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

摘要

A secret sharing system transforms shares in ramp secret sharing to shares in homomorphic secret sharing. On a data distribution apparatus, a division part divides information a into N shares f a (n) using an arbitrary ramp secret sharing scheme S1. On each of distributed data transform apparatuses, a random number selecting part generates a random number vector r i whose elements are L random numbers r i1 . A first random number division part divides the random number vector into N shares f ri (n) using a ramp secret sharing scheme S1. A second random number division part divides each of the L random numbers r i1 into N shares g ri,1 (n) using an arbitrary secret sharing scheme S2. A disturbance part generates a share U i by using a share f a (i) and shares f r» (i). A reconstruction part reconstructs L pieces of disturbance information c 1 from shares U » by using the ramp secret sharing scheme S1. A redivision part divides each piece of disturbance information c 1 into N using the secret sharing scheme S2 to generate shares g c1 (n). A transform part generates shares g a1 ( 1 ) of the information a by using a share g c1 (i) and the shares g r»,1 (i).