A data processing apparatus includes an auxiliary storage device having target verification data stored therein, a program memory having a validity verification program stored therein, a first RAM (Random Access Memory), a second RAM, and an execution unit configured to execute a validity verification process in accordance with the validity verification program stored in the program memory. The execution unit is configured to copy the target verification data from the auxiliary storage device into the first RAM, execute the validity verification process on the copied target verification data in the first RAM, and use the second RAM as a work area in a case of executing the validity verification process.