To reduce the amounts of calculation and communication.

Sets mi (I-0,..., k-1) of information desired to be transmitted by transmission equipment 100 are enciphered (110) and an enciphered message ci is sent to reception equipment 200. The equipment 200 selects (j) pieces of cij (j-0,..., f-1) (1≤f<k) desired to be received out of the received ci and sends them to the equipment 100 as question information Xj while scrambling them with a generated random number rj. At the equipment 100, the question information Xj is decoded and sent to the equipment 200 as answer information Yj (120). At the equipment 200, the random number rj is removed from the answer information (Yj) and selected information mij is provided (240).