How to find mac address in ios and android?

hi friends , for fetching mac address i read lot of forums and answers.i used that scripts i haven’t succeed.
static string GetMacAddress()
string macAddresses = “”;
foreach (NetworkInterface nic in NetworkInterface.GetAllNetworkInterfaces())
// Only consider Ethernet network interfaces, thereby ignoring any
// loopback devices etc.
if (nic.NetworkInterfaceType != NetworkInterfaceType.Ethernet) continue;
if (nic.OperationalStatus == OperationalStatus.Up)
macAddresses += nic.GetPhysicalAddress().ToString();
return macAddresses;
// Debug.Log ("deviceToken "+macAddresses);

i added namespaces

using UnityEngine;
using System.Collections;
using System.Net;
using System.Net.NetworkInformation;

when i run i am getting this error.
ArgumentException: length

If you want a unique identifier for a device use this: Unity - Scripting API: SystemInfo.deviceUniqueIdentifier