| 摘要 |
PROBLEM TO BE SOLVED: To provide a communication method capable of transmitting and receiving fast in a state where data in an IC card cannot be read from outside by interposing a buffer. SOLUTION: At the time of issuing an IC card 1, a personal key KTI obtained by ciphering a characteristic serial number ICj is stored in the IC card 1 and an opposed station 3. The IC card 1 combines a random number R2 from an external buffer 2 and a generated random number R1 before starting communication and ciphers it to be the key KTI to generate a temporary key KS. EKS(Data1) obtained by ciphering the data Data1 by the key KS is transmitted to the station 3 with the random numbers R1 and R2 through the buffer 2. The station 3 similarly combines the random numbers R1 and R2, ciphers it to be the key KT to generate the same temporary key KS and decodes EKS (Data1) with the key KS. Since the key KS is not transmitted and received, the data Data1 can be transmitted and received without leaking.
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