Introduction To Database Encryption - The Reboot!By Adrian Lane
Updated June 4th to reflect terminology change.
This is the Re-Introduction to our Database Encryption series. Why are we re-introducing this series? I’m glad you asked. The more we worked on the separation of duties and key management sections, the more dissatisfied we became. Rich and I got some really good feedback from vendors and end users, and we felt we were missing the mark with this series. And not just because the stuff I drafted when I was sick completely lacked clarity of thought, but there are three specific reasons we were unhappy. The advice we were giving was not particularly pragmatic, the terminology we thought worked didn’t, and we were doing a poor job of aligning end-user goals with available options. So yeah, this is an apology to our audience as the series was not up to our expectations and we failed to achieve some of our own Totally Transparent Research concepts. But we’re ‘fessing up to the problem and starting from scratch.
So we want to fix these things in two ways. First we want to change some of the terminology we have been using to describe database encryption. Using ‘media encryption’ and ‘separation of duties’ is confusing the issues, and we want to differentiate between the threat we are trying to protect against vs. what is being encrypted. And as we are talking to IT, developers, DBAs, and other audiences, we wanted to reduce confusion as much as possible. Second, we will create a simple guide for people to select a database encryption strategy that addresses their goals. Basically we are going to outline a decision tree of user requirements and map those to the available database encryption choices. Rich and I think that will aid end users to both clarify their goals and determine the correct implementation strategy.
In our original introduction we provided a clear idea of where we wanted to go with this series, but we did adopt our own terminology in order to better encapsulate the database encryption options vendors provide. We chose “Encryption for Separation of Duties” and “Encryption for Media Protection”. This is a bit of an oversimplification, and mapped to the threat rather than to the feature. Plus, if you asked your RDBMS vendor for ‘media encryption’, they would not know what they heck you were talking about. We are going to change the terminology back to the following:
DatabaseTransparent/External Encryption: Encryption of the entire database. This is provided by native encryption functions within the database. The goal is to prevent exposure of information due to loss of the physical media. This can also be done through drive or OS/file system encryption, although they lack some of the protections of native database encryption. The encryption is invisible to the application and does not require alterations to the code or schema. DataUser Encryption: Encrypting specific columns, tables, or even data elements in the database. The classic example is credit card numbers. The goal is to provide protection against inadvertent disclosure, or to enforce separation of duties. How this is accomplished will depend upon how key management is utilized and (internal/external) encryption services, and will affect the way the application uses the database, but provides more granular access control. While we’re confident we’ve described the two options accurately, we’re not convinced the specific terms “database encryption” and “data encryption” are necessarily the best, so please suggest any better options.
Blanket encryption of all database content for media protection is much easier than encrypting specific columns & tables for separation of duties, but it doesn’t offer the same security benefits. Knowing which to choose will depend upon three things:
- What do you want to protect?
- What do you want to protect it from?
- What application changes and management tasks will you tolerate?
Thus, the first thing we need to decide when looking at database encryption is what are we trying to protect and why. If we’re just going after the ‘PCI checkbox’ or are worried about losing data from swapping out hard drives, someone stealing the files off the server, or misplacing backup tapes, then database encryption (for media protection) is our answer. If the goal is to protect data in the event of compromised accounts, rogue DBAs, or inadvertent disclosure; then things get a lot more complicated. We will go into the details of ‘why’ and ‘how’ in a future post, as well as the issues of application alterations, after we have introduced the decision tree overview. If you have any comments, good, bad, or indifferent, please share. As always, we want the discussion to be as open as possible.