Using PIN instead of a password for encryption on Galaxy S3
It is not possible to change the PIN any more in the settings because everything except the alpha numeric password is greyed out. The solution is Tasker together with Secure Settings:
Create a task "ChangePin", add an Action "Plugin", "Secure Settings" and choose "Password/Pin" under "Dev Admin Actions" as Action. Choose "Enabled", "Pin Code" and enter the new Pin code, then run the task.
This action will also change the encryption password to the weak PIN, so proceed to the next section. For more details you can check at Samsung India site in its support option.