How to migrate user passwords from D6 to D7 site using salt module? I need to migrate the user passwords from Drupal 6 site to Drupal 7 Website. I am using the migrate_d2d module for performing the migrations. But the problem I am facing is that the Drupal 6 site uses the salt module which appends an internal string to the users passwords before it is being saved to the database. So migrating the passwords as such doesn't work. 

Can any one tell me if there is some way to migrate the user passwords in this case or its not possible??
It is not possible - both Drupal version stores user passwords in a way that was considered pretty secure when the major version was released. But these ways are incompatible. And by design you cannot recover passwords - it's a one way algorithm. Well, there are ways to hack passwords from D6 now (that's why it was changed in D7) but they are CPU-intensive, and in some countries attempts are outright illegal.

The best you can do is to use _user_mail_notify($op, $account, $language = NULL) - Set $op to 'password_reset' and call it inside foreach over all accounts after migration. That way all users will get an email saying they need to reset their password, with one-time link to do that. Probably there is already a module for that, too, but I couldn't find it.