| 摘要 |
A shared information creating device capable of detecting false alteration of shared information with high probability even if a traitor has shares the number of which is above a threshold and creating shared information whose data size is smaller than that of secret information. A recovering device, a recovery result verifying device, and a secret information sharing system, program, and method are also provided. The shared information creating device generates a polynomial F in which secret information s is embedded, outputs a shared secret information, generates a polynomial G in which the output of when a fixed value t is substituted in the polynomial F is embedded as secret information, and creates shared secret information. A recovering device receives k sets of shared secret information to generate a polynomial F′, and receives k sets of shared shared secret information to generate a polynomial G′. When the value embedded as secret information in the polynomial G′is equal to the output of when the fixed value t is substituted in the polynomial F′, the embedded value is outputted. When they are not equal, information indicating falsification detection is outputted.
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