The use of contactless IC cards is extremely extensive. Due to their different backgrounds and target market positioning, the non-contact IC cards introduced by different manufacturers have different characteristics. The current non-contact IC cards can be divided into RF cards and contactless logic encryption cards. Contactless CPU card, hybrid card, and composite card. Among them, the contactless logical encryption card should be the preferred product in the enterprise user selection. The security of the smart card system is an important indicator that must be paid attention to. For many non-contact logical encryption cards, different manufacturers have different security designs. The security levels vary widely. In Figure 1, the SM module in the reader transmits a random number through the antenna. When the proximity card enters the receiving range of the antenna and receives the random number transmitted by the SM module, the random number is encrypted with the password in the card. And return the result to the SM module. The SM module reverses the result returned by the proximity card with the original number, and then confirms the legality of the proximity card. The process of authenticity authentication also generates a new password for all subsequent communication data. Encryption This encryption method uses different random numbers as part of the encryption key each time, which increases the difficulty of cracking and avoids the possibility of fraudulent use of communication data. The process by which the SM module obtains an authorization password is called the authorization of the SM module. As mentioned above, only the authorized module can read and write the corresponding proximity card, so the authorization of the module is equivalent to the download of the system key. The authorization password is stored in the EEPROM of the SM module. For the application, these passwords are not writable, but can be read and deleted. The writing of the authorization password can only be done by reading the "SM authorization card" under the control of the SM module, as shown in Figure 3. A blank card that has not been initialized, the authorization password in the card is blank. Any SM module can read and write the card, so the card must be initialized, that is, the security parameters such as the authorization password, read protection, and write protection of the defined card are different from those of other IC cards. The initialization of the LEGIC contactless IC card must be Under the control of the dedicated authorization module (MSM), before the MSM module initializes the blank card, it must obtain the authorization of the high-level authorization card, and the initialized card must inherit the authorization password of the authorization card as part of its authorization password. For example, to generate a new card with an authorization password of "3824A034", you must obtain an authorization card with an authorization password of "3824". The newly generated card becomes the "subordinate" of its authorization card, as shown in Figure 5. Since the security of the LEGIC system mainly depends on the SM/MSM module, and all authorizations are controlled by the card, it is important to keep the authorization card and the authorized module in order to avoid the loss of authorization. Appropriate precautions can be taken in the application system. In practical applications, the key information stored in the IC card can be encrypted. For example, in the electronic wallet system, the amount item is encrypted by using an authentication algorithm, and the chip number is used as a part of the key to prevent the card from being illegally copied. An example of an authentication algorithm is the DAS (Decimal shift and add) algorithm, by which an authentication code operation for an amount can be described as: The antenna sensing range of the incoming card reader is delayed for a period of time, and the non-contact IC card is powered on and resets, and enters a pause state. In this state, the request response command sent by the card reader can be received when the card is connected to the card reader. After the request response command, the type number of the card is returned, and then the card reader sends an anti-collision command, and the system enters an anti-collision loop. After the anti-collision loop ends, the card reader issues a card selection command, and selects one of the cards. In the stage, the non-contact IC card is in the ready state, and the selected card is then activated. In the activation state, the non-contact IC card receives the mutual authentication command sent by the card reader, and checks the legality of both parties. If the authentication is passed, The next step of reading, writing, adding, subtracting, etc. can be performed. After the above operation is completed, the card reader sends a stop command, and the non-contact IC card returns from the active state to the pause state, and the transaction ends by reading and writing the data in the card. Before the operation, the process from request response to mutual authentication is required. If an error occurs during this process, the read and write operations will not be able to perform the above operations. The finite state machine controlled by the finite state machine receives and recognizes the instructions of the card reader on the one hand, and analyzes the current working state on the other hand, and finds that the conditions specified by the execution of the instruction are met, and if the operation specified by the card reader is performed, The instruction does not satisfy the conditions of execution. The finite state machine sends the control card an error message to the reader and returns the working status to the pause state. If the card reader wants to operate the card again, only from the beginning until all the steps satisfy the condition. And execute it. 3 LEGIC non-contact IC card network composition and its application When applied in the campus, the card management center server is attached to the campus network and interacts with other parts of the system. It is the core of the campus part of the campus card system; the school communication front-end machine is mainly used for the campus network part and the banking part of the card system. Information exchange; each system through the RS485 network cluster through the campus network with TCP / IP protocol and card management center server for information exchange computer room toll system through the computer room toll machine through the campus network and card management center server interaction information school store, activity center, bathroom Discretionary charging points such as entertainment centers, directly connected to the card management center's network card through the RS485 network; installed on the campus's storage machine, connected to the bank and school card management center or financial center, school school management and other management systems Connect directly to the Card Management Center server through the campus network. Conclusion
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LEGIC has many years of experience in security product design, so its non-contact IC card is based on its unique security concept and patented technology. It is the leader in its class. Other similar products have been deciphered. The report, and LEGIC has not yet been, so high security is a major feature of non-contact IC cards. This paper analyzes this and studies its application in campus network.
1. Analysis of LEGIC non-contact IC card security mechanism
The LEGIC security module SM05-S contains highly integrated circuit components, including the RF carrier circuit part, which can complete the transmission of electromagnetic energy and superimpose the digital signal on the LEGIC data carrier to receive signal data from the data carrier; the digital circuit part can Performing encryption, decryption, modulation, and demodulation on the transmitted data, and transmitting and transmitting different interface data signals to the application computer or the micro-processing controller, so that complex concept of confidentiality of the application system, such as authentication, authorization, data organization concept, and reading, can be realized. Write protection and system settings, etc. In the system, the process of establishing communication between the reader (WRU) and the proximity card (MIM) and the actual data communication process are all using a strict encryption algorithm. When the proximity card enters the antenna of the reader Range, the card reader automatically performs the process of mutual authentication, as shown in Figure 1. .jpg)
Figure 1 LEGIC reader certification process
The access control related parameters in the LEGIC contactless IC card are mainly: write protection WRP, which defines a non-writable byte space read protection bit RD, which is set to prevent unauthorized readers from reading. The information in the card; the authorization password, which is used to check the authorization password in the module to confirm the module's read and write permissions to the card.
The reader's approval of the read/write permission of the proximity card is automatically performed by the software solidified in the dedicated module (ASIC) of the SM module, and is not controlled by the application software. Generally, the module must have an authorization password authorization matching the authorization password in the proximity card to read and write the card. As shown in Figure 2, the matching means that the passwords are completely equal or the beginning of the authorization password in the SM module. The same password in the card clears all authorizations of the module .jpg)
Figure 2 reader to the card reading and writing certification diagram
The cancellation of authorization can be carried out in 1 software mode in three ways, that is, the application can delete the authorization password in the SM module by instruction; 2, the card reading mode, like the authorization of the SM module, can be used with the card to cancel the authorization card. Authorization password matching authorization, as shown in Figure 4; 3 hardware mode, SM module has an authorization password clearing end, when the SM power-on reset, if the termination is low, the reset process will clear all authorizations of the module . .jpg)
Figure 3 Authorization and deauthorization of the SM module .jpg)
Figure 4 Schematic diagram of SM deauthorization
The LEGIC contactless IC card system provides users with a complete security system. All access control is done by the firmware in the module. The application does not need to save the system's read and write passwords, even if the application is not broken. The security of the system is controlled by the authorization card due to the authorization of the module and the initialization of the card. Therefore, even if the authorization password of the system is known, and there is no corresponding authorization card, the card of the system or the pseudo card can not be read or written. .jpg)
Figure 5 IC card initialization diagram
Authentication code = DAS (amount, key + chip number)
Through the identification of the authentication code, the reader can identify the authenticity of the data, and the unauthorised algorithm and the illegal reading and writing of the key will not produce the correct authentication code.
2 LEGIC non-contact IC card instruction flow
After receiving the instruction of the card reader, the non-contact IC card undergoes instruction decoding, performs data processing under the control of the finite state machine, and returns a corresponding processing result between the non-contact IC card and the card reader. The trading process is shown in Figure 6. .jpg)
The main program block diagram of the single-chip microcomputer system is shown in Figure 7. After completing the initialization, the loop of the test card and the scan key is entered. Waiting for the transfer card processing or the function key processing subroutine to execute the display field if there is a display interrupt request, the display field is executed. If there is a serial communication interrupt request, the shift refresh receives the loss report card number sent from the host or sends the consumption record data to the host. .jpg)
Figure 7 Non-contact card instruction flow chart
Based on the LEGIC system, the campus card system is developed. The networking mode is shown in Figure 8. .jpg)
Figure 8 Networking diagram of the LEGIC system
The POS machine of each system adopts RS485 connection. The POS machine uses the optical communication isolation between the asynchronous communication port of AT89C52 single chip and SN75176. The circuit schematic is shown in Figure 9.
In order to ensure the security of the system, the central database server is equipped with a UNIX operating system platform. The ORACLE large database system has a built-in card system dedicated encryption card. The ORACLE database is a unified campus card cardholder's personal basic information and e-wallet amount and merchant account information. The central database provides the data needed for each subsystem of the school. According to the size of the school, the size of the business flow and the management mode, higher-grade servers and data storage devices can be used to ensure data security and reliability. The stability center server can directly access the virtual private network provided by the campus network according to actual needs. Figure 10 shows the consumer subsystem interface. .jpg)
Figure 9, Schematic diagram of RS485 communication port .jpg)
Figure 10 consumer subsystem interface
This paper discusses the security issues, password authentication, networking principles, and operation modes of the LEGIC non-contact IC card system. This system has certain value for the promotion of all-in-one cards in colleges and universities. This system has been applied for two years in the teaching and consumption of our school. Proof of good results.
(Text/Tianjin University of Technology, School of Computer Technology and Automation: Wan Zhenkai)
September 07, 2019