Sql bulk password salting

Hello,

I have inherited a legacy db which stored unencryped passwords, as part the upgarde process i woul rather if possible not have to email all of our users asking them to change thier password.

The updated system uses the membershipprovider & sha1.

What i need to know is is there anyway to replicated what .net is doing in the function below in pure sql to migrate about 4000 users in one go. 

i appreciate the random number is erm random, but as .net can read & write the password it followins it must be possible to reblicte this is sql server if you have all the keys.

 

   private string TransformPassword(string password, ref string salt)
        {
            string ret = string.Empty;

            switch (PasswordFormat)
&nbs ...