When a PC (a transmission device) transmits an externally taken-in audio file to an electronic dictionary (a receiving device), the PC encodes the audio file and stores the compressed audio file into its own memory temporarily. On the basis of the file management data created by a file management system when the compressed audio file was stored in the memory, the PC generates a file list for the audio files to be transferred. The file list is encrypted using an encryption key. Then, the encryption key, encrypted file list, and compressed audio file are transmitted to the electronic dictionary. The electronic dictionary stores the encrypted file list and compressed audio file into an SD card and decrypts the encrypted file list using the encryption key. When the decrypted file list corresponds to the compressed audio file, the process of expanding the compressed audio file into an audio file is permitted.