How to Hack Wi Fi Using Android

It is easy as piece of cake but you have to root your mobile which is risky, so here are some some step you should follow,
                            these tools are available for free as long as your device is compatible. Hacking routers without permission is illegal. 
WEP Routers
and
Download bcmon.   
 1. This tool enables Monitor Mode on your Broadcom chipset, which is essential for being able to crack the PIN. The bcmon APK file is available for free from the bcmon page on the Google Code website.

• To install an APK file, you will need to allow installation from unknown sources in your Security menu. Step 2 of this article goes into more detail

 2. After installing the APK file, run the app. If prompted, install the firmware and tools. Tap the "Enable Monitor Mode" option. If the app crashes, open it and try again. If it fails for a third time, your device is most likely not supported.

• Your device must be rooted in order to run bcmon.

3. This will launch a terminal similar to most Linux terminals.Type airodump-ng and tap the Enter button. AIrdump will load, and you will be taken to the command prompt again. Type airodump-ng wlan0 and tap the Enter button.

4.Now  You will see a list of available access points. You must select an access point that is using WEP encryption.

This is the MAC address for the router. Make sure that you have the right one if there are multiple routers listed. Jot this MAC address down.

• Also note the Channel that the access point is broadcasting on.
• You will need to collect information from the access point for several hours before you can attempt to crack the password. Typeairodump-ng -c channel# --bssid MAC address -w output ath0and tap Enter. Airodump will begin scanning. You can leave the device for a while as it scans for information. Be sure to plug it in if you are running low on battery.
• Replace channel# with the channel number the access point is broadcasting on (e.g. 6).
• Replace MAC address with the MAC address of the router (e.g 00:0a:95:9d:68:16)
• Keep scanning until you reach at least 20,000-30,000 packets.

5.Once you have a suitable number of packets, you can start attempting to crack the password . Return to the terminal and type aircrack-ng output*.cap and tap Enter.

6.After the cracking process is complete (which could take several hours), the message Key Found! will appear, followed by the key in hexadecimal form. Make sure that "Probability" is 100% or the key will not work.^[1]

• When you enter the key, enter it without the ":". For example, if the key was 12:34:56:78:90, you would enter 1234567890.