Dual Interface Card

    Along with the information of world technical develop continuously,the economic exchanges between people becomes more frequent and complex,it encourages people to look for various communication medium,Smart card has always played an important part in our lives from early magnetic stripe card to the memory card,logic encryption card and CPU card,but in contact card popularization,there are various problems exist in the course of contact card popularization：
■  abrasion between the contact card and the card reader will decrease of service life；
■  bad connection between conduction medium, it can lead to data error；
■  inefficiency caused by insertion process in a large group of people.
     People combined radio-frequency technology to smart card technology to solve these problems so as to produce the contactless card，it has no surface contact,so,communicate to I/ O module by electromagnetic coupling because the chip and antenna was be packaged inside the card.

In comparison with contact card, contactless card has folow advantages：
■  no surface contact，so it avoid to be weared and easy to print；
■  operation convenient and rapid,card reader can operate card in any direction within a certain distance.
    Contactless card,which is currently the most popular smart card be divided into logic encryption card and CPU card.CPU card is more secure ,efficient and flexible than logic encryption card,but logic encryption card which conforms to the 14443 TYPE A standard account for the vast majority of market share,CPU card conforms to the 14443 TYPE B standard.

Despite its merits, contactless card also brings some problems to solve：
■  electromagnetic or radio frequency interference situation limits its application；
■  low power consumption；
■  still use contact card in many industries because of many associated infrastructure.
    From the above analysis have their own characteristics.With this situation, the dual interface card have emerged,it essentially provides two interface connection ways on a smart card（contact card&contactless card）.It is also a multi-function card because combine with the advantages of contact card and contactless card,it looks like contact card but insides as contactless card.

Technology 
    There are three main types of the dual interface card structure：
1.put contact chip and  logic encryption chip together in a card,this two system control seperately by two chips,and also have two EEPROM memory.
2.consist of one chip and antenna,it not only has contactless logic encryption card  function, but contact CPU card function,this two system use one EEPROM memory.
3.consist of one chip and antenna,it share the same EEPROM memory,microprocessor,ROM and RAM control two systems
    Actually ,the last form  is true meaning of the dual interface cards and inevitable trend of the development in the future.

Structure
    System mainly includes CPU,ROM,RAM,EEPROM,security control module,encryption coprocessors(DES、3DES、RSA).The technological difficulty as follow：
1.security of system：dual interface card safety system was composed of three different level models,firstly was physical security of the chip,such as anti software tracking；secondly was secure technology of card manufacturing；thirdly was communication security of card such as encryption algorithm.They work together constitute a card security system.There was no clear boundary among the three in actual use,For example,the dual interface card with DES(3DES),RSA coprocessor,with the help of software and hardware to ensure security system.Now,PKI(Public Key Infrastructure) can make two people communicate with each other everywhere in the world through Internet.ans also insure authentication and confidentiality.The relationship between smart card and PKI is that the key storage and the digital certificate storage,this card contain digital certificate and private key ，so it can achieve identification and information encryption transmission.Those emerging technologies provide more choices in the secure transaction of smart card.
2.COS develop smart card was determined by two factors：chip design and COS performance,not excepting the dual interface card.COS performance impacts directly on the performance of card,particularly need to process actions under the two models and ability to freely switch,it means higher requirements are set for the COS development.
3.engery in contactless mode：CPU usually were not battery powered,so the power of chip was supplied by electromagnetic coupling.The antenna of card need special design to supply stable current in data processing.
4. anti-collision algorithm：data may be misread when used  more than one contactless card entered the active area of the card reader at the same time.So only one card was allowed to be read,other cards were dormant,and be actived one by one after end of processing,each card would not impact on each other.
5.ultralow-power：considering  limited space in card, special CMOS ultralow-power and dormant technology must be used,adopt 14443 Type B standards also could increase supply rate of the energy.
6.packaging process：there were many parts need to be packaged into the dual interface card,such as antenna and chip,it must use unique packageing technology to ensure the size,thickness,flexibility and reliability of card.

Application
    It is connected with the virtue of contact card and contactless card,so it has characteristic:extensive applicability,"a multi-purpose card" and almost be used in any occasion. The most important was that no need to replace the software and hardware for original user who has already used contact card and contactless card,only certain modifications of software could upgraded to dual interface card.
Typical Application As:
■ public transport system,such as bus,subway,taxi and ferry magement or upgrade the old contactless card also implements the interface between bank balance system；
■ urban public charges,such as telephone,electricity meter,gas meter and water meter realize remote payment or bank statement；
■ public toll system,such as motorway,pier,parking meters and entertainment traditional IC card system can be upgraded to the Non-parking Charging System；
■ finance,such as bank,post,telecom,stock markets,shopping mall；
■ exit-inlet management system,such as duty management,attendance management,access control;　
■ encryption and authentication,such as SIM card,e-commerce transactions card,electronic transfer card,encrypt card and shield card. 

Market Prospect
    There are pros and cons to both the contactless card and the contact card in different situations.the feature of contact card was high safety and slow speed,but the contactless card showed an opposite condition.Achieving "a multi-purpose card"was one of smart card goals,combining with the advantages of two cards, dual interface card will certainly become a new hot issue of global development in the smart card market.
    Now, with the implementation of some smart card extension policies,dual interface card as more competitive in the domestic market.Government points out that give priority to the development of information industry, in the economic and social field extensive application of information technology. And this means the development prospect of dual interface card is unlimited.