Question

I’m trying to secure a website that is being moved to a public server soon. I’ve just finished adding the password hashing functions to all of my login scripts. I’m using FormsAuthentication.HashPasswordForStoringInConfigFile(pw, method) to do so. I have a question about the process I’m using and whether or not it’s secure for a web server:

1. Password is sent in plain text over HTTPS to the server
2. The server looks in the Users table to find the user’s Salt (several random characters) and their hashed and salted stored password
3. The plain text password is appended with the Salt
4. The new string is hashed using the above function
5. The newly hashed version is compared to the stored version
6. If equal, login is allowed
7. If not equal, the login attempt is logged in Session variables, up to 3 times before locking out the user’s machine from accessing the login page until an admin verifies IP address and unlocks.

Does this look about right? I just don’t see how the salt is effective in this method… Anyway, all I’ve done is add a salt and hash. Is this considered Encryption? Or am I missing a step? I remember reading that hashing algorithms like SHA1 and MD5 are not encyption algorithms, so what else needs to be done?

Answer 1

That is correct. The salt is used to prevent rainbow table attacks where a dictionary of common works hashed with MD5 is used to try to gain entry. Using the salt ensures that even if they had an MD5 hash of the word, it wouldn’t work because they don’t know the salt.

The MD5 algorithm is a 1 way hash algorithm, and not an encryption value. The difference is, once you’ve hashed the value, there is no way to get back to the original value. Encryption allows you to decrypt the data and get back the original value. So you are correct, they are not the same, and your passwords are not encrypted, they are hashed. This means that if someone forgets their password, you cannot send it to them. You have to provide a way for them to reset their password instead. This also means that anyone with access to the database would not have access to raw passwords. Which is good because a lot of people use the same password everywhere, and if you had access to a large list of usernames and passwords, someone could decide to start trying to log into bank / credit card websites.

What you are doing is a recommended practice.