| 摘要 |
The Information providing system includes a key management center, information transmitter and information receiver. The key management center assigns, to the receivers, confidential information and public information for decrypting the encrypted information transmitted by the information transmitter. The key management center determines the set of the receivers for which decryption of the encrypted information is not permitted, generates key information that can be decrypted only by the receivers other than the set, and transmits the key information with the information encryption key for encrypting the transmission information to the information receivers. The information transmitter encrypts the transmission information with the information encryption key of the transmission information to produce the encrypted information, and transmits it to the information receivers with the key information.
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