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Anthony Ferrara's Blog: Properly Salting Passwords, The Case Against Pepper

Note: This article was originally published at PHPDeveloper on 18 April 2012.
PHPDeveloper

In this new post to his blog Anthony Ferrara looks at a common idea that comes up when the discussion of encryption of passwords in PHP - the global salt (or "pepper").

The other day I announced the release of my new password hashing library, PasswordLib. As I've come to expect, Reddit was full of interesting commentary on the topic. Some was good, some was bad and some surprised me. What surprised me was the insistence on a global salt (otherwise known as a "pepper"). So, I started thinking about it some more, and I figured I'd write a post on why I don't use peppers in my hashing algorithms (and why you may want to rethink it too).

He starts with an explanation of what a salt is (and isn't) to lead naturally into the idea of a "pepper", a single unique value that's used across an entire site/application for password encryption. He covers four flaws inherent with this method:

  • There's no proof that using them increases your security.
  • There are no publicly vetted hashing algorithms that accept a pepper as an argument.
  • Using a block cipher instead of a pepper provides a stronger level of encryption and protection.
  • The entire concept of a pepper is based around a flawed premise. [...] The flaw in that premise is that it's often not just your database that's leaked.