How to show password which has dohash?

[eluser]shinokada[/eluser]
I input password in database with dohash 16 digits.

Now in an edit page of mine, I see the password with 16 black dots.

Q1. How can I undo the dohash so that 16 black dots becomes the number of original pw.

Q2. How can I see the original password so that I can read it?

Thanks in advance.