I have an existing database with about 1.6 million users in it. Currently the passwords are stored as salted SHA1, I'd like to upgrade them all to salted SHA256.
The approach I've taken so far if to migrate each user as they login, essentially validate their password against the old hash and if it matches create a new stronger hash. This works fine, but it's a slow process.
As far as I can see there is no easy way to shortcut this process. Is there a better way?