Password Form Usability: Duke Energy

When you’re singing up with any online service, picking a password is always trouble. What weird password requirements does this service have? Tonight I had that question with Duke Energy’s sign-up form. Fortunately, they had a Help icon that described the password rules:

Duke Energy Sign-up Form: password rules
Text reads: Password are case-sensitive and must contain at least eight letters or numbers.

OK, minimum of 8 alphanumeric characters. Easy enough.

I use Password Safe as my password manager. I have no idea what any of my passwords are: they are auto-generated random strings. I generated a new random password and entered it into the form:

Duke Energy Form: password feedback mixed messages
Text reads: Must be at least eight characters, contain one letter and one number and no special characters.

OK, so the password rules are a little different than what was initially described. But which symbols are special characters? And this screen is sending mixed-messages: if the password strength is rated Strong, why is it not valid?

I updated the password generation rules in Password Safe to generate a new password, assuming that only alphanumeric characters are allowed:

  • Use lowercase letters, minimum 1
  • Use upper case letters, no minimum
  • Use numbers, minimum 1
  • No symbols

And, since no symbols are included, I increased the password length to 16 characters. This new password was accepted, but the feedback indicates that the password is only moderately strong!

Duke Energy form: a valid password, rated moderately strong
The password is valid, but rated only moderately strong

I’m guessing that the code that generates the password strength indicator is from a 3rd-party and has no knowledge of Duke Energy’s password rules.

My problems with this, from a usability perspective:

  1. The password rules should apparent and described accurately.
  2. The password strength indicator should be aware of any password rules, and should describe a rejected password as such.

From a security perspective, I don’t see why any keyboard characters should be restricted. More characters to choose from means more complexity. Plus, if there were no character restrictions, it would be easier to describe the rules–and use an accurate 3rd-party password-strength tool.

Encrypted versus hashed passwords

I’m trying to decide whether it is better to store passwords in a database as key-encrypted strings, or as the result of a hash function (with salt).


An encrypted string is secure as long as the key is secure, which it seems to me is both its strength and its Achilles’ heel. Since the application that accesses the database needs to use the key, that means that if both the database and the application server are compromised, the data is compromised.

It also means that if the application developers have access to the database, or if the DBAs have access to the application code, the data is available to those individuals. Even though those users are most likely trustworthy, it is perhaps an unnecessary risk–not to mention their workstations may be compromised. On top of that, you need to worry about key escrow–if you lose the key, you no longer have access to your own data.

A hashed value is secure even if the database and the application are compromised, as it is the result of a one-way function. The value is also inaccessible to either the application developers or the DBAs, which provides an additional layer of security. On the other hand, since it uses a well-known hash function, such as MD5, creating a dictionary file of hashed values is trivial, and apparently an even more effective method to reveal hashed data is to use a rainbow table (the description of which goes a bit over my head right now).

That’s where the salt comes in: concatenate the original value along with extra data before creating the hash. I can see how this would foil a simple dictionary of hashed values. From what I’ve read, the salt value can be unique for each hashed value, and can be stored alongside the hashed value in the database. I’m not sure I entirely understand how that defends against rainbow tables, but it sounds good to me.

Using a hashed value, you can’t retrieve the original data–you can only match against it. This would not work well for data that you need to access again in its original form, e.g. phone numbers. This is a drawback in some cases, but probably not for passwords.

Right now I’m leaning towards salted hash over encryption, but maybe that’s because I’m hungry and it sounds more like breakfast. I’d love to know what other people think.