Transcript Diapositiva 1 - uni

Windows Media Rights
Manager
and
FairPlay
Seminar Digital Rights
Management
Clara Fernández de Castro
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Introduction
• Piracy of copyrighted entertainment is
not new -> cassette tapes.
• Digital multimedia files can be easily
copied and distributed without loosing
quality.
• The efficient implementation of a DRM
system grants a maximum and wide
distribution of audio and video to
consumers.
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Windows Media Rights
Manager
• Windows Media Rights Manager Flow
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–
–
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Encrypting Content
Sharing Business Rules
Challenge and Response
License Delivery
• Attacks against WMRM
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Key points of the process
• Enables content owners to protect digital
media (Encrypt content).
• User must have the corresponding license to
play the content (Request License).
• License is issued by a third-party license
provider (Create license).
• License "unlocks" the content and determines
how the content can be used (Unlock
content).
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Encrypting Content
• Hardware requirements: Windows 2000 server and
WMRM SDK.
• Account set up with the license provider.
• Content Packager uses web-based interface to
handle the encrypting process
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Packaged Windows Media File
 The seed along with the key ID are used to generate the key:
Seed + Key ID = Key
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Steps to complete the package
•
•
•
Generate or specify a key using the key ID and the
license key seed.
Generate and sign the content header using private
signing key.
Encrypt the file using this information.
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Sharing Business Rules
• Key benefit from WMRM: flexibility in supporting different
business models, such us:
–
–
–
–
Purchase
Pay-per-view
Free trial version
Limited play
• Content owner and license issuer share some “secrets”
• Secrets:
– Seed
– Public key
– Business rules
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Example: sharing secrets
•
•
The content owner defines two different schemes:
Audio File -> available on a subscription basis
Video File -> “try before you buy” promotional
version
License issuer must update database.
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Redirecting user to a purchase site
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License issuer database
•
•
Content owner is able to define multiple business
rules for the same piece of content.
License issuer uses the key ID and an attribute
containing the corresponding business model to
maintain his database.
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Challenge and Response
• Process starts when a consumer attempts
to play a protected piece of content.
• For playing the content, he or she must
acquire a valid license.
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Example
- Encrypted key used to encrypt the content.
- Specific rights.
- Information about Bob’s computer.
- The certificate of the license issuer.
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License Delivery
• Four examples of how consumers acquire licenses:
1) non-silently
2) silently
3) non-pre-delivered
4) pre-delivered
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Non-silent License
The consumer is prompted to perform some
tasks before receiving a license
Bob visits an online Music Store that he is subscribed to.
The site contains the newest song he has been looking
for. The site offers a free promotion of this song in
exchange of some information about Bob, such us his
email address, name, age and nationality. If Bob agrees to
share that demographic information about him, he would
be able to receive and play the song.
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Silent License
There is not user interaction required.
Bob once again visits the Music Store, but this time he
clicks a song which is included in his subscription service.
The song is downloaded in his computer and the license
is acquired without extra task to play the song.
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Non-pre-delivered license
The license is acquired separately and after the content is acquired.
Bob sends his friend Alice the first song he downloaded.
Alice receives the file by email, but the license that will
allow her to play the song it is not included in the content.
When Alice clicks on the song to play it, she is asked to
enter some demographic information about herself before
she is able to play the song.
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Pre-delivered license
The license is delivered before or at the same time as the content.
Bob wants to rent a movie on the Web. In this case, Bob
must purchase the movie before a valid license is
delivered in order to play the content. After entering his
credit card number and more information to pay the
license, he is able to play the movie. This procedure
allows content owners to promote and monitorize their
content.
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Attacks against WMRM
Not properly cracked, but attacked in
two different ways:
1)
Remove DRM from .wmv files.
- Freeme.exe
2) Ads and adware
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Freeme.exe
•
October 2001, Microsoft confirmed the software
“freeme.exe” could strip off the protections that prevent
a song from being copied an unlimited amount of
times.
•
The software from "Beale Screamer" essentially used
information found in this license to fool the DRM
software, stripping off the protective technology
entirely.
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Freeme.exe
•
Microsoft quickly reacted delivering new versions of the Windows
Media Rights Manager and giving instructions to both content
owners and license issuers to increase the security of the whole
process.
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Ads and adware
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FairPlay
What it is FairPlay?
Restrictions
Brief Technical Description
Is FairPlay “fair”? ITunes bussines model
Harmony technology (RealNetworks)
 Reverse-Engineering against Apple
Jon Johansen, PyMusique
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FairPlay
Key terms:
• iTunes Music Store: online music service.
• iTunes: digital media player.
• iPod: portable media player.
• FairPlay: Apple’s DRM technique
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Restrictions
A protected track:
• may be copied to any number of iPod players.
• may be played on up to five authorized computers
simultaneously.
• may be copied to a standard CD audio track any number
of times.
A particular playlist within iTunes containing a protected
track can be copied to a CD only up to seven times.
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Brief Technical Description
• FairPlay’s protected files are regular mp4
container files with an encrypted AAC
(Advanced Audio Coding) audio stream.
• User key and Master key
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Purchase Process
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Authorize / Deauthorize
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iPod
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Is FairPlay “fair”?
• No portable player aside from the iPod supports
FairPlay.
• iPod only supports the AAC and MP3 standard, no WMV.
• Expecting profits in iPod sales, allows Apple to drop
prices in the iTunes Music Store.
• Key strategy from Apple’s business model:
Using software to drive hardware sales.
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Harmony
• Introduced by RealNetworks in July 2004.
• Harmony allows RealPlayer Music Store to play their
songs on the iPod.
• RealNetworks uses a different protection scheme
incompatible with FairPlay.
• How? Harmony transparently converts a RealNetworks
protected file to a FairPlay-compatible protected file.
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Harmony
• RealNetworks argued they freed consumers “from the
limitation of being locked into a specific portable device
when they buy digital music”.
• A cat and mouse game started between Apple and
Harmony.
• RealNetworks was criticized for:
– Keeping its own intellectual property and products closed, while
asking Apple to open up the iPod.
– Attempting to force Apple into a partnership that would only
benefit RealNetworks.
• Finally, afraid of a lawsuit from Apple, RealNetworks
gave up trying to break Apple’s technology.
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Reverse-Engineering
• Many efforts have been made to circumvent the encryption of
FairPlay-protected files.
• Most of attacks consisted on removing the encryption from FairPlayprotected files.
• So far, all applications have two things in common:
– They use the user keys from the key repository, which ensures
they can decrypt only files that are legally bought.
– They keep the metadata inside the MP4 container intact, so is
possible to identify the user who originally bought the file after it
is decrypted.
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Reverse-Engineering
• Jon Johansen
– The DRM anti-hero or the anti-DRM hero.
– In March 2005, he released via his own website PyMusique, for
the purpose of allowing downloads from the iTunes Music Store.
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PyMusique
• Works as a front-end to iTunes Music Store, emulating iTunes'
connection to the online music store.
• Allows the download of purchased files from the iTunes Music Store
without DRM encryption.
• This was possible because iTunes software adds the DRM to the
music file after the music file is downloaded.
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PyMusique
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PyMusique
• Legal aspects:
– Accessing iTunes Music Store through a third-party application is
a violation of the Terms of Service.
– Users who purchase music through PyMusique are doing so in a
manner not consistent.
• On March 22, Apple released a patch for the iTunes Music Store
blocking the use of the PyMusique program.
• In September 2005, Jon Johansen released SharpMusique, which
took over where PyMusique left off.
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Conclusions
• It could be argued that Microsoft's WMA
now looks stronger than iTunes.
• WMA will also be cracked.
• People against DRM will support reverseengineering.
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Questions?
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Thanks for your attention!
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