- Introduction
- Why Are Trusted Platforms Being Developed?
- The Trusted Computing Platform Alliance and the TCPA Specification
- What Is a Trusted Platform?
- Basic Concepts in the Trusted Platform Model
- Basic Functionalities of a Trusted Platform
- Benefits of Using Trusted Computing Technology
- Summary of TCPA Technology
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Benefits of Using Trusted Computing Technology
Both companies and consumers receive commercial benefits from Trusted Platforms. In this section, we briefly discuss the following:
Benefits of using Trusted Platforms that will emerge in the short, medium, and long term
How Trusted Platforms encourage greater customer confidence
How Trusted Platforms encourage e-business and enhanced e-services
Benefits to the User
Probably the most important aspect for users is that Trusted Platforms provide a low-cost way to trust a software environment for some particular purpose.
A TP allows users to answer the following questions (see Figure 5):
Am I appropriately authorized? (platform authentication)
How can I have confidence that my computing platform will behave in the way I expect? (integrity)
How can I trust a remote system that's not under my control? (integrity)
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Figure 5 Questions addressed by Trusted Platforms.
In addition, a TP supports any means of user authentication. Therefore, it can support the continuing personalization of web sites and user mobility, such as VPN and hot-desking.
The Trusted Platform architecture is designed to provide immediate, medium-term, and long-term benefits to users. Longer-term benefits are predicated on software improvements: All TPM chips support all TCPA functions, but existing software applications are not designed to take advantage of them. When TCPA platforms are more common, it's anticipated that customers and Internet service vendors (ISVs) will start developing applications that use these more advanced functions. The most advanced functions require a public key infrastructure (PKI) and are designed for use by e-services.
Short-Term (Immediate) Benefits
In the short-term, benefits of Trusted Platforms are likely to be based on "protected storage" functions. Customers can use protected storage to protect the confidentiality of data on their hard disks in a way that's fundamentally more secure than pure software solutions. You'll need a basic TCPA implementation with a TPM chip embedded within a platform and associated software provided by the TCPA chip manufacturer.
In providing protected storage, the TPM does the following:
Acts as a portal to encrypted data
Provides an option (which doesn't have to be used) such that encrypted data can then be decrypted only on the same platform that encrypted it
Provides for digital signature keys to be protected and used by the TPM
Medium-Term (Intermediate) Benefits
In the medium term, benefits of Trusted Platforms will probably also involve the measurement of integrity metrics relating to the software environment on the platform, for use by the platform. This scenario is the same as the short-term solution, but it requires additional software. Customers can then protect their sensitive data against hacker scripts, by automatically preventing access to data if unauthorized programs are executed.
The specific mechanism has the following properties:
It uses the TPM chip.
It acts as a portal to encrypted data, such that this data can be decrypted only if the platform has a given set of software environment integrity metrics. If a hacker loads a script, the presence of that script changes the state of the software environment and the TPM denies access to any secrets that were linked to that previous software environment. The script still executes, but it can't access any such secrets and can't interpret any information protected by such secrets.
This feature can be exploited through software at different levels in the software stack, ranging from stand-alone applications to a fully TCPA-aware operating system (OS).
Long-Term Benefits
Longer-term benefits of Trusted Platforms involve the reporting of integrity metrics relating to the software environment on the platform, for use by third parties. This benefits e-business. The scenario requires additional public key infrastructure (PKI) support, whether restricted to a corporation or extended across organizational boundaries.
Users and their partners, suppliers, or customers can connect their IT systems and expose only the data that's intended to be exposed.
The specific mechanism has this feature:
TCPA provides reporting of integrity metrics of the software environment on a specific platform. This allows a remote party to verify the software environment in a TCPA platform before sending data to that platform. This provides confidence in the software state and identity of a remote party, enabling higher levels of trust when interacting with this party.
Both trusted clients and trusted servers can use this feature.
How Trusted Platforms Create Better Customer Confidence
Trusted Platforms can help create better customer confidence in several ways, including the following:
Enhanced security using hardware
Feedback about trust to the user
A technological foundation for privacy
Trustworthy digital signature
Hardware-Based Security
Processes that execute on specialist security hardware are better protected than processes that execute on ordinary computing engines. These protected functions are much more resistant to interference and snooping from logical or physical attack, so there is greater confidence in those processes than in processes that execute on an ordinary computing engine.
In a conventional platform with a conventional crypto co-processor, the co-processor protects all its functions from logical and physical attack but doesn't protect processing on the ordinary CPU. A Trusted Platform provides logical and physical protection for secrets and logical protection for the data protected by those secrets (which is processed on one of the main CPUs). The TPM acts as a conventional co-processor for secrets, and the integrity mechanisms prevent the release of secrets to inappropriate processing environments and permit a local or remote user or computer to verify the trustworthiness of a platform before interacting with that platform. So a Trusted Platform protects a larger number of processes than a conventional platform with a conventional crypto co-processor: A critical few processes—dealing with secrets—are protected by a minimalist crypto co-processor. Other processes on data that uses secrets are less protected than they would be inside a crypto co-processor. This is because no physical protection exists, for example, against deletion. But they're better protected than ordinary processes outside a crypto co-processor because the confidentiality and integrity of the data are protected.
Specifically, a Trusted Platform provides hardware protection for keys and other secrets, which would normally be used to encrypt files or gain access to servers or other networks. The TPM prevents the release of secrets until presentation of an authorization value and/or the presence of a particular TPM and/or the presence of a particular software state in the platform. The TPM prevents inappropriate access to encrypted files and network resources by, for example, snooping around a hard disk, moving a hard disk to another platform, or loading software to snoop on other processes.
Provision of Feedback about Trust to the User
By interacting with Trusted Platforms using smart cards or handheld computers such as personal digital assistants (PDAs), a user can decide whether to trust a computer or computing infrastructure.
A smart card or other handheld computer can be programmed to interrogate a Trusted Platform (local or remote), retrieve identity information and integrity metrics, and compare the identity and integrity metrics with expected values. If they differ, the smart card or handheld computer user can refuse to interact with the Trusted Platform because it's the wrong computer or because it's in an inappropriate software state and not to be trusted for the intended purpose.
This enables a user to access an arbitrary computer platform in an organization or public area, or an arbitrary server, and to determine whether it can be trusted to work on private information and not reveal the private information without authorization from the user.
Provision of a Technological Foundation for Privacy
Both businesses and individuals are increasingly concerned with the privacy of their confidential and personal information, particularly when their computer platforms are connected to networks.
In the computing context, privacy provides a way to prevent others from gaining access to information without the informed consent of its owners. Cell phones, telephone caller ID, credit cards, and the Internet provide people with a dramatic new level of freedoms that can enhance business processes and personal lives, but these innovations come with privacy concerns. All of these systems are capable of providing information, including financial and personal data that most users assume to be private. The TCPA believes that the ability to ensure such privacy is an essential prerequisite of a trusted system. This privacy needs to be as robust as any other aspect of the trust in the system. [TCPA white paper, "TCPA Security and Internet Business: Vital Issues for IT," August 2000]
Privacy controls should determine whether it's permissible to reveal that the information exists and the circumstances in which the information can be disclosed or used. A credit card number is not secret, for example, but it is private. Only the owner of a credit card has the right to use the credit card number. Others who have been given the credit card number should not disclose, distribute, or use the number in a manner that's not approved by the card owner. It follows that data is rendered private if the owner of the data can control distribution of information about the data, or even knowledge of the existence of that data. Whether particular data should be treated as private data depends on the nature of the data and the opinion of the owner of that data. Some people are not concerned about privacy, and others are. One person may consider that a particular type of data must be private, while another may not.
Any data, even secret data, can have a privacy attribute. Some data associated with Trusted Platforms doesn't require security protection but could be considered privacy-sensitive by some users. The best such examples are public asymmetric keys (such as the public Endorsement key) and X.509 certificates (such as the Endorsement Certificate and identity certificates). To maintain the privacy of such data, the TCPA specification requires that access to such data be under the control of the owner of that data. An owner who's not concerned about privacy can distribute the data or publish its existence to his heart's content. An owner who is concerned about privacy should use whatever mechanisms are provided to prevent others from accessing the data or learning about the data.
TCPA provides a novel form of privacy protection by preventing the revelation of secrets unless the software state of a platform is in an approved state. If secrets are kept on a server built on a Trusted Platform, a user can verify that the server is the expected platform and is operating as expected even before sending private information to the server. After a user's private information is on a server, the user can be reassured that data in the server will become unavailable if the software environment on the server changes (during a hacker attack, for example). Thus, the secret should never be used in unapproved circumstances.
Some aspects of privacy are expressed in Trusted Platforms through explicit commands or special features of commands or protocols. These commands or enhancements enable the TPM owner to dictate some aspect of a TPM's behavior, such as whether it will do "real work" and whether it will accept an owner. For example, the entire notion of TPM identities exists only to provide privacy when a TPM owner uses a signing key that identifies his platform. A user has multiple trusted attestation identities that are associated with a TPM, which is particularly useful in e-business because different identities can be associated with different types of tasks. The technology prevents someone from building up a profile of the user by combining behavior associated with different identities. A user can use one identity when dealing with a bank, another identity when buying goods, and yet another identity when posting opinions to a newsgroup. An identity can have any arbitrary name or label (even the user's real name, if he or she wishes), yet each identity can prove that it corresponds to a Trusted Platform. A third party can still track the consistency of a user's behavior and benefit from being able to inspect the environment on the associated platform to see if it's trustworthy, but the third party can't correlate activities performed using different identities. (Or, at least, exploiting TCPA mechanisms cannot enable such a correlation.)
TCPA also respects the privacy of a user of a Trusted Platform. TCPA differentiates between the user of a Trusted Platform and the owner of a Trusted Platform. The owner has certain privileges over a TP, but a user's data is private; even the owner of the platform can't access that data without permission from the user. Hence, a platform could be owned and used by a single owner or user (in the case of a consumer or small business), or owned by one entity and used by another entity. This would be the case in a corporate environment, where the IT department is the owner, and the user is the individual to whom the platform has been issued.
Provision of Trustworthy Digital Signatures
Digital signatures will become more important as they gain greater legal status, and Trusted Platforms can support and enhance the use of digital signatures. Users realize these benefits in the following ways:
A Trusted Platform protects signature keys using the TPM, never reveals those keys outside the TPM, and uses such keys to digitally sign data submitted to the TPM.
A Trusted Platform can enhance digital signatures by incorporating integrity metrics that indicate the software state of the platform when data is signed.
Depending on the implementation of the TPM, a Trusted Platform can further enhance signatures to guarantee that what is signed corresponds to what was seen by the signer.
Benefits to Business
The higher levels of trust that are enabled by Trusted Platforms are valuable to businesses for the following reasons:
Companies gain by being trustworthy.
Brand image suffers if there is a breach of trust or privacy.
Better trust enables more powerful management services.
Consumers' trust is an important business enabler.
Improved trust and security are necessary to the delivery of business-critical e-services.