International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 5, May 2013)
Securing a Firm’s Computer Operating System: Trusted
Platform Module
Hak J. Kim1
1
Hofstra University, Hempstead, NY11549
Abstract— Recently Trusted Platform Module (TPM) is
emerged as a new solution to secure computers and other
systems. It is a small microchip that enables encryption and
stores authentication information in computer motherboard.
This paper presents the initiative of trust computing and an
overview of TPM along with architecture and security
features. We also discuss the applications and future of TPM.
In summary, the TPM is becoming a viable and recognized
approach for implementing security controls for embedded
systems. With strong vendor adoption, the potential of TPM is
tremendous and the continued development of TPM is
essential.
II. TRUSTED COMPUTING INITIATIVE
In July 2007, the Department of Defense (DoD) created
new policy that protects sensitive unclassified data-at-rest.
The new policy stated the following [4]:
“In anticipation of emerging encryption product
capabilities as well as requirements for device
authentication, DoD Components shall ensure all
new computer assets (i.e. server, desktop, laptop and
PDA) procured to support the DoD enterprise
include a Trusted Platform Module version 1.2 or
higher where such technology is available.” – James
R. Clapper Jr., Director of National Intelligence.
This initiative is taken up by the Trusted Computing
Group (TCG) and their efforts to develop open
specifications for building blocks that enable secure
computing (Dinesh, 2005). The TCG creates a specification
for an embeddable microcontroller to provide a number of
security services for the benefit of its host platform. These
specifications have now been implemented by a number of
IC vendors. While TPM functionality is not tied to any
specific type of platform, the adoption by PC vendors has
been extremely significant. Nearly all of the world’s
leading PC vendors have TPM chips integrated in their PCs
[5].
Keywords—operating system, trusted computing, trusted
platform module
I. INTRODUCTION
Since the Internet has been a part of nearly every facet of
our lives, our world becomes increasingly more reliant on
the networked computers. According to ITU [1], the Internet
usage in 2011 was about seven billion people which are
nearly one third of world population.
As the uses for the Internet expand, so does the need for
security. Security expends great effort on authenticating
users; for example, who a user is, what access they should
be permitted, and what authority they may exert. However,
instead of software-based authentication, more basic and
important responsibility is to authenticate hardware on
which information systems depend.
The Internet users often struggle to manage multiple
passwords and login information in computers. For solving
this problem, recently a new way of securing computer
hardware is introduced which is called Trusted Platform
Module (TPM) [2]. The TPM is a little chip of silicon that
authenticates computing devices themselves. It tries to
simplify a computer’s passwords and authentication
mechanisms into a single sign-on capability [3]. Over 150
million computers between 2006 and 2007 were reported as
preinstalled by the manufacturer with TPM chips.
In this paper, we present the concept of trusted
computing and explore the TPM with architecture,
components, and applications. We also discuss its issues
and challenges.
III. A BRIEF OVERVIEW OF TPM
A. What is TPM?
As addressed in the above, the TPM is created by an
alliance of computing companies (TCG) to provide for the
availability of computers and to ensure data confidentiality
and integrity on computers and networks [6]. It is made up
of a microcontroller that enables encryption and stores
authentication devices.
The TPM is executed in the motherboard of personal
computers and notebooks and is supported by multiple
applications, such as BitLocker that runs on the Microsoft
Windows Operating System. It is used both in the private
and public sector. The TPM supports security within the
computer system with which it is paired and works with
software, hardware and firmware to prevent unauthorized
access to a computer.
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International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 5, May 2013)
There are several vulnerabilities associated with TPM
that when exploited, decrease the integrity of the program.
Future versions of TPM promise enhanced functionality
and performance.
Its purpose is to provide an encrypted wrapper around
private keys which are stored outside of the TPM. The
owner authentication key a secret value up to 160 bytes
which is created by the owner upon taking ownership of a
TPM enabled device and is used when authenticating
sensitive requests initiated by the hardware owner.
3) Volatile Memory: It contains RSA key slots, platform
configuration register, key handles, and authentication
service handlers. The RSA key slot, labeled 0-9, is a
temporary storage which is earmarked for additional key
pairs as they are exported and imported into memory.
Platform Configuration Registers are used to store hashes
of the software boot chain in a secure fashion. They are
null prior to initialization, 160 bytes in size and labeled 015; registers 0-7 are used for TPM use whereas registers 815 are reserved for operating system and application usage.
(Schellekens et al., 2008).
There are two types of handles in volatile memory. Key
handles distribute unique names to each loaded key so that
any commends can call on the key by using its unique
name. Once a loaded key is no longer in use, Key handles
clear that key from memory. Authorization session handles
identify authorization state data across many commands.
4) Attestation Identity Key: Although physically stored
outside of the TPM, Attestation Identify keys (AIK) are a
vital part of the TPM. They are generated and managed by
the TPM for the purpose of privacy protection, platform
authentication and collusion prevention. To that end, TPMs
have many AIK keys active at any given time.
When the TPM is required to authenticate itself to a
verifier, a second RSA key is generated, which is the AIK.
Next, the AIK’s public key is sent to the Privacy CA,
which then authenticates the AIK public key with the
TPM’s Endorsement key. Next, the Privacy CA checks if
the EK is on their list; if so, then a certificate is issued on
the TPM’s presented AIK. Conversely, a certificate is not
issued if the EK is not found. Finally, the TPM forwards
the newly received certificate to the verifier and
authenticates itself with the AIK. This is referred to as
remote attestation as a remote platform requests proof of
the current platform’s configuration (Brickell et al, 2004).
5) Opt-in and Execution: The Opt-In component also
resides outside of the physical TPM and it is responsible
for ensuring that state of each TPM component is in the
state specified by the end user, per Trusted Computing
Group’s policy. Upon ordering TPM-enabled hardware, the
customer may select to have certain TPM components
disabled, deactivated or fully enabled when initially taking
ownership of the hardware.
B. Architecture and Components
As shown in Figure 1, the architecture of TPM is
comprised of three high level groups: non-volatile memory,
volatile memory, and other functional units. Trust of these
hardware components, which is the foundation of TPM, is
understood based on the results noted in the Common
Criteria review of TPM [7].
Figure 1. Architecture of TPM
1) Functional Unit: TPM’s cryptographic functional unit
contains random number generator (RNG), Hash-based
message authentication code (HMAC), SHA-1 Hash, RSA
Key Generation and RSA Encryption/Decryption. The
RNG utilizes SHA-1 hash and a HMAC calculator in order
to generate good random numbers for the process and key
generation on the TPM chip. SHA-1 hashing is ideal for
small segments of data as large data sets would introduce
performance concerns. The CFU can generate a key length
up to 2048 bit RSA keys on the chip using values produced
by RNG. The RSA components perform encryption,
decryption and signatures (Safford and Zohar, 2005).
2) Non-volatile Memory: It contains an endorsement
key, a storage root key, and an owner authentication key.
The endorsement key is a randomly generated, unique RSA
public and private key pair measuring 2048 bytes. Due to
its sensitive nature, the endorsement key can be deactivated
by the purchaser or user of TPM hardware. The storage
root key is also a 2048 bit RSA key pair containing both a
private and public key and it store in the chip. Unlike the
endorsement key, the hardware manufacture does not store
any data on the storage key, as it’s populated upon taking
ownership of the hardware.
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International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 5, May 2013)
This is accomplished by Opt-In’s logic, which can be
updated on-the-fly as needed after the owner takes
possession of the device if they wish to modify the state of
a previously configured TMP option. Last, but certainly not
least, the Secure Program Execution Engine initializes the
TPM, takes hash measurements and runs program code
(TCG, 2007).
This security technique has been defeated. TPM can
provide a solution for device identity. TPM can provide
this solution because it stores the private keys and
credentials on a physical chip which makes it much less
susceptible than software based encryption techniques. This
lessens the chances of spoofing the device identity. The
usage of TPM for accurate device identity can provide a
much needed method for authenticating devices to sensitive
networks. Government agencies can leverage the TPM
capabilities today because as stated above, most enterprise
level computers and laptops already have this chip
integrated.
IV. APPLICATIONS OF TPM
TPM can be used for many security applications within
the realm of computer and network technologies.
A. BitLocker
Data protection has become an information security
issue for all types of industries such as government,
healthcare and private sector organizations. One reason
data protection is a primary security focus is because of
regulatory compliances such as the Sarbanes Oxley and
Gramm-Leach-Bliley Act. Microsoft’s BitLocker provides
full disk encryption by utilizing TPM for authorization and
decryption of hard drives. Yhe BitLocker application with
TPM is less susceptible to cryptographic key spoofing
attacks and can detect malicious activity if the keys are
being tampered with without proper authorization [2].
D. Chain of Trust
One of the main goals of information security is identity
verification of services, protocols, systems, and users etc.
System administrators rely on the best evidence possible
for the trust relationship to begin. Once a certain degree of
trust is established, then access is provided to information
system resources. As of now, many organizations utilize
credentials such as username and password for this
evidence. Because of TPM’s hardware based security
capabilities, the TPM can overcome many of these trust
issues. The TPM can be used to initiate or provide enough
reliable evidence in order to create a chain of trust because
of its reliable hardware based security techniques which
include secure credentials, secure storing of cryptographic
keys and the ability to utilize cryptographic hashes for
identity verification. There are different types of chain of
trust that can be accomplished by TPM.
B. Self-encrypting Drives (SEDs)
Organizations are starting to use self-encrypting drives
(SEDs) in order to provide the security of full encrypted
drives, but with more security capabilities. One of these
capabilities includes the IT department being able to
manage these drives via remote deactivation if a drive is
lost or stolen. SEDs are also capable of performing a phone
home function before any sensitive data can be decrypted
for viewing by the end user. Organizations that utilize
SEDs give their IT department much more access control
management of company owned data, thus gaining more
effective data protection. The capabilities of SEDs utilize
TPM’s hardware based authentication for these controls
because TPM can defend against unauthorized software
configurations from accessing the master keys for
decryption, which is a limitation of software based
encryption.
E. Virtualization
Virtualization has been a key element of information
technology, but it comes to raise the issues of security
risks. For overcoming these risks, the TPM is introduced.
Perez et al [10] successfully implemented by building the
TPM’s virtual instances. They integrated TPM software
into hypervisor environment to make TPM functions
available in virtual machines. Although the virtualization of
TPM is accomplished, a few difficulties are uncovered. For
example, certificates for securing virtualization can be hard
to virtual TPM’s instances because the chain of trust is
broken when these virtual instances are stopped or changed
to create abnormal configuration. And when virtualized
TPM instances are migrated, the chain of trust also can be
broken.
C. Device Identity
Another application that takes advantage of TPM’s
capabilities is device identity for network access. As of
now, one of the most secure ways to control device access
is to utilize restrictions based on MAC addresses.
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International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 5, May 2013)
V. FUTURE OF TPM
VI. CONCLUSIONS
The TPM can provide many capabilities and use within
computer and network security areas. Recently with the
release of Microsoft’s Windows 8 operating system, the
TPM seems to have a chance to be in the mainstream of
information security. Microsoft, a member of the Trusted
Computing Group, has provided its new operating system
which needs to utilize the embedded TPM security chip.
The adoption of TPM in Windows 8 provides advanced
malware detection and modern authentication for network
access and encryption. Windows 8 will also provide built in
support for SEDs which provide data-at-rest capabilities.
The capabilities are plentiful with an OS that natively
supports the TPM. Most of the TPM applications
mentioned in the above can be utilized with Microsoft’s
new OS.
The TPM’s abundant capabilities and enhancements will
drive further research and development. The future of TPM
seems to have a solid foundation and development. The
TPM can be used for user identification as a defense from
identity theft. A two form of factor authentication is
proposed to utilize the TPM for protecting against identity
theft. This proposal includes the use of electronic ID’s
(eID), which allows a computer user to initiate a chain of
trust utilizing a card reader. The main advantage of this
identification method is that a user can have multiple
authenticated logins to systems where as other two form
factor authentication only allows logins from one system.
With the advancement of remote and telecommuting
computing, device identification, authentication and access
control are an important factor to properly secure. The
TPM uses to create a home network that utilizes a form of
public key infrastructure. This infrastructure would consist
of hardware, software and cryptographic keys to build a
secure home network domain. This type of advanced home
network can work with ISP’s in order to create the chain of
trust in order to mitigate risks and threats within
information technology. This type of advanced home
network will be made possible with TPM security
capabilities such as malware detection, secure key
management for authentication, device and user identity
verification.
Anyway, with strong vendor adoption and expanding
research, the potential of TPM is tremendous. Continued
development of TPM is essential to ensuring integrity,
accessibility, confidentiality, and privacy among networks
and information sharing platforms into the future.
The TPM is necessary to provide more secure systems in
the Internet. This small chip provides strong protection
against malicious attacks. Business, Government and
private sector expect their systems and information to be
safe by the TPM. This is a strong motivation for putting the
TPM chip in computers and other systems.
Employing the TPM is benefit to make more secure
computing environment. Many IT software and hardware
vendors contribute to create the foundation of the TPM
which includes various trusted components, such as
symmetric and asymmetric key transfers and storage, SHA1 hashing, RSA cryptography, and a plethora of underlying
protocols. The collective efforts of each component forms
the implied trust offered by TPM, not to mention full disk
encryption, platform attestation and password protection.
The latest revision, version 1.2 or ISO/ISE standard 11889,
can be found in products offered by leading hardware
vendors, such as Hewlett Packard, Lenovo, Intel and
Toshiba.
Although the TPM provides strong security in computer
hardware and software, it does not completely preclude
from vulnerabilities. The TPM provides integrity and
confidentiality, but privacy has been a major concern as
consumers raise an eyebrow regarding hardware vendors’
ability to directly control software installations via the
TPM’s remote attestation process. This is one of the
reasons that the TPM is mostly utilized in enterprise
computing, but not yet taken off in the consumer market.
In summary, the TPM is similar to any other network
security mechanism, such as firewalls and IDPS, to provide
a single layer of security, but also the TPM can be used a
multi-faceted approach including mechanisms employed in
hardware as well as in software, policy and policy
application.
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