14 MA XIMUMPC NOVEMBER 2004
Deciphering
Digital Rights
Management
Like it or not, DRM impacts
all of our lives. Maximum PC
investigates how the 5 most
popular DRM schemes work—
and the problems they causeQuickStart
The beginning of the magazine,
where articles are smallDigital rights management is becoming
an inextricable part of PC users’ lives.
It’s up to you to know what you can
and can’t do with today’s DRM.E
ven the mighty lobbies of the enter-
tainment and software industries are
no match for the popularity of broad-
band and the resilience of peer-to-peer net-
works. With this in mind, we expect to see
more digital rights management, or DRM,
incorporated into everything from online
music purchases to store-bought games
to hardware gadgets and other playback
devices. In this first overview of applied
DRM, Maximum PC unveils the mechanics
behind today’s digital rent-a-cops—and the
problems they’re most likely to cause.iTunes won’t let me play tracks
that I haven’t acquired licenses
for—but I bought them!
PERPETRATOR: FAIRPLAY
If you’ve “installed” licenses on more
than three PCs, or if you recently
performed a clean installation of
Windows and are trying to play iTunes
tracks, FairPlay steps in and says: “Oh
no you don’t.” That’s because every
time you buy a FairPlay-encrypted MP
track, a random user key is generated
and stored on Apple’s servers and in
your iTunes database. This key is used
by iTunes to receive and decrypt the
master key (which is retrieved from
Apple’s servers) necessary to play the
embedded AAC file. Apple’s servers willauthorize up to three PCs to receive their
own unique user key. After that, further
requests are refused unless one of your
PCs is de-authorized, thereby revoking
its user key.
WARNING: No other portable player
besides Apple’s own iPod is authorized to
play FairPlay-protected content.I copy DVD-Video files to my
laptop’s hard drive!
PERPETRATOR: CSS
That’s because the files, including crucial
data headers, are encrypted. In order to
decrypt them, your DVD-ROM and your
hardware or software player have to prove
to each other that they’re licensed to access
the files. They do this by generating a
random number and then encrypting this
number by using a secret mathematical
formula that converts the number into
an 80-bit string (or “hash”). The DVD-
ROM and the player hardware/software
exchange these values over the system
bus, and if both return values that agree
with the formula, then the player—again,
hardware or software—uses a player key
(assigned from a master list of 409 keys)
to unlock a disc key on the DVD itself.
The disc key, in turn, allows the player to
retrieve the rest of the keys that unlock
the disc’s contents. If you try to simply
copy the files, they remain encrypted and
irretrievable because your PC has none of
the keys required to unlock, or even locate,
most of the content.
WARNING: Using decryption tools such
as AnyDVD or DVDDecrypter is illegal under
the Digital Millennium Copyright Act.I can’t play purchased WMAs
on my favorite media player!
PERPETRATOR: WINDOWS MEDIA DRM
Windows Media DRM works pretty much
just like Apple’s FairPlay. Centralized
servers dish out “licenses” and keep track
of which PCs are authorized to play
protected media. One of the nice things
about Windows Media DRM, as opposed
to FairPlay, is that Microsoft is willing to
license the technology to other companies
so you don’t have to use Windows Media
Player to listen to your music or transfer
your tracks to a portable device. However,
it’s important that you be certain your
portable player supports Windows Media
DRM before you purchase protected WMAs.
WARNING: Because Windows Media
DRM licensing allows retailers to set their
own usage policies, usage permissions
may differ from one site to another, and
individual song permissions can vary
within the same site!I can’t play a purchased CD on
my PC!
PERPETRATOR: KEY2AUDIO
Key2Audio is Sony’s proprietary copy
protection technology, and works by
inserting a track onto the disc which, in
effect, confuses PCs with a bogus table
of contents. It became something of a
laughingstock, however, when it was
revealed the technology could be defeated
by using a black Sharpie pen to outline the
outer edge of a protected CD, effectively
wiping out the area where the bogus
track is stored. Although used mostly on
European music CDs, this form of audio
CD protection is creeping into the U.S.