Group Releases Spec for Cellphone Security

SAN JOSE, Calif. — The Trusted Computing Group (TCG) officially rolls out its standard for cellphone security Wednesday (Sept. 13), a specification three years in the making. The spec is intended to help make it easier to protect mobile data and applications, although several hurdles lay ahead for broadly adopting it.

Nearly 50 companies helped define the Mobile Trusted Module (MTM) spec to be posted and available free of charge starting September 13 at the TCG Web site. However, two of the largest cellphone chip makers—Texas Instruments and Qualcomm—did not participate in developing the spec. Indeed, the only carriers involved in the work were from Europe: Vodaphone and France Telecom.

The PC-oriented TCG kicked off the cellphone effort in 2003 and spent much of the first year recruiting stakeholders from the mobile world. The group coalesced in 2004 when it spent most of the year hammering out applications. Last year, its focus was on how to extend the group's PC security spec to the cellphone environment with its multiple stakeholders including users, carriers, OEMs and content providers.

To support those different parties, the MTM spec allows multiple roots of trust. A root of trust is a key or certificate typically expressed as a number that can only be obtained by a calculaiton using information private to a system or user. Local roots of trust can support multiple users of a single handset. Remote roots of trust can allow a carrier, OEM or application provider to prove they are trusted enough to modify or "reimage" the handset's operating system or other key software.

Like the existing PC spec, the MTM can use protected memory to store digital keys, certificates and passwords and support integrity checks of the device to measure its health and whether its state has changed.Those tasks are handled with the same underlying RSA key cryptography for verifying digital certificates and the SHA-1 hashing algorithm employed by the existing PC spec. However, the spec uses those techniques differently to support multiple roots of trust locally and remotely.

Separately, the TCG is evaluating plans to migrate to the SHA-256 algorithm in light of cracks that have shown SHA-1 was more vulnerable than previously thought.

The spec allows for any sort of compliant implementation that supports its basic commands and control structures. Today, many chip sets already support RSA and SHA-1 for local security. That means they might only need to update their software to comply with the spec, said Mark Redman, a principal staff engineer in security for Freescale Semiconductor who worked on the spec.

"The standard is targeted at being design neutral," Redman said. "For many people that work will be more software intensive," he added.

Sometime in 2007, the group plans to release a broader platform security architecture showing carriers and application developers how the MTM can be employed. In parallel, the TCG is developing protection profiles for the cellphone it hopes will be ratified as part of the Common Criteria in 2007.TCG said the new spec works with existing cellphone security schemes that use SIM and UICC cards. It also co-exists with separate security specs published by groups including 3GPP, Open Mobile Alliance, Open Mobile Terminal Platform and the Mobile Industry Processor Interface Alliance.

"The [TCG] member companies, which include handset makers, service providers, silicon makers and others, have worked closely to create an open specification that provides a high level of security and trust for the mobile phone and that can be widely deployed industry-wide, Janne Uusilehto, chairman of TCG's Mobile Phone Work Group and Nokia's head of product security, said in a statement.

TCG's mobile working group also includes representatives from Agere Systems, ARM, Atmel, Broadcom, Ericsson, Hewlett Packard, IBM, Infineon, Intel, Microsoft, Motorola, Nortel, Philips, Renesas Technology, Seagate Technology, Sony and STMicroelectronics.

According to a market research survey of 503 mobile workers employed in large U.S. companies, the cellphone is by far the most common wireless device used by businesses. It is used more than twice as widely as laptops with Wi-Fi or other Internet connections. Users identified authentication, encryption and secure data transmission to corporate networks as their top mobile security issues.