SECRET SHARING SYSTEM, DATA DISTRIBUTION DEVICE, DISTRIBUTED DATA CONVERSION DEVICE, SECRET SHARING METHOD, AND PROGRAM

摘要

A secret sharing system converts a computational secret sharing distribution value to a homomorphic secret sharing distribution value. In a data distribution device, a key selection unit selects K'-1 number of keys (sj). A pseudorandom number generation unit generates a pseudorandom number (rj) from the keys (sj). An encryption unit generates an encrypted text (c) from a set of information (a) by using the pseudorandom number (rj). A key distribution unit distributes the keys (sj) into N number of distribution values (fsj(n)) by means of a given secret sharing method (S1). An encrypted text distribution unit distributes the encrypted text (c) into N number of distribution values (fc(n)) by means of a given distribution method (S0). In a distributed data conversion device, when K number of distribution values (fsj(i)) are inputted, a decompression unit extracts distribution values (fsj(i)) by means of the secret sharing method (S1) and generates a decompression value (Uj), and when K number of distribution values (fc(i)) are inputted, the decompression unit extracts distribution values (fc(i)) by means of the given distribution method (S0) and generates a decompression value (Uj(j=K')). A redistribution unit distributes decompression value (Uj) into N number of distribution values (fUj(n)) by means of a homomorphic secret sharing method (S2). A conversion unit generates a distribution value (ga(i)) of the information (a) from K' number of distribution values (fUj).