Windows 7, Security, and the Trusted Platform Module

Print
Check out this page on Dell.com! Email
Rate
1 out of 5
2 out of 5
3 out of 5
4 out of 5
5 out of 5

By: Steven J. Vaughan-Nichols (3/22/2010)

Every Windows expert knows that the way to secure a hard drive in Windows 7 is to use BitLocker. To use that feature, though, you need either Windows 7 Enterprise or Ultimate. But, did you ever wonder how BitLocker manages to lock down data when so much of Windows is vulnerable to attacks? Here’s how Microsoft has managed to make BitLocker easily the most secure part of Windows. Back in 2001, Microsoft began working on an encrypted security project called Palladium, which soon became known as Next-Generation Secure Computing Base (NGSCB). While Microsoft has said hardly a word about NGSCB over the last few years, it’s clearly become the basis of Windows 7’s TPM (Trusted Platform Module). In turn, TPM is at the core of BitLocker. In NGSCB everything on the computer, data and programs, can be encrypted. Only trusted processes can access disk storage, CPU memory space, and main memory. In practice, Microsoft has opted to only make NGSCB security available for BitLocker. In Windows 7, Microsoft uses TPM 1.2 software to interact with computer’s built-in TPM 1.2 chips. Each PC’s TPM processor comes with a unique RSA encrypted key. In Windows, this is called the Storage Root Key (SRK). The private TPM key is never exposed to any other component, software, process, or person. You should keep in mind that the Windows 7 (and Server 2008 R2 for that matter) version of BitLocker won’t work with TPM 1.1 or earlier hardware. In addition, your computer must have a Trusted Computing Group (TCG)-compliant BIOS, and the BIOS must be set both to boot first from the hard disk (not the USB or CD drives) and also to read from a USB flash drive during the startup. You also need a minimum of two drive partitions. To see if your software is ready to go with BitLocker, you first need to check that you have the right TPM driver. To do that, click Start, type `devmgmt.msc` in the Search programs and files box, and then press ENTER to open Device Manager. Right-click the TPM, and click Properties. Click the Driver tab, and verify that the Driver Provider field displays Microsoft. Next, to make sure that your hardware is up to the job, get to the Control Panel, click System and Security, click BitLocker Drive Encryption, and then click Turn On BitLocker. If your computer does not have a TPM version 1.2 or the BIOS is not compatible with the TPM, you’ll receive the following error message: A compatible Trusted Platform Module (TPM) Security Device must be present on this computer, but a TPM was not found. Please contact your system administrator to enable BitLocker. You may still be in luck though. Some systems ship with the TPM chip disabled. If that’s the case, you should be able to turn it on through the BIOS. You can also use BitLocker without a TPM chip, although it’s far less secure. To do so, according to Microsoft, you must enable the Require additional authentication at setup Group Policy setting, which is located in Computer Configuration\Administrative Templates\Windows Components\BitLocker Drive Encryption\Operating System Drives. You must select the Allow BitLocker without a compatible TPM check box. After this setting is applied to the local computer, the non-TPM settings appear in the BitLocker setup wizard. The encryption key, in this case, is kept on a USB-Flash drive that must be mounted during the system boot-up. In addition to not being as secure with this setup, BitLocker also runs slower. That’s because the TPM contains a cryptographic co-processor, besides providing secure storage for cryptographic keys. So, for example, when you read a file from a BitLocker-protected directory, the translation of the file into a human readable form from its encrypted format is done not by your PC’s CPU but by the TPM chip. Windows 7 uses the TPM to create cryptographic keys and to encrypt them so that they can be decrypted only by the TPM that created it. This process is called “wrapping” or “binding.” These are the “public” keys that can be used to unlock secured files. In addition, these keys are tied to specific platform measurements. So to unlock, or “unseal” a BitLocker secured file, you must use the computer on which it was generated. And, alas, if that machine has been altered significantly, say a change in memory and a processor upgrade, it may not be able to read the secured file. Since the TPM uses its own internal firmware, totally private key, and logic circuits for processing instructions, it does not rely upon the operating system. This blocks it from most, not all, attempts to break into it and the files it’s been used to secure. Attacks made by rootkits that get to the PC during the boot can take a system over before TPM is loaded. Windows 7 uses the TPM’s public key to unlock data that’s been encrypted data into a TC (trusted computing) space, sometimes called the vault. This vault, although often described as physically isolated from the rest of the computer, actually runs on the same hardware. When you use it, however, a separate memory area is set aside for use by the encryption routines and data. Here’s how it works in more detail. When you try to open a BitLocker encrypted file, Windows 7 calls up Nexus, a security kernel that’s part of Windows 7. In turn only Nexus Computing Agents (NCAs), trusted modules can run under Nexus. This kernel and the NCAs run within a protected memory space that’s reserved only for TPM-protected data and programs. NCAs have access to only a subset of the Windows Application Programming Interface (API). It’s because of this that the only program that really makes use of TPM and the security it provides is BitLocker. While in theory, you could write applications that ran in an encrypted mode, the Windows API, which has evolved over the years, is far too messy to work well in this ultra-secure environment. However, one common use of TPM technology that we may see in the future in Windows, via add-on programs such as Silverlight, is digital rights management (DRM), better known to its enemies as digital restrictions management. TPM chips are already used in some consumer devices to restrict video playback. Microsoft is already using PlayReady, to encrypt Sliverlight video and audio content on some devices. It would be easy to require its use on Windows PCs in conjunction with TPM hardware. You can look for this expansion in the next few years as TPM software and hardware goes more mainstream. In the meantime though if you really want to secure your data, and you have the right hardware and Windows 7 editions, TPM-enabled BitLocker is the way to go.

Every Windows expert knows that the way to secure a hard drive in Windows 7 is to use BitLocker. To use that feature, though, you need either Windows 7 Enterprise or Ultimate. But, did you ever wonder how BitLocker manages to lock down data when so much of Windows is vulnerable to attacks? Here’s how Microsoft has managed to make BitLocker easily the most secure part of Windows.

Back in 2001, Microsoft began working on an encrypted security project called Palladium, which soon became known as Next-Generation Secure Computing Base (NGSCB). While Microsoft has said hardly a word about NGSCB over the last few years, it’s clearly become the basis of Windows 7’s TPM (Trusted Platform Module). In turn, TPM is at the core of BitLocker.

In NGSCB everything on the computer, data and programs, can be encrypted. Only trusted processes can access disk storage, CPU memory space, and main memory. In practice, Microsoft has opted to only make NGSCB security available for BitLocker.

In Windows 7, Microsoft uses TPM 1.2 software to interact with computer’s built-in TPM 1.2 chips. Each PC’s TPM processor comes with a unique RSA encrypted key. In Windows, this is called the Storage Root Key (SRK). The private TPM key is never exposed to any other component, software, process, or person. You should keep in mind that the Windows 7 (and Server 2008 R2 for that matter) version of BitLocker won’t work with TPM 1.1 or earlier hardware.

In addition, your computer must have a Trusted Computing Group (TCG)-compliant BIOS, and the BIOS must be set both to boot first from the hard disk (not the USB or CD drives) and also to read from a USB flash drive during the startup. You also need a minimum of two drive partitions.

To see if your software is ready to go with BitLocker, you first need to check that you have the right TPM driver. To do that, click Start, type devmgmt.msc in the Search programs and files box, and then press ENTER to open Device Manager. Right-click the TPM, and click Properties. Click the Driver tab, and verify that the Driver Provider field displays Microsoft.

Next, to make sure that your hardware is up to the job, get to the Control Panel, click System and Security, click BitLocker Drive Encryption, and then click Turn On BitLocker. If your computer does not have a TPM version 1.2 or the BIOS is not compatible with the TPM, you’ll receive the following error message:

A compatible Trusted Platform Module (TPM) Security Device must be present on this computer, but a TPM was not found. Please contact your system administrator to enable BitLocker.

You may still be in luck though. Some systems ship with the TPM chip disabled. If that’s the case, you should be able to turn it on through the BIOS.

You can also use BitLocker without a TPM chip, although it’s far less secure. To do so, according to Microsoft, you must enable the Require additional authentication at setup Group Policy setting, which is located in Computer Configuration\Administrative Templates\Windows Components\BitLocker Drive Encryption\Operating System Drives. You must select the Allow BitLocker without a compatible TPM check box. After this setting is applied to the local computer, the non-TPM settings appear in the BitLocker setup wizard. The encryption key, in this case, is kept on a USB-Flash drive that must be mounted during the system boot-up.

In addition to not being as secure with this setup, BitLocker also runs slower. That’s because the TPM contains a cryptographic co-processor, besides providing secure storage for cryptographic keys. So, for example, when you read a file from a BitLocker-protected directory, the translation of the file into a human readable form from its encrypted format is done not by your PC’s CPU but by the TPM chip.

Windows 7 uses the TPM to create cryptographic keys and to encrypt them so that they can be decrypted only by the TPM that created it. This process is called “wrapping” or “binding.” These are the “public” keys that can be used to unlock secured files. In addition, these keys are tied to specific platform measurements. So to unlock, or “unseal” a BitLocker secured file, you must use the computer on which it was generated. And, alas, if that machine has been altered significantly, say a change in memory and a processor upgrade, it may not be able to read the secured file.

Since the TPM uses its own internal firmware, totally private key, and logic circuits for processing instructions, it does not rely upon the operating system. This blocks it from most, not all, attempts to break into it and the files it’s been used to secure. Attacks made by rootkits that get to the PC during the boot can take a system over before TPM is loaded.

Windows 7 uses the TPM’s public key to unlock data that’s been encrypted data into a TC (trusted computing) space, sometimes called the vault. This vault, although often described as physically isolated from the rest of the computer, actually runs on the same hardware. When you use it, however, a separate memory area is set aside for use by the encryption routines and data.

Here’s how it works in more detail. When you try to open a BitLocker encrypted file, Windows 7 calls up Nexus, a security kernel that’s part of Windows 7. In turn only Nexus Computing Agents (NCAs), trusted modules can run under Nexus. This kernel and the NCAs run within a protected memory space that’s reserved only for TPM-protected data and programs.

NCAs have access to only a subset of the Windows Application Programming Interface (API). It’s because of this that the only program that really makes use of TPM and the security it provides is BitLocker. While in theory, you could write applications that ran in an encrypted mode, the Windows API, which has evolved over the years, is far too messy to work well in this ultra-secure environment.

However, one common use of TPM technology that we may see in the future in Windows, via add-on programs such as Silverlight, is digital rights management (DRM), better known to its enemies as digital restrictions management. TPM chips are already used in some consumer devices to restrict video playback.

Microsoft is already using PlayReady, to encrypt Sliverlight video and audio content on some devices. It would be easy to require its use on Windows PCs in conjunction with TPM hardware.

You can look for this expansion in the next few years as TPM software and hardware goes more mainstream. In the meantime though if you really want to secure your data, and you have the right hardware and Windows 7 editions, TPM-enabled BitLocker is the way to go.