Column Encryption

We want to encrypt one of the password column.We can hast the column values,The biggest challenge is we have

few user having read only access to the DB ,so if somebody will get the encryption key ,They can easily crack

the password.Some of the application need to decrypt the values which they use for authentication.

TDE would have been a solution for it ,but unfortunately this is a licensed option.Any other suggestion !

Thanks

Suvv