title: Trying to compare password history to hashed passwords created by SqlMembershipProvider
body: <p>I am using a SqlMembershipProvider and storing my passwords as hashed.  I am also keeping a history of the (hashed) passwords in another table.  I want to be able to compare the password a user tries to change their password to, to their old passwords and throw an error if it was too recent.  I do not seem to be able to figure out how to use the hashing functions to do this.  Basically what I am looking for is a method like this:</p>
  
  <pre><code>public bool PasswordCompare(string plaintextPassword, string salt, string hashedPassword)
  {
      //where the salt and hashedPassword are pulled out of the aspnet_Membership table
      //which are automatically generated by the provider
  }
  </code></pre>
  
  <p>I hope this is clear, thank you.</p>