I'm part of a team that's going to be migrating several older Drupal sites (Drupal 5, Drupal 6) into a new, single Drupal 7 site. I'm familiar with Drupal from a software architecture point of view, but not as familiar with the day to day running of a Drupal site as I'd like. Because of this I have a few general questions about this migration.
Are Drupal's password hashing mechanisms consistent across different versions?
If not, are there tools to support migrating user accounts and converting the passwords between versions?
If a no to migrations, are there modules that provide a standard experience for this situation that allows an old user to pick a new password?