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Full Disk Encryption (FDE) Advice from a Reader

By Rich

I am doing some work on FDE (if you are using the Securosis Nexus, I just added a small section on it), and during my research one of our readers sent in some great advice.

Here are some suggestions from Guillaume Ross @gepeto42:


Things to Check before Deploying FDE

Support

  • Ensure the support staff that provides support during business days is able to troubleshoot any type of issue or view any type of logs. If the main development of the product is in a different timezone, ensure this will have no impact on support. I have witnessed situations where logs were in binary formats that support staff could not read. They had to be sent to developers on a different continent. The back and forth for a simple issue can quickly turn into weeks when you can only send and receive one message per day.

  • If you are planning a massive deployment, ensure the vendor has customers with similar types of deployments using similar methods of authentication.

Documentation

  • Look for a vendor who makes documentation available easily. This is no different than for any enterprise software, but due to the nature of encryption and the impact software with storage related drivers can have on your endpoint deployments and support, this is critical.

(Rich: Make sure the documentation is up to date and accurate. We had another reader report on a critical feature removed from a product but still in the documentation – which lead to every laptop being encrypted with the same key. Oops.)

Local and remote recovery

  • Some solutions offer a local recovery solution that allow the user to resolve forgotten password issues without having to call support to obtain a one time password. Think about what this means for security if it is based on “secret questions/answers”.

  • Test the remote recovery process and ensure support staff have the proper training on recovery.

Language

  • If you have to support users in multiple languages and/or multiple language configurations, ensure the solution you are purchasing has a method for detecting what keyboard should be used. It can be frustrating for users and support staff to realize a symbol isn’t in the same place on the default US keyboard and on a Canadian French keyboard. Test this.

(Rich: Some tools have on-screen keyboards now to deal with this. Multiple users have reported this as a major problem.)

Password complexity and expiration

  • If you sync with an external source such as Active Directory, consider the fact that most solutions offer offline pre-boot authentication only. This means that expired passwords combined with remote access solutions such as webmail, terminal services, etc. could create support issues.

Situation:

The user goes home. Brings his laptop. From home, on his own computer or tablet, uses an application published in Citrix, which prompts him to change his Active Directory password which expired.

The company laptop still has the old password cached.

Consider making passwords expire less often if you can afford it, and consider trading complexity for length as it can help avoid issues between minor keyboard mapping differences.

Management

  • Consider the management features offered by each vendor and see how they can be tied to your current endpoint management strategy. Most vendors offer easy ways to configure machines for automatic booting for a certain period or number of boots to help with patch management, but is that enough for you to perform an OS refresh?

  • Does the vendor provide all the information you need to build images with the proper drivers in them to refresh over an OS that has FDE enabled?

  • If you never perform OS refreshes and provide users with new computers that have the new OS, this could be a lesser concern. Otherwise, ask your vendor how you will upgrade encrypted workstations to the next big release of the OS.

Authentication

  • There are countless ways to deal with FDE authentication. It is very possible that multiple solutions need to be used in order to meet the security requirements of different types of workstations.

  • TPM: Some vendors support TPMs combined with a second factor (PIN or password) to store keys and some do not. Determine what your strategy will be for authentication. If you decide that you want to use TPM, be aware that the same computer, sold in different parts of the world, could have a different configuration when it comes to cryptographic components. Some computers sold in China would not have the TPM.

Apple computers do not include a TPM any more, so a hybrid solution might be required if you require cross-platform support.

  • USB Storage Key: A USB storage key is another method of storing the key separately from the hard drive. Users will leave these USB storage keys in their laptop bags. Ensure your second factor is secure enough. Assume USB storage will be easier to copy than a TPM or a smart card.

  • Password sync or just a password: A solution to avoid having users carry a USB stick or a smart card, and in the case of password sync, two different sets of credentials to get up and running. However, it involves synchronization as well as keyboard mapping issues. If using sync, it also means a simple phishing attack on a user’s domain account could lead to a stolen laptop being booted.

  • Smart cards: More computers now include smart card readers than ever before. As with USB and TPM, this is a neat way of keeping the keys separate from the hard drive. Ensure you have a second factor such as a PIN in case someone loses the whole bundle together.

  • Automatic booting: Most FDE solutions allow automatic booting for patch management purposes. While using it is often necessary, turning it on permanently would mean that everything needed to boot the computer is just one press of the power button away.

Miscellaneous bits

  • Depending on your environment, FDE on desktops can have value. However, do not rush to deploy it on workstations used by multiple users (meeting rooms, training, workstations used by multiple shifts) until you have decided on the authentication method.

  • Test your recovery process often.

  • If you will be deploying Windows 8 tablets in the near future, the availability of an on-screen keyboard that can work with a touchscreen could be important.

  • Standby and hibernation: Do not go through all the trouble of deploying FDE and then allow everyone to leave their laptop in standby for extended periods of time. On a Mac, set the standby delay to something shorter than the default. On Windows, disable standby completely. Prefer hibernation, and test that your FDE solution properly handles hibernation and authentication when booting back up.

  • On the other hand, if you were doing things such as clearing temp drives and pagefiles/swap for security or compliance reasons prior to that, ask yourself if it is still required. If you were wiping the Windows pagefile on shutdown to protect against offline attacks, it is probably not needed any more as the drive is encrypted. This can speed up shutting down considerably, especially on machines with a lot of RAM and a big page file.

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