Microsoft details DRM for consumer devices
By Rick Merritt
EE Times
May 07, 2004 (9:30 AM EDT)
SEATTLE — Microsoft Corp. provided technical details this week of its next-generation Windows Digital Rights Management software, its first to support paid-for content on consumer electronics devices. The software will be released this summer and appear in a new class of handheld video and music players to emerge in time for Christmas.
DRM is an enabling technology for the shift to digital music and video because it provides studios a way to protect and charge for their premium content using a still-emerging variety of business models. For systems makers, the Microsoft DRM provides a new route for getting online subscription music and rental videos into portable or networked consumer devices. Creative Labs, Samsung and others will ship this fall portable media players based on Microsoft's Portable Media Center. That software includes Windows CE, a new Windows Media Player that will include the new Microsoft DRM and a new Microsoft protocol called Media Transport Protocol for fast data transfers over USB 2.0. The devices come with a 320 x 240 LCD and are generally based on an XScale PXA255 processor.
The systems will compete with a handheld version of the Playstation that Sony Corp is expected to launch next week (May 9). The Sony system, billed by some observers as the next-generation Walkman, will play videogames in addition to video and music.
With the new Microsoft DRM, code-named Janus, Web-connected consumer devices including handheld gear and networked set-top boxes can buy content directly over the Internet without going through a PC. The DRM will also let PCs transfer or stream to consumer devices music and videos from online subscription and rental services originally purchased on the PC. Previously, Microsoft's DRM only worked on PCs.
The new DRM only works with content encoded in Microsoft's Advanced Systems Format (ASF), a container used primarily by its Windows Media format and codec. A small group of cellphone makers in Japan have used ASF. However, the DRM does not support content encoded in other popular digital media formats including those used by Apple Computer and Sony.
"Supporting other formats was not a priority for us at this point. We wanted to get this right in ASF," said Brooks Cutter, lead program manager for Windows Media DRM. The DRM uses a secure time stamp from an onboard real-time clock and links to a system-specific ID or serial number to track when a song or movie from a rental or subscription service has expired. Portable devices will be required to prevent users from tampering with the system clock. They may have to initialize the device clocks over the Internet as a security measure.
Systems makers also will be held responsible for providing secure systems buses and storage of digital keys. That includes not allowing users to transmit paid-for content via unapproved I/O links under some scenarios.
In tandem with the new DRM, Microsoft has designed a so-called Media Transport Protocol for USB 2.0 geared for quickly transferring large object files securely between a PC and a consumer device. MTP is optimized for use with the Janus DRM and will first appear in Microsoft's Portable Media Center software this fall.
Microsoft also hopes MTP will be used on future digital still and video cameras, and eventually on PDAs and cellphones. MTP is a superset of Picture Transport Protocol widely used on digital cameras today.
Microsoft is making the Janus DRM available as C language source code that can be ported to most processors. Chip makers Cirrus Logic, PortalPlayer, Sigmatel and Texas Instruments are porting the new DRM software to their processors used in MP3 players, said Cutter. They will likely optimize the source code by putting key sections into assembly language.
The DRM uses a set of encrypted digital keys to transfer licenses and policies securely between devices. Currently it employs on portable devices the so-called "cocktail" algorithm of 56-bit DES and 64-bit RC4 along with 160-bit Public Key Infrastructure (PKI) for storing keys. Networked devices such as set-tops use 128-bit AES and 2,048-bit PKI cryptography.
Future portable versions will migrate to AES, said Cutter. That could encourage chip makers to support AES directly in future consumer silicon. Both portable and networked devices use SHA-1 hashing algorithms.
The DRM requires about 194 kbytes of ROM for program storage and 37 kbytes of RAM for working space. It is running in Microsoft's labs on relatively low-end ARM 7 and TI 55x-class DSPs, said Cutter.
The DRM is available for a one-time licensing fee of $25,000 plus a per-unit royalty to be negotiated with Microsoft. Currently Microsoft is licensing MTP free of charge.
