A data processing method for a wireless relay device (101A, 101B, 20), wherein the wireless relay device comprises a Wi-Fi module and is configured to operate a group of wireless portable devices (101A to 104A, 101B to 104B) by supporting Wi-Fi communication between members of the group of wireless portable devices via the Wi-Fi module, wherein the wireless relay device comprises a radio transmission and reception unit configured to relay wireless communication of the wireless relay device with another wireless relay device configured to operate another group of wireless portable devices by supporting Wi-Fi communication between members of the another group of wireless portable devices, and wherein the wireless relay device comprises a voice I/O unit configured to receive or output user voice signals, the method comprising: receiving, by the wireless relay device, a user voice signal; determining in a first determination step whether or not the user voice signal has been inputted by the wireless relay device itself; if it is determined in the first determination step that the user voice signal has been inputted by the wireless relay device itself, determining in a second determination step whether or not a recipient to receive the user voice signal corresponds to a member (101A to 104A, 101B to 104B) of a group (A, B) operated by the wireless relay device; if it is determined in the first determination step that the user voice signal has been inputted by the wireless relay device itself and if it is determined in the second determination step that the recipient to receive the user voice signal corresponds to a member of a group operated by the wireless relay device, encrypting the user voice signal, and outputting the encrypted results using the Wi-Fi module; if it is determined in the first determination step that the user voice signal has been inputted by the wireless relay device itself and if it is determined in the second determination step that the recipient to receive the user voice signal does not correspond to a member of a group operated by the wireless relay device, encrypting the user voice signal, and outputting the encrypted user voice signal using the radio transmission and reception unit; if it is determined in the first determination step that the user voice signal has not been inputted by the wireless relay device itself, determining in a third determination step whether or not the user voice signal has been received via the Wi-Fi module; if it is determined in the third determination step that the user voice signal has been received via the Wi-Fi module, determining in a fourth determination step whether or not the recipient to receive the user voice signal corresponds to the wireless relay device; if it is determined in the third determination step that the user voice signal has been received via the Wi-Fi module and if it is determined in the fourth determination step that the recipient to receive the user voice signal corresponds to the wireless relay device, decrypting the user voice signal and outputting the decrypted user voice signal using the voice I/O unit. receiving, by the wireless relay device, a user voice signal; determining in a first determination step whether or not the user voice signal has been inputted by the wireless relay device itself; if it is determined in the first determination step that the user voice signal has been inputted by the wireless relay device itself, determining in a second determination step whether or not a recipient to receive the user voice signal corresponds to a member (101A to 104A, 101B to 104B) of a group (A, B) operated by the wireless relay device; if it is determined in the first determination step that the user voice signal has been inputted by the wireless relay device itself and if it is determined in the second determination step that the recipient to receive the user voice signal corresponds to a member of a group operated by the wireless relay device, encrypting the user voice signal, and outputting the encrypted results using the Wi-Fi module; if it is determined in the first determination step that the user voice signal has been inputted by the wireless relay device itself and if it is determined in the second determination step that the recipient to receive the user voice signal does not correspond to a member of a group operated by the wireless relay device, encrypting the user voice signal, and outputting the encrypted user voice signal using the radio transmission and reception unit; if it is determined in the first determination step that the user voice signal has not been inputted by the wireless relay device itself, determining in a third determination step whether or not the user voice signal has been received via the Wi-Fi module; if it is determined in the third determination step that the user voice signal has been received via the Wi-Fi module, determining in a fourth determination step whether or not the recipient to receive the user voice signal corresponds to the wireless relay device; if it is determined in the third determination step that the user voice signal has been received via the Wi-Fi module and if it is determined in the fourth determination step that the recipient to receive the user voice signal corresponds to the wireless relay device, decrypting the user voice signal and outputting the decrypted user voice signal using the voice I/O unit.