Managing Windows Server 2012 Storage and File Systems : TPM and BitLocker Drive Encryption (part 1) - Understanding TPM states and tools

Current Windows and Windows Server operating systems include the Encrypting File System (EFS) for encrypting files and folders. Using EFS, users can protect sensitive data so that it can be accessed only by using their public key certificate. Encryption certificates are stored as part of the data in a user’s profile. As long as users have access to their profiles and the encryption keys they contain, they can access their encrypted files.

Although EFS offers excellent protection for your data, it doesn’t necessarily safeguard the computer from attack by someone who has direct physical access. In a situation where a user loses a computer, a computer has been stolen, or the attacker is logging on to a computer, EFS might not protect the data because the attacker might be able to gain access to the computer before it boots. He could then access the computer from another operating system and change the computer’s configuration. He might then be able to hack into a logon account on the original operating system so that he can log on as the user or configure the computer so that he can log on as a local administrator. If he can do this without having to reset the password of the user who encrypted the files or the administrator, the attacker could eventually gain full access to a computer and its encrypted data.

To seal a computer from physical attack and wrap it in an additional layer of protection, current Windows and Windows Server operating systems include the Trusted Platform Module (TPM) Services architecture. TPM Services protect a computer using a dedicated hardware component called a TPM. A TPM is a microchip that is usually installed on the motherboard of a computer where it communicates with the rest of the system using a hardware bus. Computers can use a TPM to provide enhanced protection for data, to ensure early validation of the boot file’s integrity, and to guarantee that a disk has not been tampered with while the operating system was offline.

A TPM has the ability to create cryptographic keys and encrypt them so that they can be decrypted only by the TPM. This process, referred to as wrapping or binding, protects the key from disclosure. A TPM has a master “wrapping” key called the Storage Root Key (SRK). The SRK is stored within the TPM itself to ensure that the private portion of the key is secure.

Computers that have a TPM can create a key that has not only been wrapped but also sealed. The process of sealing the key ensures the key is tied to specific platform measurements and can be unwrapped only when those platform measurements have the same values that they had when the key was created. This is what gives TPM-equipped computers increased resistance to attack.

Because TPM stores private portions of key pairs separately from memory controlled by the operating system, keys can be sealed to the TPM to provide absolute assurances about the state of a system and its trustworthiness. TPM keys are unsealed only when the integrity of the system is intact. Further, because the TPM uses its own internal firmware and logical circuits for processing instructions, it does not rely upon the operating system and is not subject to external software vulnerabilities.

The TPM can also be used to seal and unseal data that is generated outside of the TPM, and this is where the true power of the TPM lies. In current Windows and Windows Server operating systems, the feature that accesses the TPM and uses it to seal a computer is called BitLocker Drive Encryption. Although BitLocker Drive Encryption can be used in both TPM or non-TPM configurations, the most secure method is to use TPM.

When you use BitLocker Drive Encryption and a TPM to seal the boot manager and boot files of a computer, the boot manager and boot files can be unsealed only if they are unchanged since they were last sealed. This means you can use the TPM to validate a computer’s boot files in the pre-operating system environment. When you seal a hard disk using TPM, the hard disk can be unsealed only if the data on the disk is unchanged since it was last sealed. This guarantees that a disk has not been tampered with while the operating system was offline.

When you use BitLocker Drive Encryption and do not use TPM to seal the boot manager and boot files of a computer, TPM cannot be used to validate a computer’s boot files in the pre-operating system environment. This means there is no way to guarantee the integrity of the boot manager and boot files of a computer.

The TPM Services architecture provides the basic features required to configure and deploy TPM-equipped computers. This architecture can be extended with a feature called BitLocker Drive Encryption.

Before you can use TPM, you must turn on TPM in firmware and initialize the TPM for first use in software. As part of the initialization process, you set the owner password on the TPM. After TPM is enabled, you can manage the TPM configuration.

In some cases, computers that have TPM might ship with TPM turned off. If so, you must turn on TPM in firmware. With one of my computers, I needed to do the following:

Next, you need to initialize and prepare the TPM for first use in software. As part of this process, you take ownership of the TPM, which sets the owner password on the TPM. After TPM is enabled, you can manage the TPM configuration. Several tools for working with TPM are available:

When you are working with the Trusted Platform Module Management, you’ll be able to determine the exact state of the TPM. If you try to start Trusted Platform Module Management without turning on TPM, you’ll see an error like the one shown in Figure 1.

Figure 1. An error occurs when you start the Trusted Platform Module Management without turning on TPM.

Similarly, if you try to run Manage The TPM Security Hardware without turning on TPM, you’ll see an error like the one shown in Figure 2.

Figure 2. An error occurs when you try to run Manage The TPM Security Hardware without turning on TPM.

Only when you’ve turned on TPM in firmware will you be able to access and work with the TPM tools. When you are working with the Trusted Platform Module Management console, shown in Figure 3, you should note the TPM status and the TPM manufacturer information. The TPM status indicates the state of the TPM. The TPM manufacturer information shows whether the TPM supports specification version 1.2 or 2.0. Support for TPM version 1.2 or later is required.

Figure 3. Use the Trusted Platform Module Management console to initialize and manage TPM.

Although earlier releases of Windows showed the exact TPM state as listed in Table 1, Windows 8 and Windows Server 2012 normally show either a status of “The TPM is ready for use” or “The TPM is not ready for use.” If the TPM is ready for use, the TPM is on and ownership has been taken.