of the few
`devices that can work well in identification mode.
`Ease of use and system integration have not tra-
`ditionally been strong points with iris scanning
`devices, but you can expect improvements in
`these areas as new products emerge.
`
`Face
`Face recognition analyzes facial characteristics. It
`requires a digital camera to develop a facial image of the
`user for authentication.This technique has attracted con-
`siderable interest, although many people don’t completely
`understand its capabilities. Some vendors have made
`extravagant claims—which are very difficult, if not impos-
`sible, to substantiate in practice—for facial recognition
`devices. Because facial scanning needs an extra peripheral
`not customarily included with basic PCs, it is more of a
`niche market for network authentication. However, the
`casino industry has capitalized on this technology to cre-
`ate a facial database of scam artists for quick detection by
`security personnel.
`
`Signature
`Signature verification analyzes the way a user signs her
`name. Signing features such as speed, velocity, and pressure
`are as important as the finished signature’s static shape.
`Signature verification enjoys a synergy with existing
`processes that other biometrics do not. People are used to
`signatures as a means of transaction-related identity veri-
`fication, and most would see nothing unusual in extending
`this to encompass biometrics. Signature verification devices
`are reasonably accurate in operation and obviously lend
`themselves to applications where a signature is an accepted
`identifier. Surprisingly, relatively few significant signature
`applications have emerged compared with other biomet-
`
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`

`ric methodologies. But if your application fits, it is a tech-
`nology worth considering.
`
`Voice
`Voice authentication is not based on voice recognition
`but on voice-to-print authentication, where complex tech-
`nology transforms voice into text.Voice biometrics has the
`most potential for growth, because it requires no new hard-
`ware—most PCs already contain a microphone. However,
`poor quality and ambient noise can affect verification. In
`addition, the enrollment procedure has often been more
`complicated than with other biometrics, leading to the per-
`ception that voice verification is not user friendly.
`Therefore, voice authentication software needs improve-
`ment. One day, voice may become an additive technology
`to finger-scan technology. Because many people see finger
`scanning as a higher authentication form, voice biometrics
`will most likely be relegated to replacing or enhancing
`PINs, passwords, or account names.
`
`USES FOR BIOMETRICS
`Security systems use biometrics for two basic purposes:
`to verify or to identify users. Identification tends to be the
`more difficult of the two uses because a system must search
`a database of enrolled users to find a match (a one-to-many
`search). The biometric that a security system employs
`depends in part on what the system is protecting and what
`it is trying to protect against.
`
`Physical access
`For decades, many highly secure environments have used
`biometric technology for entry access. Today, the primary
`application of biometrics is in physical security: to control
`access to secure locations (rooms or buildings). Unlike
`photo identification cards, which a security guard must ver-
`ify, biometrics permit unmanned access control. Biometric
`devices, typically hand geometry readers, are in office
`buildings, hospitals, casinos, health clubs, and even a Moose
`lodge. Biometrics are useful for high-volume access con-
`trol. For example, biometrics controlled access of 65,000
`people during the 1996 Olympic Games, and Disney World
`uses a fingerprint scanner to verify season-pass holders
`entering the theme park.
`Engineers are developing several promising prototype
`biometric applications to support the International Air
`Transport Association’s Simplifying Passenger Travel
`(SPT) initiatives. One such program is EyeTicket, which
`Charlotte/Douglas International Airport
`in North
`Carolina and Flughafen Frankfurt/Main Airport in
`Germany are evaluating. EyeTicket links a passenger’s fre-
`quent-flyer number to an iris scan. After the passenger
`enrolls in the system, an unmanned kiosk performs tick-
`eting and check-in (without luggage).
`The US Immigration and Naturalization Service’s
`Passenger Accelerated Service System uses hand geometry
`
`Glossary
`
`Crossover error rate (CER)—a comparison metric for dif-
`ferent biometric devices and technologies; the error rate
`at which FAR equals FRR. The lower the CER, the more
`accurate and reliable the biometric device.
`Enrollment—the initial process of collecting biometric
`data from a user and then storing it in a template for later
`comparison.
`False-acceptance rate (FAR)—the percentage of
`imposters incorrectly matched to a valid user’s biometric.
`False-rejection rate (FRR)—the percentage of incorrectly
`rejected valid users.
`Identification—the process by which the biometric sys-
`tem identifies a person by performing a one-to-many (1:n)
`search against the entire enrolled population.
`Template—a mathematical representation of biometric
`data. A template can vary in size from 9 bytes for hand
`geometry to several thousand bytes for facial recognition.
`Verification—the authentication process by which the
`biometric system matches a captured biometric against
`the person’s stored template (1:1).
`
`to identify and process preenrolled, low-risk frequent trav-
`elers through an automated immigration system.Currently
`deployed in nine international airports, including Washing-
`ton Dulles International, this system uses an unmanned
`kiosk to perform citizenship-verification functions.
`
`Virtual access
`For a long time, biometric-based network and computer
`access were areas often discussed but rarely implemented.
`Recently, however, the unit price of biometric devices has
`fallen dramatically, and several designs aimed squarely at
`this application are on the market. Analysts see virtual
`access as the application that will provide the critical mass
`to move biometrics for network and computer access from
`the realm of science-fiction devices to regular system com-
`ponents.At the same time, user demands for virtual access
`will raise public awareness of the security risks and lower
`resistance to the use of biometrics.
`Physical lock-downs can protect hardware,and passwords
`are currently the most popular way to protect data on a net-
`work. Biometrics, however, can increase a company’s abil-
`ity to protect its data by implementing a more secure key
`than a password. Using biometrics also allows a hierarchi-
`cal structure of data protection, making the data even more
`secure: Passwords supply a minimal level of access to net-
`work data; biometrics, the next level. You can even layer
`biometric technologies to enhance security levels.
`
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`
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`S E C U R I T Y
`
`Resources
`
`The Biometric Consortium (http://www.biometrics.org): Serves as
`the US government’s focal point for research, development, test,
`evaluation, and application of biometric-based personal identifica-
`tion and verification technologies.
`➤ Association for Biometrics (http://www.afb.org.uk): Aims to pro-
`mote the awareness and development of biometric-related tech-
`nologies. It provides an international forum for research and
`development, system design and integration, application develop-
`ment, market development, and other issues.
`➤ Avanti (http://homepage.ntlworld.com/avanti/):A reference site for
`biometrics, Avanti contains a considerable amount of background
`information about biometrics, their use in everyday business situa-
`tions, and how to deploy them.
`Biometrics: Journal of the International Biometric Society (http://
`stat.tamu.edu/Biometrics/): Published quarterly, Biometrics aims to
`promote and extend the use of mathematical and statistical methods
`in various disciplines. It describes and exemplifies developments in
`these methods and their application for experimenters and those
`primarily concerned with data analysis.
`International Biometric Industry Association (http://www.ibia.
`org):A trade association founded in September 1998 in Washington,
`D.C., to advance, advocate, defend, and support the biometric indus-
`try’s collective international interests. Governed by and for biometric
`developers, manufacturers, and integrators, IBIA aims to serve all
`biometric technologies in all applications.
`
`E-commerce applications
`E-commerce developers are exploring the use of bio-
`metrics and smart cards to more accurately verify a trad-
`ing party’s identity. For example, many banks are
`interested in this combination to better authenticate cus-
`tomers and ensure nonrepudiation of online banking, trad-
`ing, and purchasing transactions. Point-of-sales (POS)
`system vendors are working on the cardholder verification
`method, which would enlist smart cards and biometrics to
`replace signature verification. MasterCard estimates that
`adding smart-card-based biometric authentication to a
`POS credit card payment will decrease fraud by 80 per-
`cent.
`Some are using biometrics to obtain secure services over
`the telephone through voice authentication. Developed by
`Nuance Communications, voice authentication systems are
`currently deployed nationwide by both the Home Shopping
`Network and Charles Schwab.The latter’s marketing catch
`phrase is “No PIN to remember, no PIN to forget.”
`
`Covert surveillance
`One of the more challenging research areas involves
`using biometrics for covert surveillance. Using facial and
`
`30
`
`IT Pro January ❘ February 2001
`
`re-
`body recognition technologies,
`searchers hope to use biometrics to auto-
`matically
`identify known suspects
`entering buildings or traversing crowded
`security areas such as airports.The use of
`biometrics for covert identification as
`opposed to authentication must over-
`come technical challenges such as simul-
`taneously identifying multiple subjects in
`a crowd and working with uncooperative
`subjects. In these situations, devices can-
`not count on consistency in pose, view-
`ing angle, or distance from the detector.
`
`THE FUTURE OF BIOMETRICS
`Although companies are using bio-
`metrics for authentication in a variety of
`situations, the industry is still evolving
`and emerging. To both guide and sup-
`port the growth of biometrics, the
`Biometric Consortium
`formed
`in
`December 1995. The recent Biometric
`Consortium annual conference high-
`lighted two important areas.
`
`Standardization
`The biometrics industry includes more
`than 150 separate hardware and soft-
`ware vendors, each with their own pro-
`prietary interfaces, algorithms, and data
`structures. Standards are emerging to
`provide a common software interface, to
`allow sharing of biometric templates, and to permit effec-
`tive comparison and evaluation of different biometric
`technologies.
`The BioAPI standard released at the conference, defines
`a common method for interfacing with a given biometric
`application. BioAPI is an open-systems standard devel-
`oped by a consortium of more than 60 vendors and gov-
`ernment agencies. Written in C, it consists of a set of
`function calls to perform basic actions common to all bio-
`metric technologies, such as
`
`• enroll user,
`• verify asserted identity (authentication), and
`• discover identity.
`
`Not surprising, Microsoft, the original founder of the
`BioAPI Consortium, dropped out and developed its own
`BAPI biometric interface standard.
`Another draft standard is the Common Biometric
`Exchange File Format, which defines a common means of
`exchanging and storing templates collected from a variety
`of biometric devices. The Biometric Consortium has also
`presented a proposal for the Common Fingerprint Minutia
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`➤
`➤
`➤
`

`

`Table 1. Comparison of biometrics
`
`Fingerprints
`High
`Dryness, dirt,
`age
`High
`*
`Medium
`
`Characteristic
`Ease of Use
`Error incidence
`
`Accuracy
`Cost
`User acceptance
`Required
`High
`security level
`Long-term stability High
`
`Hand geometry
`High
`Hand injury,
`age
`High
`*
`Medium
`
`Retina
`Low
`Glasses
`
`Very high
`*
`Medium
`
`Iris
`Medium
`Poor
`lighting
`Very high
`*
`Medium
`
`Face
`Medium
`Lighting, age,
`glasses, hair
`High
`*
`Medium
`
`Signature
`High
`Changing
`signatures
`High
`*
`Very high
`
`Voice
`High
`Noise, colds,
`weather
`High
`*
`High
`
`Medium
`Medium
`
`High
`High
`
`Very high Medium
`High
`Medium
`
`Medium
`Medium
`
`Medium
`Medium
`
`* The large number of factors involved makes a simple cost comparison impractical.
`
`Exchange format, which attempts to provide a level of
`interoperability for fingerprint technology vendors.
`Biometric assurance—confidence that a biometric
`device can achieve the intended level of security—is
`another active research area. Current metrics for com-
`paring biometric technologies, such as the crossover error
`rate and the average enrollment time, are limited because
`they lack a standard test bed on which to base their val-
`ues. Several groups, including the US Department of
`Defense’s Biometrics Management Office, are developing
`standard testing methodologies. Much of this work is
`occurring within the contextual framework of the
`Common Criteria, a model that the international security
`community developed to standardize evaluation and com-
`parison of all security products (Kimberly Caplan,
`“Building an International Security Standard,” IT
`Professional, Mar.-Apr. 1999).
`
`Hybrid technology uses
`One of the more interesting uses of biometrics involves
`combining biometrics with smart cards and public-key
`infrastructure (PKI). A major problem with biometrics is
`how and where to store the user’s template. Because the
`template represents the user’s personal characters, its stor-
`age introduces privacy concerns. Furthermore, storing the
`template in a centralized database leaves that template
`subject to attack and compromise. On the other hand, stor-
`ing the template on a smart card enhances individual pri-
`vacy and increases protection from attack, because
`individual users control their own templates.
`Vendors enhance security by placing more biometric func-
`tions directly on the smart card. Some vendors have built a
`fingerprint sensor directly into the smart card reader,which
`in turn passes the biometric to the smart card for verifica-
`tion.At least one vendor,Biometric Associates,has designed
`
`a smart card that contains a fingerprint sensor directly on
`the card.This is a stronger secure architecture because card-
`holders must authenticate themselves directly to the card.
`PKI uses public- and private-key cryptography for user
`identification and authentication. It has some advantages
`over biometrics: It is mathematically more secure, and it
`can be used across the Internet.The main drawback of PKI
`is the management of the user’s private key.To be secure,
`the private key must be protected from compromise; to be
`useful, the private key must be portable. The solution to
`these problems is to store the private key on a smart card
`and protect it with a biometric.
`In the Smart Access common government ID card pro-
`gram, the US General Services Administration is explor-
`ing this marriage of biometrics, smart cards, and PKI
`technology. The government of Finland is also consider-
`ing using these technologies in deploying the Finnish
`National Electronic ID card.
`
`SELECTING A BIOMETRIC TECHNOLOGY
`Biometric technology is one area that no segment of the
`IT industry can afford to ignore. Biometrics provide secu-
`rity benefits across the spectrum, from IT vendors to end
`users, and from security system developers to security sys-
`tem users.All these industry sectors must evaluate the costs
`and benefits of implementing such security measures.
`Different technologies may be appropriate for different
`applications, depending on perceived user profiles, the
`need to interface with other systems or databases, envi-
`ronmental conditions, and a host of other application-spe-
`cific parameters (see Table 1).
`
`Ease of use
`Some biometric devices are not user friendly. For exam-
`ple, users without proper training may experience diffi-
`
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`S E C U R I T Y
`
`• biometric capture hardware;
`• back-end processing power to maintain the database;
`• research and testing of the biometric system;
`• installation, including implementation team salaries;
`• mounting, installation, connection, and user system inte-
`gration costs;
`• user education, often conducted through marketing
`campaigns;
`• exception processing, or handling users who cannot sub-
`mit readable images because of missing appendages or
`unreadable prints;
`• productivity losses due to the implementation learning
`curve; and
`• system maintenance.
`
`User acceptance
`Generally speaking, the less intrusive the biometric, the
`more readily it is accepted. However, certain user groups—
`some religious and civil-liberties groups—have rejected
`biometric technologies because of privacy concerns.
`
`Figure 2. Crossover error rate
`attempts to combine two
`measures of biometric accuracy.
`
`Crossover error rate
`
`False-acceptance rate
`
`False-rejection rate
`
`0
`
`culty aligning their head with a device for enrolling and
`matching facial templates.
`
`Error incidence
`Two primary causes of errors affect biometric data: time
`and environmental conditions. Biometrics may change as
`an individual ages. Environmental conditions may either
`alter the biometric directly (for example, if a finger is cut
`and scarred) or interfere with the data collection (for
`instance, background noise when using a voice biometric).
`
`Required security level
`Organizations should determine the level of security
`needed for the specific application: low, moderate, or high.
`This decision will greatly impact which biometric is most
`appropriate. Generally, behavioral biometrics are suffi-
`cient for low-to-moderate security applications; physical
`biometrics, for high-security applications.
`
`Accuracy
`Vendors often use two different methods to rate bio-
`metric accuracy: false-acceptance rate or false-rejection
`rate. Both methods focus on the system’s ability to allow
`limited entry to authorized users. However, these meas-
`ures can vary significantly, depending on how you adjust
`the sensitivity of the mechanism that matches the bio-
`metric. For example, you can require a tighter match
`between the measurements of hand geometry and the
`user’s template (increase the sensitivity).This will proba-
`bly decrease the false-acceptance rate, but at the same time
`can increase the false-rejection rate. So be careful to
`understand how vendors arrive at quoted values of FAR
`and FRR.
`Because FAR and FRR are interdependent, it is more
`meaningful to plot them against each other, as shown in
`Figure 2. Each point on the plot represents a hypothetical
`system’s performance at various sensitivity settings. With
`such a plot, you can compare these rates to determine the
`crossover error rate. The lower the CER, the more accu-
`rate the system.
`Generally, physical biometrics are more accurate than
`behavioral biometrics.
`
`Cost
`Cost components include
`
`32
`
`IT Pro January ❘ February 2001
`
`Long-term stability
`Organizations should consider a biometric’s stability,
`including maturity of the technology, degree of standard-
`ization, level of vendor and government support, market
`share, and other support factors. Mature and standardized
`technologies usually have stronger stability.
`
`B iometric technology has been around for decades
`
`but has mainly been for highly secretive environ-
`ments with extreme security measures. The tech-
`nologies behind biometrics are still emerging. This article
`gives a snapshot of the dynamics under way in this emerg-
`ing biometric market, and we hope it will help you con-
`sider all the possible alternatives when acquiring new
`biometric technologies. I
`
`Simon Liu is director of computer and communications
`systems at the National Library of Medicine. He is also an
`adjunct professor at Johns Hopkins University. Contact him
`at simon_liu@nlm.nih.gov.
`
`Mark Silverman is a technical advisor at the Center of
`Information Technology, National Institutes of Health. Con-
`tact him at mls@nih.gov.
`
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`