To prevent tracking by a malicious subject while entrusting restoration processing to a restoring device.
A distributed information management device 2 stores each of the n-number of distributed information generated from secret information to be kept secret using a (k, n) threshold secret sharing scheme. An information utilizing device 1 generates and stores the n-number of random numbers, and makes an information restoration request including a distributed information identifier for uniquely identifying the requested distributed information, and the respective random numbers. A distributed information management device 2 conceals the distributed information by the random numbers and transmits it to a restoring device 3. Upon receiving the k-number of concealed distributed information, the restoring device 3 performs restoration processing of the (k, n) threshold secret sharing scheme to restore the concealed secret information. The information utilizing device obtains the secret information by decoding the restored concealed secret information using the random numbers.
YAMANAKA SHINJI
TAKAHASHI TOSHINARI
