This is to provide an image processing apparatus and others capable of ensuring security by shortening the connecting time of an external recording medium when a plurality of jobs including target data pieces encrypted with shared keys and the shared keys encrypted with a user's public key are executed. A job including a target data piece encrypted with a shared key and the shared key encrypted with a user's public key are received and stored in a job storage. To execute the plurality of jobs stored therein, the encrypted shared keys included in the respective jobs are decrypted with a secret key by the external recording medium. After completely obtaining all the plurality of decrypted shared keys, the target data pieces are decrypted with their matching decrypted shared keys, and then the jobs are executed.