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Electronic Design

Digital Rights Management: The Future Is Secure Hardware

The recent explosion of digital music on the Internet has transformed digital rights management (DRM) from an esoteric technology into a hot topic for all content providers. Major record labels stand at the front of the DRM wave, but, electronic book and traditional publishers, video producers, and software developers are right behind them. DRM is making its initial appearance in the PC world while spreading quickly to appliances. Almost all owners of valuable digital content are concerned with rights management.

DRM systems grant owners of digital content the ability to specify rules for that content. The rules could be simple like in a first-generation client-server system for downloading music. The rule may be "pay $1.00 by credit card to download this song." In other systems, such as ours, rules are more sophisticated. Examples include supporting pay-per-use, affinity groups, and volume discounts. The protection is persistent. Content isn't just downloaded to a file, It's kept in a special encrypted container like an InterTrust DigiBox, where the rules are followed each time it's used.

Persistent protection is only practical when it occurs in the user's computer or appliance. This requires a secure computer. Highly advanced tamper resistant software, similar to our InterRights Point product, create a safe environments within the PC platform. But any software-only solution can be attacked relatively easily due to the PC's open architecture. Software can be perfectly replicated at zero cost and be analyzed by only the computer it runs on. If one attempt fails, the attacker can start over. Secure hardware solves this problem.

The analysis of hardware requires specialized tools and skills. Developing perfect duplicates of hardware components is nearly impossible. Unlike software, hardware has the ability to actively detect and respond to attacks.

A secure hardware device combines processing, memory, and I/O capabilities in one VLSI package. When it's first powered on, it runs a protected bootloader in internal memory. By loading cryptographically protected external data, it establishes a secure environment for DRM functions and other activities, such as the user interface, a file system, and the audio processing in a portable music player. Security kernel techniques prevent these activities from interfering with the DRM and security functions. As long as all protection-critical functions operate only in internal memory, the system is highly secure.

In addition to logical protection, physical protection is important. Through differential power analysis and timing analysis, an attacker observes device operation and deduces secrets hidden inside. Fault injection might be carried out, where external power and clock signals are manipulated. Processing glitches can also be executed to reveal secret information. Reverse engineering can determine how a device works. Countering reverse engineering may be accomplished with continuously powered tamper-detection circuitry. Any secrets inside are erased instantly when power is interrupted.

Physical protection counter measures have been largely limited to smart cards and special-purpose government systems. Still, they also can be applied to general-purpose devices at low cost.

In partnership with Cirrus Logic, ARM Ltd., and others, InterTrust is defining secure hardware devices for a wide variety of applications. Initially, we'll focus on logic protection for near-term applications. But the future is clear. DRM is important. It will be provided by secure systems using a full range of hardware protection methods.

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