I have a lot of accounts from an older version of a website that I need to migrate to a new version. Passwords are encrypted with bcrypt and I don't know what the salt was, what library, or anything like that. I only have the data from the database. What would be the best way to allow people to still use those accounts? One thought was the first time they try to login, send them an email getting them to update their password. Any other thoughts would be greatly appreciated. Project is running on MEAN stack if that matters.
UPDATE:
Is there a chance that it will just work? I tried an account that I knew the password for, and it seems to just work. Does bcrypt do some magic I am unaware of?