Patent ID: 8074266

Claim:
A memory card adapted to receive data from a writing apparatus, to store the received, and to send the stored data to a reading apparatus, the memory card comprising: a card certificate storing unit storing a certificate including a first public key; a certificate sending unit sending the certificate stored by the card certificate storing unit to the writing apparatus; a confidential data receiving unit receiving confidential data from the writing apparatus, the confidential data being a combination of a common key encrypted by the writing apparatus using the first public key included in the certificate sent from the certificate sending unit, and signature data, which includes data to be read by the reading apparatus, encrypted by the writing apparatus using the common key; a public storing unit, which is readable and/or writable from outside without authentication, storing the confidential data received by the confidential data receiving unit; a card private key storing unit storing a first private key which forms a pair with the first public key; a common key obtaining unit obtaining the encrypted common key from the confidential data stored by the public storing unit; a signature data obtaining unit obtaining the encrypted signature data from the confidential data stored by the public storing unit; a common key decrypting unit decrypting the encrypted common key obtained by the common key obtaining unit using the first private key stored by the card private key storing unit; a signature data decrypting unit decrypting the encrypted signature data obtained by the signature data obtaining unit using the common key decrypted by the common key decrypting unit; an authentication data receiving unit receiving authentication data sent from the reading apparatus; an authentication data storing unit storing proper authentication data that only an owner of the memory card knows; an authenticating unit performing the authentication by comparing the authentication data received by the authentication data receiving unit with the proper authentication data stored by the authentication data storing unit; a data obtaining unit obtaining the data to be read by the reading apparatus from the signature data decrypted by the signature data decrypting unit; a private storing unit, which is readable and/or writable from outside only when authentication performed by the authentication unit succeeds, storing the data obtained by the data obtaining unit; and a card data sending unit sending the data stored by the private storing unit to the reading apparatus when the authentication performed by the authenticating unit succeeds.