| 摘要 |
An information providing system includes first and second apparatuses. The first apparatus includes a memory storing a shared random number Ri and shared information, a providing unit providing the second apparatus with encrypted information e(Ki, Fi) obtained by encrypting information Fi with an encryption key and an encrypted key Yi obtained by encrypting a decryption key Ki with the random number Ri, and an updating unit updating Ri to Ri+1 based on the shared information. The second apparatus includes a memory storing the random number Ri and the shared information, an acquiring unit acquiring the encrypted information e(Ki, Fi) and the encrypted key Yi, a key decrypting unit decrypting the encrypted key Yi with the random number Ri to calculate the decryption key Ki and updating Ri to Ri+1 based on the shared information, and an information decrypting unit decrypting the encrypted information e(Ki, Fi) with the decryption key Ki. |
| 主权项 |
1. An information providing system comprising a first apparatus and a second apparatus, the first apparatus including
(A) a first memory that stores an i-th (i represents an integer of 1 or greater) shared random number Ri and shared information for updating the shared random number Ri to an (i+1)-th shared random number Ri+1, which are shared by the first apparatus and the second apparatus, (B) a providing unit that provides encrypted information e(Ki, Fi) and an encrypted key Yi to the second apparatus, the encrypted information e(Ki, Fi) obtained by encrypting provision target information Fi, which is to be provided in the i-th place to the second apparatus from the first apparatus, with an encryption key corresponding to the provision target information Fi, and the encrypted key Yi obtained by encrypting a decryption key Ki corresponding to the encryption key with the shared random number Ri, and (C) a shared random number updating unit that updates the shared random number Ri stored in the first memory to the (i+1)-th shared random number Ri+1 in accordance with the shared information after the encrypted key Yi is obtained by encrypting the decryption key Ki with the shared random number Ri, to thereby generate the (i+1)-th shared random number Ri+1, and the second apparatus including (a) a second memory that stores the shared random number Ri and the shared information, (b) an encrypted information acquiring unit that acquires the encrypted information e(Ki, Fi) and the encrypted key Yi corresponding to the i-th provision target information Fi, which are provided from the first apparatus, (c) an encrypted key decrypting unit that decrypts the encrypted key Yi acquired by the encrypted information acquiring unit with the shared random number Ri to thereby calculate the decryption key Ki, and updates the shared random number Ri stored in the second memory to the (i+1)-th shared random number Ri+1 in accordance with the shared information after the use of the shared random number Ri to calculate the decryption key Ki, to thereby generate the (i+1)-th shared random number Ri+1, and (d) an information decrypting unit that decrypts the encrypted information e(Ki, Fi) into the provision target information Fi with the calculated decryption key Ki. |
