Secret sharing system, data sharing device, distributed data conversion device, secret sharing method, and program

摘要

The secret sharing system converts the complexity value of the secret sharing type into a secret sharing value having homomorphism. In the data distribution apparatus, the key selection unit selects K′−1 keys sj. The pseudo random number generator generates a pseudo random number rj from the key sj. The encryption unit generates a ciphertext c from the information a using the pseudo random number rj. The key distribution unit distributes the key sj into N distributed values fsj (n) using an arbitrary secret sharing scheme S1. The ciphertext distributing unit distributes the ciphertext c into N distributed values fc (n) by an arbitrary distribution method S0. In the distributed data conversion apparatus, when K restoration values fsj (i) are input, the restoration unit restores the dispersion value fsj (i) by the secret sharing scheme S1, generates the restoration value Uj, and When the dispersion value fc (i) is input, the restoration value Uj (j = K ′) is generated by restoring the dispersion value fc (i) by the dispersion method S0. The redistribution unit distributes the restored value Uj into N distributed values fUj (n) by the secret sharing scheme S2 having homomorphism. The conversion unit generates the variance value ga (i) of the information a from the K ′ variance values fUj.