Trusted Platform Modules and their encryption capabilities enhance operations on and off the field.
BY Donald Palmer
Information sharing is at the heart of a new military field operations culture. The days of tactical information traveling in a straight line from one source to another are gone. Today's multidimensional battlefield, enhanced by the latest advances in computer technology, can incorporate many other elements besides warfighters and their chain of command. Now there are coalitions, nongovernmental organizations, and communities of interest possibly all involved in the same operation.
This interplay of resources and capabilities demands incredible accuracy and security of information. In fact, the success of strategic operations can rest absolutely on the ability to trust the information that one source receives from another. Keeping that information secure is essential, even if it resides in a damaged vehicle.
The consequences of relying on a computer that cannot be trusted are dire. Imagine if your computer data was visible to others, or worse, could be changed by others. What if you are part of a sensitive military operation and crashes, viruses, and spyware were involved?
These concerns have given rise to an emphasis on "trusted computing." When you flip a light switch, you trust the lights will come on. Likewise, turn on your computer, and you trust it will behave as always, and nothing has been modified or stolen from it.
To determine if a computer can be trusted, the industry suggests asking these questions:
- Did a trusted system boot the computer?
- Is that system still running on the computer?
- Is the running system approved for the application?
- Can the system join a trusted network?
- Can the system have access to trusted network service?
Gathering evidence is the only way to prove that a computer system has not been modified. Once the evidence has been gathered and trust has been established, each of the questions above can be answered. To do this, a baseline must be established. By comparing a baseline measurement against the measurement taken every time the computer is powered on, the decision of trust becomes an evaluation of the evidence.
Measuring a computer involves the types of devices that make up the computer system: the keyboard, processor, memory, data storage, and so on. Once you have all the configuration data, it can be encrypted. The encrypted data and the encryption key are stored (separately, of course) where no one else can find them, so they are virtually tamperproof. This provides a safe measurement of the computer's hardware that can be used as evidence to prove the computer can be trusted.
Computer operators, especially in the military, must be able to trust the software, as well. As with hardware, the goal is to measure the software on the computer, encrypt it, and store the data where it is safe.
Concerned with security issues, a group of the largest companies in the computing industry, including Intel, Microsoft, HP, IBM, and others, formed a not-for-profit organization called the Trusted Computing Group (TCG) in 2003 to develop, define, and promote industry standards for trusted computing.
Since that time, the TCG has defined several specifications, and two of the most important are the Trusted Platform Module (TPM) and the Trusted Software Stack (TSS). Together, TPM and TSS form a new level of security.
Trusted Platform Module
TPM generates cryptographic security keys, encrypts data streams and creates wrapping keys, as well as provides secure storage for self-generated and other keys.
The cryptographic processor includes an interface to the host computer system through a secure I/O bus. The TPM processes commands and data from the host system; required responses are relayed back to the host computer system through this bus.
The cryptographic processor generates encryption keys to encrypt data streams. For added security and independent operations, the TPM has a built-in random number generator and encryption engine. The key generation uses an RSA generation algorithm and the SHA-1 encryption hashing function.
Data in persistent storage only can be accessed through the encrypted Storage Root Key, which is required to open up the block for use by application software. Among the primary keys are the Endorsement Key (EK) that is "burned" into the storage during manufacturing. The Storage Root Key (SRK) embedded in the TPM security hardware to protect TPM keys created by applications, so that these keys cannot be used without the TPM; and the Platform Configuration Register (PCR) to store the evidence gathered about the computer's configuration.
Versatile storage stores keys generated by the TPM or by others. The Attestation Keys are generated to secure platform configuration. There is also a generic key storage area that is used to store keys from a multitude of sources.
Simply keeping a computer secure is not enough. You have to know you are connected to a secure network and that the network will trust your computer. In a TPM-enabled system, secure operation begins once the hardware configuration evidence is stored in the PCR for safekeeping. Each time the platform is booted, the BIOS evaluates the evidence to determine if the hardware can be trusted. This provides the operating system and associated applications with a "root of trust."
Once evidence is gathered, a computer essentially presents it to the server, which decides to allow the computer to access one or more of the trusted networks. The TPM assists with the presentation of this evidence. The Attestation Key encrypts the evidence presented such that only the server can view it, and the evidence is tamperproof.
Establishing a root of trust when a computer is powering on is the first step. Because most system attacks occur while a computer is running, a run-time root of trust must also be established by periodically refreshing, re-evaluating and representing the evidence. Using the run-time root of trust will detect many system attacks.
Users and manufacturers recognize the urgent need for improved computing security, and the TPM is fast becoming a standard, especially in military applications. The U.S. Army and the Department of Defense have mandated that every new small PC they purchase comes with a TPM.
According to the TCG, TPMs have been shipped in more than 100 million enterprise-class computers. It has been reported that Intel, AMD, and Dell will continue to include TPMs in upcoming generations of hardware, and Microsoft will include trusted computing in its new operating systems.
Donald Palmer is chief technology officer of embedded computing specialist General Micro Systems Inc. in Rancho Cucamonga, Calif.