Information processing system, information processing method, and information processing apparatus

1. An information processing system comprising:

a first apparatus that divides a user key of a share-source user through a secret distribution process to generate a plurality of distribution keys;

a second apparatus that sends a processing request to execute a predetermined process by using one of a plurality of the distribution keys generated by the first apparatus; and

a third apparatus that makes a determination based on one of a plurality of the distribution keys generated by the first apparatus and the processing request received from the second apparatus, wherein

the first apparatus provides the respective distribution keys different from each other among a plurality of the generated distribution keys to the second apparatus used by a share-target user and the third apparatus,

the second apparatus sends a hash value to the third apparatus, the hash value being calculated through homomorphic hash calculation based on the received distribution key and input data, and

the third apparatus compares a hash value calculated through homomorphic hash calculation based on the hash value received from the second apparatus and the distribution key received from the first apparatus with a hash value calculated through homomorphic hash calculation based on the user key to determine whether or not to execute the predetermined process.

2. The information processing system according to claim 1 , wherein the third apparatus executes the predetermined process in a case where the hash value calculated through the homomorphic hash calculation based on the hash value received from the second apparatus and the distribution key received from the first apparatus matches the hash value calculated through the homomorphic hash calculation based on the user key.

3. The information processing system according to claim 1 , wherein the predetermined process includes presenting a search result of encrypted data stored in the third apparatus,

the second apparatus sends a hash value to the third apparatus, the hash value being calculated through homomorphic hash calculation based on the received distribution key and a search word,

the third apparatus sends a search result corresponding to the search word to the second apparatus in a case where an encrypted index corresponding to the encrypted data includes the hash value received from the second apparatus, and

the encrypted index includes a hash value calculated through homomorphic hash calculation based on a keyword list extracted from the encrypted data and the user key of the share-source user.

4. The information processing system according to claim 3 , wherein the search result includes at least any of the encrypted data including the search word or a list of the encrypted data including the search word.

5. The information processing system according to claim 3 , wherein the third apparatus sends re-encrypted data to the second apparatus as the search result, the re-encrypted data being obtained by re-encrypting the encrypted data by using proxy encryption.

6. The information processing system according to claim 5 , wherein

the first apparatus receives a public key of the share-target user from the second apparatus that provides the distribution key, and sends a re-encryption key to the third apparatus, the re-encryption key being generated by using the public key and a secret key of the share-source user,

the third apparatus sends the re-encrypted data to the second apparatus, the re-encrypted data being obtained by re-encrypting the encrypted data by using the received re-encryption key, and

the second apparatus decrypts the received re-encrypted data by using a secret key of the share-target user.

7. The information processing system according to claim 3 , wherein the first apparatus sends the encrypted data and the encrypted index to the third apparatus, the encrypted index being generated through homomorphic hash calculation based on the keyword list extracted from the encrypted data and the user key of the share-source user.

8. The information processing system according to claim 7 , wherein the first apparatus generates the encrypted index obtained by encoding a hash value into a form of AMQ (Approximate Membership Query), the hash value being calculated through the homomorphic hash calculation based on the keyword list and the user key of the share-source user.

9. The information processing system according to claim 8 , wherein the form of AMQ includes at least a Bloom filter.

10. The information processing system according to claim 1 , wherein the third apparatus deletes the distribution key received from the first apparatus on a basis of a deletion request from the first apparatus.

11. The information processing system according to claim 1 , wherein the first apparatus generates the distribution keys through the secret distribution process, the distribution keys being greater in number than the share-target users by one.

12. The information processing system according to claim 11 , wherein

the first apparatus provides the respective distribution keys different from each other to a plurality of the second apparatuses and the third apparatus, and

the third apparatus compares hash values calculated sequentially by all a plurality of second apparatuses through homomorphic hash calculation using the distribution keys with the hash value calculated through the homomorphic hash calculation based on the user key.

13. The information processing system according to claim 12 , wherein

a plurality of the second apparatuses includes a starting-point terminal serving as a starting point of the processing request, and a passing terminal through which the processing request passes,

the starting-point terminal sends the hash value to the passing terminal, the hash value being calculated through the homomorphic hash calculation based on the received distribution key and the input data, and

the passing terminal sends a hash value calculated through homomorphic hash calculation based on the received distribution key and a hash value received from the starting-point terminal or from one or more other passing terminals to at least one other passing terminal that has not performed the homomorphic hash calculation or to the third apparatus.

14. The information processing system according to claim 13 , wherein, in a case where the at least one other passing terminal that has not performed the homomorphic hash calculation exists, the passing terminal sends the hash value to the at least one other passing terminal, and in a case where there are no other passing terminals that have not performed the homomorphic hash calculation, the passing terminal sends the calculated hash value to the third apparatus.

15. The information processing system according to claim 1 , wherein

the predetermined process includes a settlement process, and

the third apparatus executes the settlement process in a case where the hash value received from the second apparatus matches a hash value calculated through homomorphic hash calculation based on the user key and the input data.

16. The information processing system according to claim 1 , wherein

the predetermined process includes a document disclosing process, and

the third apparatus executes the document disclosing process in a case where the hash value received from the second apparatus matches a hash value calculated through homomorphic hash calculation based on the user key and the input data.

17. The information processing system according to claim 1 , wherein the third apparatus controls an interface for inputting the input data and displaying a result of the processing request.

18. An information processing method comprising:

dividing, by a first apparatus, a user key of a share-source user through a secret distribution process to generate a plurality of distribution keys;

sending, by a second apparatus, a processing request to execute a predetermined process by using one of a plurality of the distribution keys generated by the first apparatus; and

making, by a third apparatus, a determination based on one of a plurality of the distribution keys generated by the first apparatus and the processing request received from the second apparatus, the information processing method further including

providing, by the first apparatus, the respective distribution keys different from each other among a plurality of the generated distribution keys to the second apparatus used by a share-target user and the third apparatus,

sending, by the second apparatus, a hash value to the third apparatus, the hash value being calculated through homomorphic hash calculation based on the received distribution key and input data, and

comparing, by the third apparatus, a hash value calculated through homomorphic hash calculation based on the hash value received from the second apparatus and the distribution key received from the first apparatus with a hash value calculated through homomorphic hash calculation based on the user key to determine whether or not to execute the predetermined process.

19. An information processing apparatus comprising:

a secret distribution processing unit configured to divide a user key of a share-source user through a secret distribution process to generate a plurality of distribution keys; and

a communicating unit configured to

send one or more first distribution keys of the plurality of the distribution keys to a terminal used by a share-target user, and

send one or more second distribution keys of the plurality of the distribution keys to a server configured to store encrypted data,

wherein the one or more first distribution keys and the one or more second distribution keys are different from each other,

wherein the server is configured to compare a hash value calculated through homomorphic hash calculation based on the one or more first distribution keys with a hash value calculated through homomorphic hash calculation based on the one or more second distribution keys to determine whether or not to execute a process, and

wherein the secret distribution processing unit and the communicating unit are each implemented via at least one processor.

20. The information processing apparatus according to claim 19 , further comprising

an encrypting unit configured to generate the encrypted data by using the user key,

wherein the communicating unit is further configured to send the encrypted data to the server,

wherein the share-target user includes a user who is permitted by the share-source user to search the encrypted data, and

wherein the encrypting unit is implemented via at least one processor.