Abstract of this communication paper-presentaations : (Global Positioning System)
The physical and logical structure of the smart card and the corresponding security access control has been discussed in this paper. It is believed that smart cards offer more security and confidentiality than the other kinds of information or transaction storage. Moreover, applications applied with smart card technologies are illustrated which demonstrates smart card is one of the best solutions to provide and enhance their system with security and integrity.
Today, smart cards are being used in different areas as they can be used together with other technologies, such as asymmetric cryptographic algorithms, biometrics identification and to provide highly assured and trusted applications. This paper discusses three particular areas where demonstrated how different systems can make use of the smart card to enhance their securities.
At the end of the paper, an overview of the attack techniques on the smart card is discussed as well. Having those attacks does not mean that smart card is insecure. It is important to realize that attacks against any secure systems are nothing new or unique. Any systems or technologies claiming 100% secure are impossible. The main consideration of determining whether a system is secure or not depends on whether the level of security can meet the requirement of the system.
1.Introduction
Definition:
A smart card resembles a credit card in size and shape, but inside it is completely different. The inside of a smart card usually contains an embedded microprocessor. The microprocessor is under a gold contact pad on one side of the card. It provides not only memory capacity, but computational capability as well. The self-containment of smart card makes it resistant to attack as it does not need to depend upon potentially vulnerable external resources. Because of this characteristic, smart cards are often used in different applications which require strong security protection and authentication.
For examples, smart card can act as an identification card which is used to prove the identity of the card holder. It also can be a medical card which stores the medical history of a person. Furthermore, the smart card can be used as a credit/debit bank card which allows off-line transactions. All of these applications require sensitive data to be stored in the card, such as biometrics information of the card owner, personal medical history, and cryptographic keys for authentication, etc.
In the near future, the traditional magnetic strip card will be replaced and integrated together into a single card by using the multi-application smart card, which is known as an electronic purse or wallet in the smart card industry. The smart card is becoming more and more significant and will play an important role in our daily life. It will be used to carry a lot of sensitive and critical data about the consumers ever more than before when compared with the magnetic strip card. Therefore, there are many arguments and issues about whether or not the smart card is secure and safe enough to store that information. This has always been a source of controversy.
2. Physical Structure
The physical structure of a smart card is specified by the International Standards Organization (ISO) 7810, 7816/1 and 7816/2. The plastic card is the most basic one and has the dimensions of 85.60mm x 53.98mm x 0.80mm. A printed circuit and an integrated circuit chip are embedded on the card. Figure 1 shows an overview of the physical structure of a smart card.
The printed circuit conforms to ISO standard 7816/3 which provides five connection points for power and data. The printed circuit protects the circuit chip from mechanical stress and static electricity. Communication with the chip is accomplished through contacts that overlay the printed circuit.
The capability of a smart card is defined by its integrated circuit chip. Typically, an integrated circuit chip consists of a microprocessor, read only memory (ROM), non static random access memory (RAM) and electrically erasable programmable read only memory (EEPROM) which will retain its state when the power is removed.
3. Life Cycle of a Smart Card
There is an operating system inside each smart card which may contain a manufacturer identification number (ID), type of component, serial number, profile information, and so on. More important, the system area may contain different security keys, such as manufacturer key or fabrication key (KF), and personalization key (KP). All of this information should be kept secret and not be revealed by others.
Hence, from the manufacturer to the application provider, then the card holder, the production of a smart card is divided into different phases. Limitation on transfer and access of data is incremental at different phases in order to protect different areas in the smart card. There are five main phases for a typical smart card life cycle. We will discuss each of them below.
3.2.1 Fabrication Phase
This phase is carried out by the chip manufacturers. The silicon integrated circuit chip is created and tested in this phase. A fabrication key (KF) is added to protect the chip from fraudulent modification until it is assembled into the plastic card support. The KF of each chip is unique and is derived from a master manufacturer key. Then the chip is ready to deliver to the card manufacturer with the protection of the key KF.
3.2.2 Pre-personalization Phase
This phase is carried out by the card suppliers. In this phase, the chip will be mounted on the plastic card. The connection between the chip and the printed circuit will be made, and the whole unit can be tested. For added security and to allow secure delivery of the card to the card issuer, the fabrication key will be replaced by a personalization key (KP). After that, a personalization lock VPER will be written to prevent further modification of the KP. Access of the card can be done only by using logical memory addressing. This preserves the system and fabrication areas being accessed or modified.
3.2.3 Personalization Phase
This phase is conducted by the card issuers. It completes the creation of logical data structures. Data files contents and application data are written to the card. Information of card holder identity, PIN, and unblocking PIN will be stored as well.
3.2.4 Utilization Phase
This is the phase for the normal use of the card by the card holder. The application system, logical file access controls, and others are activated. Access of information on the card will be limited by the security policies set by the application.
3.2.5 End-of-Life Phase (Invalidation Phase)
There are two ways to move the card into this phase. One is initiated by the application which writes the invalidation lock to an individual file or the master file. All the operations including writing and updating will be disabled by the operating system. Only read instructions may remain active for analysis purposes.
4. Logical Structure and Access Controls
After a smart card is issued to the consumer by the application provider, the protection of the card will be controlled by the application operating system mainly. Physical addressing mode of accessing data is no longer available. Access of data has to be done through the logical file structure on the card. This section will discuss how the operating system accomplishes the security protection of the data stored on the card by examining the logical file structure and the corresponding access controls of a smart card.
4.1 Logical File Structure
In general, in terms of data storage, a smart card can be viewed as a disk drive where files are organized in a hierarchical form through directories. Similar to MS-DOS, there is one master file (MF) which is like the root directory. Under the root, we can have different files which are called elementary files (EFs). We can also have various subdirectories called dedicated files (DFs). Under each subdirectory will be elementary files again. The main difference of a smart card file structure and a MS-DOS file structure is that dedicated files can also contain data.
In smart card terminology, the root or master file (MF), besides the header part which consists of itself, the body part contains the headers of all of the dedicated files and elementary files which contain the MF in their parental hierarchy. The dedicated file (DF) is a functional grouping of files consisting of it and all the files which are immediate Childs of the DF. The elementary file (EF) simply consists of its header and the body which stores the data.
The ways that the data is managed within a file differ and are dependent on different operating systems. Some of them may manage the data simply by offset and length, while the others may organize data in fixed or variable lengths of records such as Global System for Mobile Communication (GSM) system. In any cases, the file must be selected before performing any operations. This is equivalent to opening a file.
The logical access and selection mechanisms are activated after the power is supplied to the card while the master file is selected automatically. The selection operation allows movement around the tree. It can be descending by selecting an EF or a DF, or it can be ascending by selecting a MF or DF. Horizontal movement can be done by selecting an EF from another EF as well.
After the success of selection, the header of the file can be retrieved, which stores the information about the file such as identification number, description, types, size, and so on. Particularly, it stores the attribute of the file which states the access conditions and current status. Access of the data in the file depends on whether those conditions can be fulfilled or not.
4.2 Access Control
The smart card access control system covers file access mainly. Each file is attached by a header which indicates the access conditions or requirements of the file and the current status as well. The fundamental principle of the access control is based on the correct presentation of PIN numbers and their management.
5. Procedural Protection
After an overview of the physical and logical protection given by the smart card, its time to look at how we can make use of the smart card to protect and secure our systems in the real life.
Because of the on-board computing power of the smart card, it is possible to achieve off-line transactions and verifications. For instance, a smart card and a card acceptor device (CAD) can identify each other by using the mutual active authentication method. Moreover, data and codes stored on the card are encrypted by the chip manufacturer by using computational scrambling encryption, which makes the circuit chip almost impossible to be forged. All of these features together with the protected access control are discussed in the previous section.
Today, smart cards are being used in different areas because they can be used together with other technologies, such as asymmetric cryptographic algorithms and biometrics identification, to provide highly assured and trusted applications. This section discusses three particular areas where demonstrated how different systems can make use of the smart card to enhance their securities.
5.1 Identification of Documents
Traditional document based identifications, such as identification card, licenses, passport/visa, and so on, are always considered unreliable. All of them are easy to be forged and copied. Particularly with today’s technologies, high quality color photocopies, printers, and scanners are easily accessed and owned, as a result high quality fraudulent documents can be produced easily. This makes the inspection of documents more and more difficult.
The smart card probably is the best solution to solve this problem. Printed information and photographs can be digitized and stored into the card. By setting up the access condition and password on files, only authorized persons or authorities, such as government departments, are allowed to access the information. Moreover, together with the biometrics technology, biometrics information of the card holder can be placed on the card, so that the smart card can corporate with biometrics scanner to identify or verify whether the card is owned by the card holder or not. This significantly improves the reliability of the document the smart card carries.
Here instead of verifying the documents by observation of an inspection officer, a card acceptor device will be used. The device which contains the authorized code and PIN can unlock the file and retrieve the owner’s information for verification.
5.2 Authentication through Kerberos Server
In an open distributed computing environment (DCE), to protect a system from being attacked by remote network hosts, a certain kind of authentication must be taken into account.
Kerberos is one of the systems which provide trusted third-party authentication services to authenticate users on a distributed network environment. Basically, when a user or client requests an access to a particular service from the server, he/she has to obtain a credential from the Kerberos authentication server (AS). The user then presents that credential to the Authentication Granting server (AGS) and obtains a service. Hence, the user can request for service by submitting the service credentials to the desired server. Figure 3 shows this authentication protocol.
An attacker can obtain the credential of another user, and perform off-line attack by using a password guessing approach. This security weakness of Kerberos is pointed out by Mark and Gary (1995) in one of their papers "Integrating Smart Card In to Authentication Systems".
In their report, they proposed to integrate the smart card into the Kerberos system to overcome this problem.
5.3 Access Control on Operating System
Access control is one of the important usages of the smart card technology. It is also the motivation behind the development of smart card. In this section, we discuss how to control the access of an operating system in a personal computer by using the smart card.
The single-user nature of personal computers is lack of security protection on their system, especially the system areas such as the boot sector of a hard disk or floppy. They are allowed to be modified by anyone without any protection; this causes the possibility of infection by computer virus. In the present days, a personal computer is powerful enough to take the place of mini-computers to act as a network server, but its single-user nature has not changed and this has caused the problem to become more serious.
A boot integrity token system (BITS) is introduced by Paul and Lance who make use of smart card technology to protect the operating system. The basic idea is that the host computer is booted actually from a smart card or it requires critical information from the card to complete the boot sequence. So that even if an attacker can gain physical access to the hardware, it is impossible to guarantee system integrity.
The smart card is configured to require user authentication prior to the data access. During system startup, two authentications have to be performed before the completion of boot sequence. At first, the user is authenticated to the smart card by means of a password. And then the host authenticates the card by reading the shared secret from the card. After both of them are matched, host reads boot section information from the smart card and completes the boot sequence. Then the PC operates as normal.
The smart card can also store the checksum of critical data and executable programs. It is effective against virus by validating files integrity rather than scan for known virus signatures. In general, the use of smart card here enhanced the security of the computer by utilizing the inherent secure storage and processing capabilities.
6. Attacks on Smart Card
As discussed in all above, the smart card seems to be a superior tool for enhancing system security and provides a place for secure storage. One of the security features provided by most of the smart card operating systems, which is not mentioned in this paper, is the cryptographic facilities. They provide encryption and decryption of data for the card; some of them can even be used to generate cryptographic keys.
The secret of the cryptographic algorithm, the keys stored, and the access control inside the smart card become the targets of attackers. Nowadays many companies and cryptographers claim to be able to break the smart card and its microcontroller. Some of them perform logical non-invasive attacks; some of them attack the card physically while others just prove their success by mathematical theorems.
We will review the first two briefly and examine how the attacks are achieved. For the third one, since their attacks are theoretical and relate to a lot of complicated mathematical calculations and formulas which are outside the scope of this paper, it is not discussed here.
6.1 Logical Attacks
As all the key material of a smart card is stored in the electrically erasable programmable read only memory (EEPROM), and due to the fact that EEPROM write operations can be affected by unusual voltages and temperatures, information can be trapped by raising or dropping the supplied voltage to the microcontroller. In the report of "Tamper Resistance - A Cautionary Note" by Ross and Markus (1996), several examples of attacking the smart card microcontroller by adjusting the voltage are provided.
For example, a widely known attack of PIC16C84 microcontroller is that the security bit of the controller can be clear with erasing the memory by raising the voltage VCC to VPP - 0.5V. An attack on DS5000 security processor is another example. A short voltage drop can release the security lock without erasing the secret data sometimes. Low voltage can facilitate other attacks as well; such as an analogue random generator used to create cryptographic keys will produce an output of almost all 1’s when the supply voltage is lowered slightly.
For these reasons, some security processors implemented sensors which will cause an alarm when there is any environmental change. However, these kinds of sensors always cause false alarm due to the occurrence of fluctuations when the card is powered up and the circuit is stabilizing. Therefore this scheme is not commonly used.
6.2 Physical Attacks
Invasive physical attacks are typical. Before this kind of attack can be performed, the circuit chip has to be removed from the plastic card. This can be done by simply using a sharp knife to cut away the plastic behind the chip module until the epoxy resin becomes visible. And then the resin can be dissolved by adding a few drops of fuming nitric acid (>98% HNO3). The acid and resin can be washed away by shaking the card in acetone until the silicon surface is fully exposed. Ultimately the chip can be examined and attacked directly.
At Cavendish laboratory in Cambridge, a technique is developed for reverse engineering the circuit chips. The layout and function of the chip can be identified using that technique. Then another technique developed by IBM can be used to observe the operation of the chip. As a result its secret can be fully revealed.
Besides this, there are many different ways to perform physical attacks. For instance, erasing the security lock bit by focusing UV light on the EPROM, probing the operation of the circuit by using micro probing needles, or using laser cutter microscopes to explore the chip, and so on. However, these kinds of attacks are only available for well funded laboratories as the costs associated are considerably high.
7. Conclusion
Finally, it is concluded that the smart card is an intrinsically secure device. It is a safe place to store valuable information such as private keys, account numbers, and valuable personal data such as biometrics information. The smart card is also a secure place to perform off-line processes such as public or private key encryption and decryption. The smart card can be an element of solution to a security problem in the modern world.
8. References
www.smartcardgroup.com
www.smartcard.uk
www.electronics.howstuffworks.com
www.securingjava.com
www.smartcard.uk
www.electronics.howstuffworks.com
www.securingjava.com