The safe way to do this is to check a password against a list of common passwords, as Jeff Atwood suggests [0] rather than against your other passwords. As othe

The safe way to do this is to check a password against a list of common passwords, as Jeff Atwood suggests [0] rather than against your other passwords. As other replies point out, you shouldn’t be able to compare your passwords’ plaintext to each other like you’re proposing[1]. [0]: https://blog.codinghorror.com/the-god-login/ https://blog.codinghorror.com/the-god-login/ [1]: I suppose you could salt and hash the user’s password against every other user’s password and their salt, but if you chose an appropriate password hash function and parameters, that would take infeasibly long. Edit: I missed that you essentially suggested this already. Sorry about that. However, I think the way Atwood explains it is useful.