Patent ID: 7360091
Filing Date: 2008-04-15
Classification: G06Q

Abstract:
1. A smart card, comprising: a communication unit to communicate with the outside; an information accumulating unit to accumulate data and a program; and an arithmetic processing unit to perform information processing, wherein said information accumulating unit stores value data, a transfer key that encrypts the value data, a transfer key identifier that verifies whether the transfer key is newer or older in accordance with a value of the transfer key identifier, an update key that encrypts the transfer key, and an upper limit of the transfer key identifier that represents an upper limit of the transfer key identifier that can be stored by the smart card, wherein said arithmetic processing unit updates the transfer key identifier and the transfer key by performing encryption using the update key on the basis of common-key cryptography, wherein said arithmetic processing unit updates the value data by performing encryption using the transfer key on the basis of the common-key cryptography, wherein if command data that requests transmission of card information is received, said arithmetic processing unit transmits said transfer key identifier to the outside as response data, wherein if command data that requests update permission of said transfer key is received, said arithmetic processing unit generates a first random number and transmitting said first random number to the outside as response data, wherein if command data which requests to obtain said transfer key, and which stores a second random number, is received, said arithmetic processing unit transmits first encrypted data, into which the second random number, said transfer key identifier, and said transfer key are encrypted by use of said update key on the basis of common-key cryptography, to the outside as response data, and wherein if command data which requests update of said transfer key, and which stores second encrypted data, is received, said arithmetic processing unit decrypts said second encrypted data by use of said update key on the basis of common-key cryptography to extract first data, second data, and third data, and if said first data is equivalent to said first random number, and if a value of said second data is between a value of said upper limit of transfer key identifier and a value of said transfer key identifier, changes a value of said transfer key identifier to a value of said second data, and chances a value of said transfer key to a value of said third data.