Abstract: A data processing apparatus capable of updating and writing a plurality of distributed information items generated based on to-be-held secret information with respect to a data storage device in which access is not limited includes a secret distribution processing portion which generates a plurality of distributed information items updated this time according to secret information to be held this time based on a threshold value secret distribution method, and a distributed information management portion which selects recording positions of distributed information items updated this time to leave behind distributed information items of a number less than a threshold value among a plurality of distributed information items updated last time with respect to a plurality of distributed information items updated and stored in the data storage device and writes distributed information items updated this time to the data storage device based on the selected recording positions.