How Vista Lets Microsoft Lock Users In

How Vista Lets Microsoft Lock Users In
How Vista Lets Microsoft Lock Users In 

By Cory Doctorow
Dec 5, 2006

What if you could rig it so that competing with your flagship product 
was against the law? Under 1998's Digital Millennium Copyright Act, 
breaking an anti-copying system is illegal, even if you're breaking it 
for a legal reason. For example, it's against the law to compete head-on 
with the iPod by making a device that plays Apple's proprietary music, 
or by making an iPod add-on that plays your own proprietary music. Nice 
deal for Apple.

Microsoft gets the same deal, courtesy of something called "Information 
Rights Management," a use-restriction system for Office files, such as 
Word documents, PowerPoint presentations, and Excel spreadsheets.

We've had access control for documents for years, through traditional 
cryptography. Using PGP or a similar product, you can encrypt your files 
so that only people who have the keys can read them.

But Information Rights Management (IRM), first introduced in Office 
2003, goes further -- it doesn't just control who can open the document, 
it also controls what they can do with it afterwards. Crypto is like an 
ATM that only lets you get money after you authenticate yourself with 
your card and PIN. IRM is like some kind of nefarious goon hired by the 
bank to follow you around after you get your money out, controlling how 
you spend it.

With IRM, an Office user can specify whether her documents can be 
printed, saved, edited, forwarded -- she can even revoke access to the 
documents after sending them out, blocking leaks after they occur. 
Documents travel with XML expressions explaining how they can and can't 
be used.

Now, if anyone was allowed to make a document reader, it would be simple 
to make a reader that ignores the rules. This is a perennial problem for 
Adobe's password-restricted PDFs -- the only thing that distinguishes 
them from normal PDFs is a bit that says, "I am a restricted PDF." Just 
make a PDF reader that ignores the bit and you've defeated the 
"security." It's about as secure as one of those bogus "Confidentiality 
notices" that your mail-server pastes in at the bottom of every email 
you send.

There are plenty of readers for Microsoft's Office formats these days. 
Apple makes at least two -- Pages and TextEditor. Google and RIM both 
have Office readers they use to convert Office documents to other 
formats. And there's also free readers like, which are 
open source and so can be modified by anyone with the interest to write 
or commission new code for them.

But now that the format is well understood, Microsoft needs another way 
to ensure that it only hands keys out to readers that can be trusted to 
follow the rules that accompany them. Pages or can 
request a set of document keys just as readily as Office can. Microsoft 
can try to create secret handshakes to make sure it only gives out the 
keys to authorized parties, but just as the document format can be 
cracked, so can the handshaking.

IRM has an answer. Unlike a crippled PDF, a restricted Word file is 
encrypted. Only authorized readers will get the keys. This technology 
will return Office users to the days before the file format had been 
reverse-engineered by competing products like WordPerfect, where reading 
an Office file meant licensing the file-format from Microsoft.

If anyone makes a client that listens to its owner instead of Microsoft, 
then the system collapses. No-print, no-forward, revoke and other flags 
for the document can simply be ignored. Once Microsoft sends a 
decryption key to an untrusted party, all bets are off -- Microsoft 
loses its lock-in and you lose any notional security benefits from IRM. 
This has been a purely theoretical problem until recently -- but the 
advent of Vista and Trusted Computing should put it front-and-square on 
your radar.

Microsoft has an industrial-strength answer to the problem of figuring 
out whether a remote client is authorized to request keys. Trusted 
Computing. For years now, most PC manufacturers have been shipping 
machines with an inactive "Trusted Computing Module" on the motherboard. 
These modules can be used to sign the BIOS, bootloader, operating 
system, and application, producing an "attestation" about the precise 
configuration of a PC. If your PC doesn't pass muster -- because you're 
running a third-party document reader, or a modified OS, or an OS inside 
a virtual machine -- then you don't get any keys.

What this means is that Apple can make Pages, Google can make its 
Doc-converter, and can make its interoperable products, 
but none of these will be able to get the keys necessary to read 
"protected" documents unless they're on the white-list of "trusted" 

What's more, adding crypto to the mix takes us into another realm: the 
realm of copyright law. The same copyright law that prohibits competing 
head on with Apple also prohibits competing head-on with IRM. EDI and 
other middleware companies built their fortunes on writing software that 
unlocks your data from Vendor A's format so you can use it with Vendor 
B's product. But once Vendor A's data-store is encrypted, you run afoul 
of the law merely by figuring out how to read it without permission.

Vista is the first operating system to begin to use the features of the 
Trusted Computing Module, though for now, Microsoft is eschewing the use 
of "Remote Attestation" where software is verified over a network 
(they've made no promise about doing this forever, of course). No 
company has spent more time and money on preventing its competitors from 
reading its documents: remember the fight at the Massachusetts 
state-house over the proposal to require that government documents be 
kept in open file-formats?

The deck is stacked against open file formats. Risk-averse enterprises 
love the idea of revocable documents -- HIPPA compliance, for example, 
is made infinitely simpler if any health record that leaks out of the 
hospital can simply have its "read privileges" revoked. This won't keep 
patients safer. As Don Marti says, "Bill Gates pitch[ed] DRM using the 
example of an HIV test result, which is literally one bit of 
information. If you hired someone untrustworthy enough to leak that but 
unable to remember it, you don't need DRM, you need to fix your hiring 
process." But it will go a long way towards satisfying picky compliance 
officers. Look for mail-server advertising that implies that unless you 
buy some fancy product that auto-converts plain Office documents to 
"revocable" ones, you're being negligent.

No one ever opts for "less security." Naive users will pull the 
"security" slider in Office all the way over the right. It's an 
attractive nuisance, begging to be abused.

The Trusted Computing Module has sat silently on the motherboard for 
years now. Adding Vista and IRM to it is takes it from egg to larva, and 
turning on remote attestation in a year or two, once everyone is on 
next-generation Office, will bring the larva to adulthood, complete with 
venomous stinger.


Cory Doctorow is co-editor of the Boing Boing blog, as well as a 
journalist, Internet activist, and science-fiction writer.

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