Reception terminal, key management apparatus, and key updating method for public key cryptosystem
First Claim
1. A method, for use in a data distribution system having a key management center, a distribution station, and a reception terminal, for updating a pair of a distribution public key and a distribution secret key which conform to a public key cryptosystem and are both unique to the reception terminal, the distribution public key being used to encrypt data to be distributed to the reception terminal, the distribution secret key being used to decrypt the distributed encrypted data, the method comprising:
- an update secret key acquiring step in which the reception terminal acquires an update secret key prior to a data distribution;
an update public key acquiring step in which the key management center acquires an update public key that makes a pair with the update secret key, prior to the data distribution;
a key generating step in which the key management center generates a new pair of a distribution public key and a distribution secret key for the reception terminal;
an encrypting step in which the key management center generates an encrypted secret key by encrypting the new distribution secret key using the update public key;
a transmission step in which the key management center transmits the encrypted secret key to the reception terminal;
a distribution public key updating step in which, after the transmission step, the key management center updates the distribution public key having been used so far by the distribution station in data distributions to the new distribution public key;
a reception step in which the reception terminal receives the encrypted secret key; and
a distribution secret key updating step in which the reception terminal restores the new distribution secret key as necessary by decrypting the encrypted secret key using the update secret key, and updates the distribution secret key having been used so far to the restored new distribution secret key.
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Abstract
A method for use in a distribution system having a key management center, a distribution station and a reception terminal. The method updates a pair of distribution keys unique to the reception terminal, the distribution public key being used to encrypt distribution data, and the distribution secret key to decrypt encrypted data. In the key updating method, the reception terminal acquires an update secret key prior to data distribution, the key management center acquires an update public key making a pair with update secret key, generates a new pair of distribution keys, encrypts new distribution secret key using update public key, transmits encrypted secret key to the reception terminal and updates to the new distribution public key. The reception terminal receives encrypted secret key and restores new distribution secret key by decrypting it using the update secret key and updates to the new distribution secret key.
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Citations
20 Claims
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1. A method, for use in a data distribution system having a key management center, a distribution station, and a reception terminal, for updating a pair of a distribution public key and a distribution secret key which conform to a public key cryptosystem and are both unique to the reception terminal, the distribution public key being used to encrypt data to be distributed to the reception terminal, the distribution secret key being used to decrypt the distributed encrypted data, the method comprising:
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an update secret key acquiring step in which the reception terminal acquires an update secret key prior to a data distribution;
an update public key acquiring step in which the key management center acquires an update public key that makes a pair with the update secret key, prior to the data distribution;
a key generating step in which the key management center generates a new pair of a distribution public key and a distribution secret key for the reception terminal;
an encrypting step in which the key management center generates an encrypted secret key by encrypting the new distribution secret key using the update public key;
a transmission step in which the key management center transmits the encrypted secret key to the reception terminal;
a distribution public key updating step in which, after the transmission step, the key management center updates the distribution public key having been used so far by the distribution station in data distributions to the new distribution public key;
a reception step in which the reception terminal receives the encrypted secret key; and
a distribution secret key updating step in which the reception terminal restores the new distribution secret key as necessary by decrypting the encrypted secret key using the update secret key, and updates the distribution secret key having been used so far to the restored new distribution secret key. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A reception terminal for restoring certain data by decrypting encrypted certain data distributed from a distribution station, using a distribution secret key unique to the reception terminal, the reception terminal comprising:
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an update secret key acquiring means for acquiring an update secret key prior to a data distribution;
a holding means for holding an encrypted secret key which is generated by encrypting the distribution secret key using an update public key that makes a pair with the update secret key;
a reception means for receiving the encrypted data from the distribution station;
a distribution secret key restoring means for restoring the distribution secret key unique to the reception terminal by decrypting the encrypted secret key held by the holding means, using the update secret key acquired by the update secret key acquiring means; and
a data restoring means for restoring the certain data by decrypting the encrypted certain data using the restored distribution secret key. - View Dependent Claims (9, 10, 11, 12, 14, 15, 16, 17, 18, 19, 20)
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13. A key management apparatus, comprising:
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an update public key acquiring means for acquiring, prior to a data distribution, an update public key that makes a pair with an update secret key held by a reception terminal;
a key generating means for generating a pair of a distribution public key and a distribution secret key for the reception terminal;
an encrypting means for generating an encrypted secret key by encrypting the distribution secret key using the update public key;
a transmission means for transmitting the encrypted secret key to the reception terminal;
a distribution public key updating means for, after the transmission step, updating the distribution public key having been used so far to the new distribution public key for use in data distribution.
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Specification