1. Field of the Invention
The present invention relates to an IC card and an IC card case devised to prevent illegal use and battery charger for supplying power to the IC card case.
2. Description of the Related Art
Integrated circuit (IC) cards have come to be used in various fields as employee ID cards, club member ID cards, insurance ID cards, etc., in addition to business transaction cards, such as credit cards and debit cards. Since IC cards are equipped with a CPU, ROM, RAM, EEPROM, etc., which are not incorporated in conventional magnetic cards, they can have various functions and are hard to forge, which significantly enhances their security. Therefore, IC cards are often used to store personal information (see, for example, Jpn. Pat. Appln. KOKAI Publication No. 2001-312711).
Attention has recently been paid to power analysis attacks against IC cards. In these attacks, the key used in an encryption scheme, such as DES and RSA, which is often utilized when IC cards are identified by a card reader, is found by analyzing the power consumed while the decryption algorithm is being executed. Such methods as the above for attacking IC cards without opening the cards have greatly advanced.
As described above, IC cards are hard to forge and hence have come to be widely used to store personal information, while IC card attacking methods have greatly advanced. Therefore, if an IC card is lost and acquired by a third party, it can be used illegally, resulting in serious damage.
As a countermeasure to cope with, for example, an IC card being lost and acquired by a third party, the amount of money that can be transacted in a single month is limited, or the number of occasions the card can be used is limited. However, this is not a fundamental solution for preventing illegal use when an IC card is lost. As another countermeasure, some IC cards have a built-in timer for limiting the period of the validity of the card. In this case, however, a power supply must be incorporated in the card to allow the timer to operate continuously, which is a serious problem for IC cards, as their specifications are limited.