A data processing apparatus includes a memory storing a program and a processor configured to execute the program to implement a process of reading signed data including a predetermined number (n) of secret sharing data sets generated for each section of time series data and a signature value calculated for the each section of time series data based on a secret sharing protocol. The n secret sharing data sets include n units of data acquired from each section of time series data and parameter information for a polynomial of a predetermined degree calculated based on the acquired n units of data. The processor further implements processes of acquiring the predetermined degree, and editing the signed data by extracting a specific number of the secret sharing data sets from the n secret sharing data sets for the each section of time series data according to the acquired predetermined degree.