0 Preface
With the continuous development of China's economy and the continuous deepening of the national tax reform, the requirements for tax collection management and tax inspection work are more stringent, and the tax workload is also growing. How to use computer management instead of manual management in tax work to realize electronic tax collection has become a new topic for tax authorities. "SZX-1 intelligent IC card tax collection management system" came into being under this background. The SZX-1 intelligent IC card tax collection management system uses the IC card conforming to the ISO-7816 standard as the reporting information carrier, and stores the tax return and financial statement data in the IC card, which solves the manual processing of the declaration data in the tax collection work. The cumbersome labor has greatly shortened the reporting time and improved the work efficiency.
The introduction of SZX-1 intelligent IC card tax collection management system not only realizes the convenience and speed of tax collection, but also improves the standardization, accuracy and scientificity of tax management work, thus ensuring the smooth progress of tax collection.
1 system composition
This system consists of a PC and an IC card reader, as shown in Figure 1. The IC card reader is mainly composed of AT89C52 single chip microcomputer, MAX232 serial communication level conversion chip, IC card card holder, power supply, single chip reset circuit, single chip clock circuit, etc., as shown in Figure 2.
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2 IC card technology
With the development of very large scale integrated circuits, an integrated circuit IC is embedded in a card similar to a credit card, which is called an IC card. If the microcontroller is also embedded in the card, it is called a smart card. IC cards can be roughly classified into the following four types according to their structure and application characteristics:
(1) Memory card
The memory card is a magnetic strip that replaces the magnetic card with a semiconductor memory and functions like a magnetic card. The integrated circuit in the memory card may be a ROM, a PROM, an EPROM, an EEPROM or the like. Due to the development and widespread application of electrically rewritable EEPROMs, memory cards containing EEPROM have become the mainstream of memory card development. The memory card can be combined with a simple password, so its reliability and confidentiality are higher than the magnetic card.
(2) Payment card
A pay card is essentially a type of memory card. This type of IC card is prepaid, and the corresponding money is deducted in the future. It can only be reduced. After the amount in the card is deducted, the card can be re-purchased (ie, the amount is rewritten).
(3) Smart card
The smart card not only embeds the memory but also embeds the CPU, so the smart card is often called the CPU card. In addition to the large-capacity storage function, the smart card also has an intelligent function that is different from the general IC card, such as security and identification. Smart cards are the development direction of IC cards, and are currently mainly used in banking, finance, POS systems and information management access systems.
(4) Passcard The passcard is also a type of smart card. It embeds a hardware cryptographic calculation unit on the basis of the smart card to meet the requirements of the RSA cryptographic algorithm. The PIN card is a high performance smart card that has been developed in recent years.
Compared with magnetic cards, IC cards have the following advantages:
· Large storage capacity (up to 10K bytes), greatly exceeding the storage capacity of the magnetic card;
·Safe and confidential performance is good, this is the magnetic card can not be compared with it;
· High read/write reliability (much higher than magnetic cards);
· One card for multiple use, that is, "one card";
· The smart IC card is a stand-alone computer that can be used without networking, and is more practical for areas where communication equipment is backward.
In order to facilitate the development and application of IC cards, the ISO has established the following standards:
· 7816-1: physical characteristics of the IC card, such as hardness, toughness, bending resistance, etc.;
· 7816-2: size of the IC card, location of the contact point;
· 7816-3: The electrical signal of the IC card, such as the definition of the electrical signal, voltage, current, operating frequency, transmission protocol at startup;
· 7816-4: Inter-industry orders for IC cards for international exchange;
· 7816-5: Numbering and registration process for IC card application identification;
· 7816-6: IC cards are used for data elements between industries.
In the selection of the type of IC card, the system selects the CPU card of Atmel Company, the logic encryption card of Siemens company and the memory card. The CPU card is used for the operation of the DKS encryption algorithm to generate key data such as keys; the logical encryption card is used to store important data; the memory card is used to store general data.
3 DES encryption algorithm
Cryptography is a general term for designing passwords and deciphering passwords. The data to be encrypted is called plaintext, and the plaintext is converted into ciphertext by the action of some encryption algorithm, and the parameter used in the encryption algorithm is called an encryption key. The ciphertext is formed into a plaintext output by the decryption algorithm, and the decryption algorithm also has a key, which may be the same as or different from the encryption key. One of the basic principles of cryptography is that the encryption algorithm is public. Since the encryption algorithm is public, the real secret is the key. The key must be kept secret, it is usually a string, and can be changed frequently as needed.
Traditional encryption methods can be divided into two categories: replacement passwords and transposition passwords. In the alternative password, a set of ciphertext letters is used instead of a set of plaintext letters to hide the plaintext, but the position of the plaintext letters is kept the same. In transposition ciphers (transformation is sometimes referred to as permutation), it does not transform the plaintext letters, but rearranges the order of the plaintext letters.
Modern cryptography also uses the idea of ​​replacing passwords and transposing passwords, but it is different from traditional cryptography. The traditional cryptography encryption algorithm is relatively simple, mainly by lengthening the length of the key to improve the degree of confidentiality, while modern cryptography is just the opposite, it uses an extremely complex encryption algorithm, even if the decipher can encrypt any number of selected plaintext, he It is also impossible to find a way to decipher the ciphertext.
DES was developed by IBM and was announced by the US government as an open national data encryption standard in January 1977. Once established, it was immediately adopted by a large number of manufacturers for their security products. DKS is a block cipher that receives a 64-bit (BIT) block of data and converts it into ciphertext of the same length. The key is 64 bits (BIT), where 8 bits (BIT) are parity bits, so the actual number of keys is 56 bits (BIT). The DES encryption algorithm can be briefly illustrated in Figure 3. The plaintext of 64-bit (BIT) is first scrambled by an initial arrangement, and then 16 times of product transformation, in order to make the plaintext as chaotic as possible, and finally output 64 bits after an arrangement transformation opposite to the initial alignment. BIT) ciphertext. The decryption key of DES is the same as the encryption key, and the decryption process is exactly the opposite of the encryption process.
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Figure 3 DES algorithm process
4 software design
SZX-1 intelligent IC card tax collection management system software consists of PC software, IC card reader software and PC and IC card reader communication software. The PC software is written in VB6.0, and the IC card reader software is written in C51.
4.1 Serial Communication Software Design
When designing the communication program between PC and MCU, the data transmission protocol should be clarified first, such as: frame format of data transmission, data verification method, working mode of PC and MCU in asynchronous communication, and so on. The various conventions in this system are:
(1) Baud rate: 9600
(2) Data format One frame 10 bits: start bit 1 bit, data bit 8 bit, stop bit 1 bit (3) Data check method: feedback one confirmation method (4) Asynchronous communication work mode: PC uses MSComm serial port Control; MCU uses the query mode to send and receive data, and its serial port works in mode l.
The MSComm serial port control is an ActiveX control provided by Microsoft Corporation. The purpose is to simplify the serial communication programming of the user under Windows. The MSComm control provides both simple serial port communication and the creation of full-featured, event-driven, advanced communication tools. The serial communication control using the MSComm control usually has the following steps:
(1) join the communication component (ie join the MSComm object);
(2) Set the communication port number (that is, set the CommPort attribute);
(3) Set the communication protocol (that is, set the HandShaking attribute. This protocol is an internal hardware handshake protocol for controlling the flow rate);
(4) Set communication baud rate, number of data bits, stop digits, parity and other parameters (ie set the Settings property);
(5) Open the communication port (ie, set the PortOpen property to True);
(6) receiving or sending a string (ie using the Input or Output attributes);
(7) Close the communication port (ie, set the PortOpen property to False).
4.2 System Software Features
The main function interface of this system running on PC is as follows:
(1) After the software runs, the screen displays:
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(2) Use the mouse to select “Continue†or press “Enterâ€. The screen displays the basic information of the enterprise. The taxpayer will fill in the change in the current month:
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(3) There are four function buttons in the interface of the enterprise basic situation table, in which “write (W)†is used to modify the data in the situation table, press the “write (W)†function button, and the IC card The latest input (or modified) data is stored. “Continue (H)†is used to enter the main menu state. The main menu provides the contents of the tax, fund, fee, tax return, corporate financial statements, tax information, etc. that the taxpayer should declare. After pressing the "Continue (H)" function button, the screen displays:
(4) Fill in the statement. In the main menu state, the taxpayer uses the mouse or the “↑†and “↓†cursor keys to select the type of the declaration form. After selecting it, press the “Enter†key to confirm, and the corresponding declaration form will be displayed on the screen for the taxpayer to fill out. If you choose to select “1. Urban Construction, Business, Fund Tax Returnâ€, the screen displays: Select one of the three options from 1 to 3 according to the tax content, the corresponding tax return will be displayed on the screen, and then according to the report content. Fill in and press the “Write†button after confirming that the information is correct. The data in the tax return form is stored in the IC card, and the tax declaration work is completed.
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In addition, there is a “Tax Information Delivery†item in the main menu. Its function is to enable taxpayers to keep abreast of relevant tax policy information in order to maintain the relationship between the tax authorities and taxpayers after canceling the tax administrator system. The dynamic use of the IC card as a carrier of tax information transmission, when the taxpayer's monthly tax return is over, the tax authorities will write the relevant tax policy information into the IC card, and the taxpayer will pass the SZX-1 intelligent IC card tax collection management system. The software can read, save, and print tax information.
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5 Conclusion
The SZX-1 intelligent IC card tax collection management system has been put into use in a local taxation department with good results and achieved the intended purpose. With the continuous deepening of tax reform, with the continuous development of computer technology and IC card technology, the electronicization of tax collection management and tax inspection work will be more perfect.
(Text / Suzhou Vocational University Xia Liying Li Lina)
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