Did you get the solution? if Yes then could you please share with me.I am also getting the same problem.
Thanks in advance.
Guys, as you see from the java script tableau uses asymmetric encryption for password, thus, you can "capture" the password and even if you do you cannot use it again for obvious reasons. The server first sends the modulus and exponent then the your local browser encrypts your password (this is why it is not returned by the server, it is generated by your computer). Then, this encrypted password will be sent to the server. The server will always send different exponent and modulus ensuring you can't do anything with a sniffer encrypted value.
This is pretty standard way of web authentication.
As Diego linked I suggested two different methods in three different programming languages here: Re: How to capture the java script which generates the Crypted values for the password? You have so many ways to automate it, but you need something which will crypt the password based on the server's challenge.
Hope this helps.