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It is to the benefit of both a smart card owner and a smart card issuer that the identity of the cardholder is confirmed before the card is used. Before both parties transact business, they must be assured of the identity of the other party.

When we meet in person, we use visual and verbal clues to help us to recognize the other party. With electronic communication, we use encryption technology to unambiguously verify that the other person is who they may claim to be.

2.7.1 PIN Codes

A Personal Identification Code (PIN) is usually a four or five-digit number that accompanies a smart card and must be memorized by the cardholder. The PIN is stored securely within the smart card in a way that can never be read from the external world. Data and functions on the smart card can be protected in a way that access from the external world is allowed only after the correct PIN code is presented. The IBM MFC can store up to two PIN codes per application but normally only one PIN code is required. This simplifies the user interface. It is possible to program the second PIN code as an administrator PIN code. For

example, this would be used to unblock the card in case the user either forgot the first PIN code or entered the code incorrectly too many times in sequence.

The PIN can be assigned and stored in the card during personalization. The application program can supply the PIN code in two different ways. If the user has an intelligent smart card reader attached (for example a smart card reader with a keyboard and display), then the application can ask the smart card reader to display the password prompt and accept the user′s input. If the user has a simple smart card reader attached, then the PIN code can be entered from within the application program itself and send to the smart card reader.

With the profusion of smart card applications, people are required to remember more and more PIN numbers. This puts a strain on the user′s memory. After all, who can remember 15 or 20 different PIN codes? Sometimes, people jot down the PIN number on the card itself as a means to jog their memory. This is dangerous as it nullifies the advantage of having the PIN in the first place. That is why recent emphasis on security measures have revolved around biometric measurement techniques as a means of identifying a person.

2.7.2 Biometrics

Biometrics is the science and technology of measuring human biological features to unambiguously identify an individual within a group of people. One of the driving forces behind the development of biometric identification

technology is the reluctance within the user community to memorize passwords and PIN numbers for identification. Also, a PIN number does not uniquely identify an individual because PIN numbers can be shared among different people (sometimes inadvertently when people write their PIN numbers on the card itself and then lose the card). Biometrics identify the actual person and not the person′s knowledge of a shared secret.

Some of the biological features that are both unique to an individual and that can be measured are:

Signatures and fingerprints are two techniques that have been known for hundreds of years. Both techniques are in popular use, the latter most often associated with police identification. Using machines to automate the analysis is relatively new.

Fingerprint analysis is based on mathematical relationships in the direction of cutpoints through the minutia, the lines in your finger. The set of minutia vectors (that is, the number and direction of cutpoints) for an individual are unique for each and every individual. A precompiled minutia vector database can be stored on the smart card because the data takes up very little space,

approximately 300-800 bytes. The fingerprint scanned at the biometric station can be mathematically compared to the reference and a statistically good match will be accepted as that individual.

Hand geometry is a biometric technique that uses features of the size and shape of the person′s hand to uniquely single out a person from a group. The

recognition speed is relatively fast. Also, the size of the reference pattern is small, normally 10-30 bytes, so it can easily be stored onto a smart card. The main limitation of hand geometry recognition is that the group size must be small. This technique is usually employed for facilities access where the total number of people to be allowed access is relatively small, a few dozen at the most.

The pattern of blood vessels on the back of the eye retina is also, like a fingerprint, unique in each person. A low-power laser can scan the retina and record the pattern. Like a fingerprint analysis system, the pattern of the retina can be compared to a statically stored pattern on the card and a match will authenticate the individual.

Today, smart cards contain reference data that will be used by the biometric station. The biometric station will compare the dynamic data obtained from the biological feature to the reference data stored in the smart card. The

comparison is done on the biometric station and not within the smart card itself.

Thus, the security of the system is dependent on the security of the biometric station itself. For example, if a fingerprint sensor is built into a computer station keyboard, the security of the system is no better than the preventative measures in place to prevent tampering with the keyboard and its connecting wires.

Table 1. Comparison of Biometric K e y Factors Acceptance Cost of

The IBM Smart Card Development Group assembled Table 1 to compare several factors of the various traditional and biometric identification methods. Let′s clarify the table columns:

Acceptance Acceptability in the user community for using this identification method. The percentage figure in the table is a probability that a user of the system would accept that technology and use it. Of course, the acceptance rate is only approximate because social factors, country of origin, age and so on will affect these numbers.

Generally, a higher number is better.

Cost of Enrollment The ″price of admission″ or the initial investment that a company must make for this technology.

Rejects The probability of false refusal. This figure is a probability that the device will reject an attempt by an authorized user to use the system.

A lower number is better.

Substitutions The probability of false acceptance. This figure is a probability that an unauthorized user will be accepted by the device instead of being rejected. A lower number is better.

File Size The approximate number of bytes that a reference file would occupy on the smart card. Obviously, a lower number is better, at least in terms of smart card memory consumption.

Device Cost The relative unit price in large quantities.

It is probable that biometric techniques will be used in concert with PIN code entry. There are legal reasons for this. Entering a PIN code at a card terminal is more than a means to identify an individual; it is a consent by the person entering the PIN to the operator of the smart card application that he/she agrees to the terms and conditions of the transaction. It is inconceivable that scanning a person′s retina from some distance as that person passes by a sensor is considered a form of consent by that person, in a legal sense.

Biometrics standards are being developed by the BioAPI Consortium (http://www.bioapi.org), but this effort is just starting as this entity was established in April of 1998.

2.7.3 Mutual Authentication

The smart card application and smart card are able to verify the identity of each other automatically when the smart card is inserted into the smart card reader.

This automatic check is performed without explicit input from the user but involves the same concepts discussed above with PIN codes. A smart card application designer would want to do this so that the smart card can verify that it has not been plugged into a hostile smart card reader for the purpose of being attacked (this is called internal authentication). Conversely, a smart card

reader′s secure application module (SAM) or application program on the host can verify that a smart card that it has detected is an authentic smart card (this is called external authentication).

This is an example of the process of mutual authentication. Before Bob sends any messages to Alice, Bob sends a random number to Alice. Alice encrypts the random number using the DES key that Alice has previously stored and returns the enciphered text back to Bob. Bob decrypts the enciphered text. If the random number Bob decrypts is the same as the number that was sent to Alice, then Bob knows that Alice shares the same DES key.

If both the smart card application and smart card authenticate each other in one process, that process is called ″mutual symmetric authentication″. In some cases, such as when the smart card lacks the ability to do RSA encryption or the smart card reader is offline, only the smart card reader will authenticate the smart card based on signed data preprogrammed into the smart card at personalization. This process of one-way authentication is called ″static asymmetrical authentication″.