Or for paranoid encode also the password on SMS 
the script chgpass decode it and apply the correct password.
:cmd Vq70980q script chgpass KNHT6ICJOMQG63TFEBSXQYLNOBWGKLROFY======
Since the encoding can be arbitrary and not necessarly baseXX, is strong enough for detect failed try.
Encoding the password on that way allow the user to use also special characters not allowed on GSM7 alphabet…
http://forum.mikrotik.com/t/sms-charset-problem/74623/2