U.S. patent application number 12/772404 was filed with the patent office on 2010-08-19 for digital rights management in a distributed network.
Invention is credited to Lakshminarayanan Gunaseelan, Abdul Salam Faisal Padinjareveetil.
Application Number | 20100211776 12/772404 |
Document ID | / |
Family ID | 35461685 |
Filed Date | 2010-08-19 |
United States Patent
Application |
20100211776 |
Kind Code |
A1 |
Gunaseelan; Lakshminarayanan ;
et al. |
August 19, 2010 |
Digital rights management in a distributed network
Abstract
The present invention is implemented within a distributed
network operating environment (such as a CDN) in which content
providers offload given content for delivery from servers (e.g.,
CDN edge servers) managed by a service provider (such as a CDN
operator). It is assumed that the given content is secured using a
digital rights management (DRM) scheme. According to the invention,
a distributed set of license server processes are provided to
manage the issuance of content licenses. Each of the license server
processes is operative to generate licenses by which a given end
user client obtains given rights for given content, typically the
content served from the machine. A distributed set of license
server processes operates in a de-centralized manner and without
access to third party business logic (e.g., a payment mechanism) or
authentication information associated with end users requesting the
given content.
Inventors: |
Gunaseelan; Lakshminarayanan;
(Milpitas, CA) ; Padinjareveetil; Abdul Salam Faisal;
(Foster City, CA) |
Correspondence
Address: |
LAW OFFICE OF DAVID H. JUDSON
15950 DALLAS PARKWAY, SUITE 225
DALLAS
TX
75248
US
|
Family ID: |
35461685 |
Appl. No.: |
12/772404 |
Filed: |
May 3, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11148899 |
Jun 9, 2005 |
7711647 |
|
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12772404 |
|
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|
60578670 |
Jun 10, 2004 |
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Current U.S.
Class: |
713/165 ;
726/26 |
Current CPC
Class: |
G06F 21/10 20130101;
G06F 2221/0786 20130101; G06Q 10/10 20130101; G06Q 30/06
20130101 |
Class at
Publication: |
713/165 ;
726/26 |
International
Class: |
G06F 21/00 20060101
G06F021/00 |
Claims
1. Apparatus operative in a distributed network in which content
providers offload given content for delivery from servers managed
by a content delivery network service provider, wherein the given
content is secured by a digital rights management scheme,
comprising: a distributed set of license server processors that
operate autonomously from one another to enable decryption keys to
be generated and managed from individual license server processors
in a de-centralized manner and without access to authentication
information associated with end users requesting the given content;
wherein at least one license server processor comprises a
processor, and computer memory associated with the processor and
holding computer program instructions that when executed by the
processor generates a license by which an end user client obtains
rights for content.
2. The apparatus as described in claim 1 wherein one or more rights
in the license are established by the license server processor
dynamically on a per request basis.
3. Apparatus operative in a distributed network in which content
providers offload given content for delivery from servers managed
by a content delivery network service provider, wherein
authorization to access the given content is obtained through
business logic and the given content is secured by a rights
management (DRM) scheme, comprising: a distributed set of license
server processors that operate autonomously from one another to
enable DRM licenses to be generated and managed from individual
license server processors in a de-centralized manner and without
access to the business logic or any authentication information
associated with end users requesting the given content: wherein at
least one license server processor comprises a processor, and
computer memory associated with the processor and holding computer
program instructions that when executed by the processor generates
a license by which an end user client obtains rights for
content.
4. The apparatus as described in claim 3 wherein the rights in the
license are established by the license server processor based on
data in a metadata file associated with the license server
processor.
5. The apparatus as described in claim 3 wherein the rights in the
license are established by the license server processor dynamically
on a per request basis based on data in a token.
6. The apparatus as described in claim 5 wherein, following
verification of the token, the license server processor generates
the license by extracting one or more parameters from a request
query, creating a key object, and creating a rights object.
7. The apparatus as described in claim 6 wherein the license server
processor generates the license by creating a license object from
the key object and the rights object.
Description
[0001] This application is a continuation of Ser. No. 11/148,899,
filed Jun. 9, 2005, now U.S. Pat. No. 7,711,647, which application
was based on and claimed priority from Provisional Application Ser.
No. 60/578,670, which was filed Jun. 10, 2004.
BACKGROUND OF THE INVENTION
[0002] 1. Technical Field
[0003] The present invention relates generally to techniques for
content delivery.
[0004] 2. Description of the Related Art
[0005] It is known in the art for a content provider to outsource
its content delivery requirements to a content delivery network (a
"CDN"). A content delivery network is a collection of content
servers and associated control mechanisms that offload work from
Web site origin servers by delivering content on their behalf to
end users. A well-managed CDN achieves this goal by serving some or
all of the contents of a site's Web pages, thereby reducing the
customer's infrastructure costs while enhancing an end user's
browsing experience from the site. For optimal performance, the CDN
service provider may maintain an objective, detailed, real-time
view of the Internet's topology, reliability, and latency, and this
view may then be used to power a dynamic DNS-based system to direct
end users to the best CDN server to handle a particular
request.
[0006] Digital Rights Management (DRM) refers to the technology
used for the protection of digital media content, typically audio
or audiovisual works. DRM works by encrypting the content before
distribution, and by limiting access to only those end-users who
have acquired a proper license to play the content. The DRM license
enforcement is done at the player/client, and therefore, the
integrity of the client-side (of DRM) is critical for the scheme to
work. Microsoft, Real and Apple have developed proprietary DRM
technologies for their audio and audiovisual content distribution.
Apple's DRM technology is used in its iTunes music service.
Microsoft and Real Networks support DRM protection for both
on-demand and live media content. There are some standardization
efforts around DRM (MPEG4/ISMA and Open Mobile Alliance), but these
standards are still in the specification stage.
[0007] An end-to-end DRM system typically comprises three (3)
parts: encryption, business-logic and license-delivery. DRM starts
with the encryption of the content. Once the content is encrypted,
a key is required to unlock the content. The encrypted content can
be delivered through any number of delivery methods: HTTP,
streaming, FTP, P2P, email, or the like. An end-user who desires to
play the content visits an e-commerce web site and transacts with
the business-logic process, usually involving one of registration,
login, and/or payment; once this is done, the end-user is issued a
license to play the content. The issued license typically comprises
(i) a key (for decrypting the content), (ii) a set of rights (e.g.
play exactly once, play for 30 days, or the like), and (iii) with
the property that the license is valid only on the end-user machine
to which it is issued. When an end-user attempts to play the DRM
protected content, the player first checks the license cache on the
machine, and if a license is found, the playback starts by
decrypting the content. If a license is not found, the player
attempts to get a license, typically from the storefront URL that
is embedded in the content. Ultimately, it is the player/client
that enforces the DRM. In a typical DRM scenario, a media file
(e.g., a stream) is encrypted by a packager component using a key.
Alternatively, the stream can be encrypted on the fly by an
encoder. A streaming Server serves the encrypted stream to an end
user browser's media player. As noted above, the player needs to
get a license (which includes the key) from a license server to
decrypt and play the content.
[0008] In the past, administration and management of the DRM
license keys has taken place in a centralized manner, primarily to
address security issues. It would highly desirable to be able to
leverage the distributed nature of a content delivery network to
facilitate a distributed (non-centralized) license delivery
infrastructure. This present invention addresses this need.
BRIEF SUMMARY OF THE INVENTION
[0009] It is an object of the present invention to provide a
distributed architecture for digital rights management (DRM)
license delivery.
[0010] It is a further object of the invention to leverage the
distributed infrastructure of a content delivery network (CDN) to
enable management and distribution of DRM license keys, preferably
in a non-centralized (i.e., distributed manner).
[0011] It is another object of the invention to provide for a
distributed architecture for license delivery wherein the entity
(e.g., the CDN) that provides the license key distribution does not
maintain or have access to identifying information for the
anticipated users of the protected content.
[0012] Thus, the present invention envisions a distributed license
delivery infrastructure that is separate from any centralized
database in which is stored information about the end users that
may desire to obtain the content protected by the license. An
advantage of this solution is that is separates the business logic
from any validation scheme, and hence allows content providers to
implement flexible business rules that are appropriate for their
business. In a preferred embodiment, the CDN service provider need
not maintain a database of all the end-users of the CDN customers.
The CDN provides license delivery but is not directly involved in
authenticating the requesting end-user's identity, collecting
payment or obtaining credit-card information; rather, the CDN
simply authenticates the end-user's request (as opposed to the
user) before issuing the license and, ultimately, delivering the
stream. The invention thus separates the business-logic from
license delivery in the context of a DRM-implemented CDN solution
offering.
[0013] It is a further general object of the present invention to
facilitate music distribution and subscription-based media services
over a content delivery network (CDN).
[0014] Generalizing, the present invention is implemented within a
distributed network operating environment (such as a CDN) in which
content providers offload given content for delivery from servers
(e.g., CDN edge servers) managed by a service provider (such as a
CDN operator). It is assumed that the given content is secured
using a digital rights management scheme. According to the
invention, a distributed set of license server processes are
provided to manage the issuance of content licenses. Each of the
license server processes are operative to generate licenses by
which a given end user client obtains given rights for given
content. The distributed set of license server processes operates
in a de-centralized manner and without access to authentication
information associated with end users requesting the given
content.
[0015] The foregoing has outlined some of the more pertinent
features of the invention. These features should be construed to be
merely illustrative. Many other beneficial results can be attained
by applying the disclosed invention in a different manner or by
modifying the invention as will be described.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a block diagram of a known distributed network
(such as a content delivery network) in which the present invention
may be implemented; and
[0017] FIG. 2 illustrates a typical machine configuration for an
edge server in the distributed network of FIG. 2;
[0018] FIG. 3 illustrates the basic components of a DRM solution
that is implemented in a CDN according to the present
invention;
[0019] FIG. 4 is a more detailed description of how DRM-protected
content is delivered by the CDN;
[0020] FIG. 5 illustrates a token validation process performed by a
CDN license server process;
[0021] FIG. 6 illustrates how the CDN license server process
generates and delivers the license; and
[0022] FIG. 7 illustrates a dynamic rights object that may be
created and used by a license server to enforce dynamic license
rights on a per request basis.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0023] It is known to deliver digital content (e.g., HTTP content,
streaming media and applications) using an Internet content
delivery network (CDN). A CDN is a network of geographically
distributed content delivery nodes that are arranged for efficient
delivery of content on behalf of third party content providers.
Typically, a CDN is implemented as a combination of a content
delivery infrastructure, a request-handling mechanism (preferably
based in DNS), and a distribution infrastructure. The content
delivery infrastructure usually comprises a set of "surrogate"
origin servers that are located at strategic locations (e.g.,
Internet network access points, Internet Points of Presence, and
the like) for delivering content to requesting end users. The
request-handling mechanism (typically a set of name servers)
allocates servers in the content delivery infrastructure to
requesting clients in a way that, for web content delivery,
minimizes a given client's response time and, for streaming media
delivery, provides for the highest quality. The distribution
infrastructure consists of on-demand or push-based mechanisms that
move content from the origin server to the surrogates. An effective
CDN serves frequently accessed content from a surrogate that is
optimal for a given requesting client. In a typical CDN, a single
service provider operates the request-handlers, the surrogates, and
the content distributors. In addition, that service provider
establishes business relationships with content publishers and acts
on behalf of their origin server sites to provide a distributed
delivery system.
[0024] As seen in FIG. 1, an Internet content delivery
infrastructure usually comprises a set of "surrogate" origin
servers 102 that are located at strategic locations (e.g., Internet
network access points, and the like) for delivering copies of
content to requesting end users 119. A surrogate origin server is
defined, for example, in IETF Internet Draft titled "Requirements
for Surrogates in the HTTP" dated Aug. 9, 2000, which is
incorporated herein by reference. The mechanism 104 allocates
servers 102 in the content delivery infrastructure to requesting
clients. Typically, the mechanism 104 is implemented within (or as
an adjunct to) a DNS subsystem managed by the CDN service provider.
The distribution infrastructure consists of on-demand or push-based
mechanisms that move content from the origin server to the
surrogates. A CDN service provider (CDNSP) may organize sets of
surrogate origin servers as a group or so-called "region." In this
type of arrangement, a CDN region 106 typically comprises a set (or
cluster) of one or more content servers that share a common
back-end network, e.g., a LAN, and that are located at or near an
Internet access point. Thus, for example, a typical CDN region may
be co-located within an Internet Service Provider (ISP) Point of
Presence (PoP) 108. A representative CDN content server is a
Pentium-based caching appliance running an operating system (e.g.,
Linux, Windows NT, Win2K) and having suitable RAM and disk storage
for CDN applications and content delivery network content (e.g.,
HTTP content, streaming media and applications). Such content
servers are sometimes referred to as "edge" servers as they are
located at or near the so-called outer reach or "edge" of the
Internet. The CDN typically also includes network agents 109 that
monitor the network as well as the server loads. These network
agents are typically co-located at third party data centers or
other locations. Mapmaker software 107 receives data generated from
the network agents and periodically creates maps that dynamically
associate IP addresses (e.g., the IP addresses of client-side local
name servers) with the CDN regions.
[0025] Content may be identified for delivery from the CDN using a
content migrator or rewrite tool 106 operated, for example, at a
participating content provider server. Tool 106 rewrites embedded
object URLs to point to the CDNSP domain. A request for such
content is resolved through a CDNSP-managed DNS to identify a
"best" region, and then to identify an edge server within the
region that is not overloaded and that is likely to host the
requested content. Instead of using content provider-side migration
(e.g., using the tool 106), a participating content provider may
simply direct the CDNSP to serve an entire domain (or sub-domain)
by a DNS directive (e.g., a CNAME). In either case, the CDNSP may
provide object-specific metadata to the CDN content servers to
determine how the CDN content servers will handle a request for an
object being served by the CDN. Metadata, as used herein, refers to
a set of control options and parameters for the object (e.g.,
coherence information, origin server identity information, load
balancing information, customer code, other control codes, etc.),
and such information may be provided to the CDN content servers via
a configuration file, in HTTP headers, or in other ways. The
Uniform Resource Locator (URL) of an object that is served from the
CDN in this manner does not need to be modified by the content
provider. When a request for the object is made, for example, by
having an end user navigate to a site and select the URL, a
customer's DNS system directs the name query (for whatever domain
is in the URL) to the CDNSP DNS request routing mechanism. A
representative CDN DNS request routing mechanism is described, for
example, in U.S. Pat. No. 6,108,703, the disclosure of which is
incorporated herein by reference. Once an edge server is
identified, the browser passes the object request to the server,
which applies the metadata supplied from a configuration file or
HTTP response headers to determine how the object will be handled.
The CDN may also include other infrastructure, such as a
distributed data query and collection system that collects usage
and other data from the edge servers, aggregates that data across a
region or set of regions, and passes that data to other back-end
systems to facilitate monitoring, logging, alerts, billing,
management and other operational and administrative functions.
[0026] As also seen in FIG. 1, the CDNSP also may operate a
metadata transport system 116 comprising a set of one or more
servers to enable metadata to be provided to the CDNSP content
servers. The transport system 116 may comprise at least one control
server 118, and one or more staging server 120a-n, each of which is
typically an HTTP server (e.g., Apache). Metadata is provided to
the control server 118 by the CDNSP or the content provider (e.g.,
using a secure extranet application) and periodically delivered to
the staging servers 120a-n. The staging servers deliver the
metadata to the CDN content servers as necessary. Metadata is
useful for controlling how the content is managed at the edge
server.
[0027] The above described content delivery network is merely
illustrative. The present invention may leverage any content
delivery infrastructure.
[0028] FIG. 2 illustrates a typical machine configuration for a CDN
content edge machine, sometimes referred to generally as a server.
Typically, the machine 200 comprises commodity hardware running an
operating system 202. The machine may optionally include a virtual
machine 204 and an application server 206 to facilitate the
execution of one or more customer application or application
components 210. For handling HTTP content, the machine 200
typically implements a cache 212. The machine also includes a store
for customer configuration data 214, typically in the form of
customer-specific metadata, which controls how content is managed
on the machine. A server manager 216 overlays and controls the
cache 212, using the customer configuration data. For streaming
media, the machine includes one or more media servers 215, such as
a Windows Media Server (WMS), as required by the supported media
formats. The server manager 216 may also control the media server
according to the customer configuration data. System management 218
and system security 220 modules are also provided to facilitate
these and other conventional functions. The machine may also incude
logging processes, name server processes, data aggregation
processes, and the like. For purposes of the present invention, as
will be described below, a given machine includes a rights
management license server process 225, which faciliates a
de-centralized DRM-based license serving model. The license server
process 225 serves DRM licenses for the protected content served
from the machine, or for the protected content served from machines
co-located with the machine.
[0029] By way of additional background, digital rights management
(DRM) solutions are well-known in the art. One such known DRM
system available from Microsoft Corporation includes a Digital
Rights Manager that can be integrated into a content delivery
network (CDN) according to the present invention. In this example,
a Windows Media Rights Manager helps protect digital media (such as
songs and videos) by packaging digital media files. The present
invention is not limited to use with DRM solutions from any
particular vendor, of course. Indeed, the present invention assume
the existence of a third party DRM solution (available from a DRM
solutions provider) and concerns how that solution (and, in
particular, the license server(s)) may be implemented within the
CDN, taking advantage of the CDN's distributed or de-centralized
infrastructure.
[0030] In a typical DRM solution, a packaged media file is a
version of the media file that has been encrypted and locked with a
key. In the Microsoft DRM solution, keys are created and used in
the Windows Media Rights Manager. In particular, the key used to
encrypt the content is computed from a seed and a KeyID, namely:
Seed+KeyID=Key. Typically, for purposes of the present invention,
one seed will be chosen per content provider, and this seed is then
used to encrypt all of content provider's content. The KeyID
component is designed to vary by file. The content provider may use
a different KeyID per file, or alternatively, it may choose to
encrypt all of its files (or a collection of files) using a single
KeyID. A license issued for a given KeyID will apply to all the
files encrypted using the same KeyID. To generate a key, a license
key seed and a key ID are needed. The license key seed is a value
that is known only to the content owner and the DRM license server.
The content owner creates a KeyID for each protected file. This
value is included in the packaged file. When the license server
needs to issue a license for a packaged file, a key can be
recreated by retrieving the key ID from the packaged file. The
Windows Media License Service uses the license key seed and the key
ID from the packaged file to create a key. The key is included in
the license sent to the end user's computer. Using the key included
in the license, the player on the consumer's computer can open and
play the protected file.
[0031] FIG. 3 illustrates the inventive DRM CDN solution. The three
(3) primary components of the full end-to-end DRM solution are (i)
packager 300 (ii) license server 302 and (iii) E-commerce
storefront (or its equivalent) 304. The packager 300 typically is
software (a set of program instructions executable on a processor)
used to encrypt the content. This software may run at a CDN
customer premise (an origin server), or on one or more CDN servers.
The license servers 302 issue licenses to end-users' players and
are managed by the CDN. According to a technical advantage of the
present invention, the license servers 302 operate in a distributed
or de-centralized manner, leveraging the basic infrastructure of
the CDN itself, as opposed to operating in a centralized manner of
the prior art. The E-commerce storefront 304 preferably is set up
and managed by the content provider or some third party on the
content provider's behalf. The following process flow illustrates
the basic operation of the invention. At step (1), an end-user
visits the content provider's web site and performs a business
transaction. After registration/login and/or payment collection,
once the content provider decides to make the content available to
the end-user, the content provider's site generates a token (using
the shared-secret agreed between the CDN service provider and the
content provider) and sends the end-user's browser (the player) to
the CDN license server. Typically, this will be done in the
background while the end-user stays on the content provider's site.
At step (2), the License server validates the token presented by
the end-user's browser. The token usually has information to issue
the license to `"user U with rights R for content C." The license
server first validates the token using the shared secret to ensure
that the token has been issued by the content-provider's site. Once
the token is found to be valid, it generates and issues a DRM
license <U, R, C> to the end-user. Typically, this entire
step 2 will be transparent to the end-users. Alternatively, the
content provider's site can choose to get the license itself
directly from the CDN license servers and forward the license to
the end-user. This is shown as step 2' in FIG. 3. This latter
approach ensures a much more secure workflow as the license servers
can be configured (e.g., via metadata access control lists (ACLs))
to issue licenses only to the content provider's web-servers. At
step (3), the end-user clicks on the URL at the content provider's
site to play a stream. This request will hit a CDN streaming
server. The streaming server will send the encrypted content to the
player. The playback will start since a license is already present.
In the event a user attempts to play a piece of content directly
from a CDN server without first going the content provider's site,
the store-front URL embedded in the content would direct the
end-user's player to the content-provider's site.
[0032] FIG. 4 illustrates this process in more detail for streaming
or on-demand media content delivery. At step 0, the CDN supplied
packaging program 400 generates a key, generates and signs the
content header, and then encrypts the file (e.g., a Windows media
file) with this information. The content header of a packaged media
file contains the following information: KeyID and license
acquisition URL. At step 1, an end-user visits the content
provider's web site 402 and performs a business transaction. After
registration/login and/or payment collection, once the content
provider decides to make the content available to the end-user, the
content provider's site 402 generates a token (using the
shared-secret agreed between the CDN and the content provider) and
does one of the following depending on a selected security model:
(a) the customer site contacts a CDN license server 404 to get a
license; this is shown as step 3 in FIG. 4, or (b) the customer
site sends the end-user's browser to the CDN license server
(usually this will be done in the background while the end-user
stays on the content-provider's site); this is shown as step 3' in
FIG. 4. As seen in the drawing, at step 2, the CDN-supplied
tokenizer 406 (a software program, process, thread, or the like)
generates a token, preferably using a shared-secret agreed between
the CDN service provider and the content provider, and this token
is used to contact a CDNSP DRM license server 404. This process is
described in more detail below. At step 3, the CDN license server
404 validates the token presented by the customer site (or
end-user's browser). The token usually has information to issue the
license to "user U with rights R for content C." Preferably, the
license server 404 first validates the token, preferably using a
token salt, and ensures that the token has been issued by the
content provider's site. Once the token is found to be valid, it
generates and issues a DRM license that contains a key to decrypt
the encrypted content at the player. This process is also described
in detail. At step 4, the end user attempts to access the protected
content and plays the content. If the end user does not have a
valid license, the end user needs to get a license. The Content
header of the encrypted file (or live stream) includes the license
acquisition URL. When an end user tries to play a DRM protected
media file that does not have a license, the player opens the
license acquisition URL and attempts to get the license. Typically
this will be a URL to the content provider's web site asking for a
registration/subscription renewal or payment (i.e. step 1).
[0033] Before the CDN can begin issuing licenses for a customer's
DRM protected content, several secrets must be provisioned and
shared by the CDN and its customer. The following describes the
process for two types of streaming media. The secrets are generally
broken down into secrets required for packaging content (both for
live and on-demand), and secrets required for token generation. In
one embodiment, the CDN may provide the customer with an
application, which will allow either the CDNSP or the customer to
generate all required, shared secrets. These shared secrets must be
kept secret and communicated to the other party over some secure
channel. Provisioning for on-demand video typically will require
generation of a DRM VOD XML file (sometimes referred to as a DRM
VOD Specification) that the user loads into the CDN packager tool
to package files using this set of shared secrets. Required tags
would include Key_seed, an encryption seed, Header_private_key, a
private key for signing a header, Header_public_key, a public key
for signing a header, License_URL, a license acquisition URL, and
Individualization, a required client individualization level.
Additional tags (keys and certificates) may be implemented as well.
The provisioning tool may rely on a DRM provider's SDK (e.g.,
Windows Media Format SDK) to generate seeds and keys. Provisioning
for live video requires the generation of a DRM profile export
file, which typically is a password-protected encrypted file that
includes information necessary for an encoder to generate a
DRM-protected live stream compatible with the CDNSP license server,
together with an XML file (sometimes referred to as a DRM Live
Specification) that includes a Key_seed tag and a Header_public_key
tag and their associated values. The latter file may also include a
Profile_import_password tag that defines a password for importing
an associated DRM profile Likewise, the provisioning tool may rely
on the DRM provider's SDK to generate the DRM profile.
[0034] In a representative embodiment, there are two additional
shared secrets needed for token generation and parsing. A token
salt is required for MD5 digest calculation for the DRM token. A
base 64-encoded 128-bit Rijndael key may be used to encrypt an
optionally included encryption Seed and public key. The customer
and the CDN must share these values securely for successful secure
license delivery. The Rijndael key is not necessary for all token
generation scenarios.
[0035] Once the customer has decided to issue a license to an
end-user, it must communicate the details of this desired license
to the CDN license server. This information may be communicated in
the URL used by the end-user client (e.g., an end user browser
media player) to request a license, e.g., a token in the form of a
query string. The following section will describe the format of the
query string and the workflows that determine which optional
components of the query string may be used. In a representative
embodiment, there are two major provisioning/token generation
workflows: shared secrets in metadata, and shared secrets in query
string. In the first workflow, a customer uses a CDN DRM
provisioning tool to generate a DRM VOD Specification (along with
its associated DRM Profile) and/or an DRM Live Specification. The
values in the generated specifications are securely communicated to
the CDNSP are entered in the CDN's metadata transport system
(reference number 116 in FIG. 1) under a specification identifier.
In this case, when the customer generates a query string token for
use in license delivery, it will specify this identifier in the
query string. In the second workflow, it is assumed that the
customer does not want to add their shared secrets (encryption seed
and public key) to metadata (or perhaps because the CDN does not
implement such a transport system). This may be due to security
concerns on the part of the customer, or because the particular
workflow of the customer requires frequent specification
generation. In this case, the customer (or some third party on the
customer's behalf) manages its own database of encryption seeds and
public keys. They are communicated to the CDN license server in the
query string during each license request. To maintain security for
these two secrets, preferably they are encrypted using the Rijndael
cipher before being placed in the query string. The Rijndael key
used for this encryption may be provisioned per-customer and may be
stored on the license server in metadata associated with that
customer. A specification identifier is specified in this case as
well, and this identifier may be used to determine the token salt
and Rijndael key.
[0036] Preferably, the CDN license server (a program, process,
execution thread, or the like) responds to license requests with a
valid DRM license only if the request has a valid token associated
with it. As noted above, preferably the token is generated at the
customer's site using CDN-supplied tools. A representative URL for
a DRM license request to a CDN license server may take the form:
http://abc.wm.edgedrm.net/getLicense?<query string>, where
<query string> is a series of name-value pairs taking the
form "name=value", with successive name-value pairs are separated
by ampersands. The required names recognized by the license server
are set forth below in Table 1:
TABLE-US-00001 TABLE 1 Name Description Value Type Drm Token type
and flags A single digit followed by base64-encoded flag word
Digest MD5 token digest Base64-encoded 16-byte MD5 digest Keyed Key
ID Cleartext string Ts Token creation time, in Cleartext 32-bit
integer GMT seconds-since-epoch specID Spec ID Cleartext 32-bit
integer rightsID Rights ID Cleartext 32-bit integer
The Token type and flag indicates the token type, and a 16-bit bit
field of flags indicates the required presence of any optional
query string parameters. The defined bit values are listed in the
following Table 2. A query string parser will ignore flag bits that
are set but undefined.
TABLE-US-00002 TABLE 2 Query string flag bitmap definitions
Required Query String Component Flag Value Time window 0x0001
Encryption seed 0x0002 Public key 0x0004 cInfo 0x0008 Chg
0x0010
An MD5 digest is calculated at token generation time and included
in the query string. The license server recalculates the digest
upon reception of a license request and verifies that the digest is
identical before processing the request. Preferably, the digest is
calculated over the values of all recognized name-value pairs
included in the query string, other information in the request URL,
and a secret Token salt that is shared by the license server and
the customer. The required timestamp is the token creation time.
The optional time window parameter is used to prevent license
re-acquisition for an expired license by simply resending the
original license request. If the time window parameter is not found
in the query string, the license server may use a value specified
in metadata for the given customer. The query string must contain a
specification identifier. An encryption seed/public key pair can
appear in the query string. If encryption seed and public key are
found in the query string, these values will be used during license
generation. If encryption seed and public key are not in the query
string, the encryption seed and public key associated with the
specified (in query string) specification identifier are taken from
the metadata. If the rights ID is not specified in the query
string, the license server will use the default rights profile as
specified in the metadata to generate the license. A license is
bound to a particular client machine by the inclusion of a
ClientInfo string generated on the requesting client machine. The
string contains one or more pieces of data, such as an encrypted
client ID, version information about given software on the end
user's computer, other version information associated with the
individual, or the like. The ClientInfo string is required to
generate the license, and it ensures that the license is only good
on the machine from which the end-user originally attempted to
obtain the license. The particular manner by which the ClientInfo
string is generated is DRM-implementation specific and outside the
scope of the present invention.
[0037] In a representative embodiment, customer specific
information is stored in per-customer metadata. A representative
metadata file would include the following information: license key
seed (the shared secret between the CDNSP and the customer for
content encryption), the token salt (a value shared between the
CDNSP and the customer to compute the token digest), a public key
(used for signing the license), a customer code (used to identify
the customer to the CDN), a fail action URL (the customer's Web
site URL, as license requests with invalid tokens would be
re-directed here), a Rijndael key (used to decrypt the license key
seed if supplied as part of the token), a priority value (used if
the customer has multiple licenses for a single content item),
Rights ID, and Specification ID. The content provider can specify a
list of rights-profiles. A rights-profile describes a specific set
of rights to be issued with a license. A customer would typically
set up one or more of such rights profiles in metadata and indicate
the Rights ID to be used for a given license in the token sent with
the license request. As noted above, users have an option to
specify the encryption seed and public key through the query string
or they can associate an encryption Seed and public key to the
specification identifier passed as part of the query string. The
CDN license server uses the specification identifier to choose the
matching shared secrets from metadata and uses the secrets to
generate the license. Although not required, by specifying a
different Specification ID the shared secrets can be rotated. This
is useful mainly for rotating the token generation related secrets.
The CDN customer may require that the files be played only on an
application that has been "individualized" by specifying a minimum
individualization version number (this number may be included in
the ClientInfo string). If a consumer tries to play a media file
that requires individualization using a player that has not been
individualized, a license is not issued and the player prompts the
consumer to get a security upgrade.
[0038] The following provides details regarding the CDN license
server. In an illustrative embodiment, the license server is a
process running at an edge server acting as the license server. The
process listens on a given port (e.g., port 8083) and accepts DRM
requests from end user browser media players (or the like). If
necessary, a customer site preferably contacts a license server
process with the DRM request on port 80, and this request is then
tunneled to the license server process on the given port. The edge
server license process listens on the given port and accepts
requests such as HTTP GET or POST requests. As has been described,
the process takes input from a user supplied token and customer
metadata parameters (e.g., encryption key seed, which is used to
protect the content, and token salt, which is used to protect the
token) to generate a license. In operation, there are two major
steps performed during this process: validating the supplied token,
and license generation and delivery. The token validation process
is illustrated in the flowchart of FIG. 5, and the license
generation and delivery process is illustrated in the flowchart of
FIG. 6.
[0039] As illustrated in FIG. 5, a DRM request to the CDN license
server process always contains a token in the form of query string.
The request will not be processed if the token present is not
valid. To check validity of the token, the edge server license
process creates a dummy token digest using the same scheme
mentioned in the token generation section above. It then compares
the generated token digest with the supplied digest. If they match,
the license server process assumes that the request is valid. Thus,
with respect to FIG. 5, the routine starts at step 502 by
extracting parameters from the request's query string. A test is
then performed at step 504 to determine whether a given time
associated with the token has expired. If so, the routine branches
to step 506 and issues a "no license" redirect to the customer's
site (and/or, in the alternative, logs an access denied error). If,
however, the outcome of the test at step 504 is negative, the
license server process computes the digest using the query
parameter and the metadata information. This is step 508. A test is
then performed at step 510 to determine if the digest matches that
associated with the token. If the outcome of the test at step 508
is negative, the routine issues the "no license" redirect at step
506. If, however, the outcome of the test at step 510 is positive,
the token is validated and the license is then generated at step
512.
[0040] FIG. 6 illustrates the license generation process. As noted
above, the license includes at least the key to play the encrypted
content, as well as the rights and conditions of the license, and
it may also include other information (e.g., priority value,
attributes identifying the CDN, or the like) as may be desired or
required by the particular DRM solution. The routine begins after
the server process has validated the token, as described in FIG. 5.
At step 602, the routine extracts parameters from the request's
query string. At step 604, a test is performed to check the
ClientInfo string (e.g., client capability, version, etc.) or the
like. If the outcome of the test at step 604 indicates an issue,
the routine branches to step 606 and issues a "no license"
redirect, logs an error, or the like. If, however, the outcome of
the test at step 604 is positive, the routine continues at step 608
to create a key object using the Key_ID and license key seed.
During this step the server process also creates a rights object
using the Rights_ID and the defined license rights. At step 610,
the server process then creates a license object using the key
object, rights object and Key_ID, and signs the license. At step
612, a test is performed to determine if there were any errors in
the creation of the various objects. If so, the routine branches
back to step 606. If, however, the outcome of the test at step 612
is negative, the routine continues at step 614 to construct the
license (preferably as an XML file) and to deliver that license to
the requesting end user's browser media player (or other rendering
engine, as the case may be).
[0041] Although the license server process has been described as a
single entity, this is not a requirement. One or more of the
functions may be implemented in one or more execution threads, or
multiple threads or processes may be implemented. Generalizing, any
set of one or more processes, programs, threads, or the like that
provide the token validation and license generation functions may
be implemented in a given edge server. The license server may also
include ancillary functions such as data logging, load reporting,
and the like, to store and export operational data to other CDN
processes. Moreover, it is not required that the license server
process be distinct from the other edge server processes (e.g.,
metadata handling, object caching, or the like). Further, it is not
required that each edge server in the CDN (or even in a given
region) support the server license process. There may be a
dedicated subset of server license machines running in the CDN,
albeit in a distributed manner. According to the invention,
however, it is not anticipated that there will be any centralized
place where license keys for the CDN-sourced content are generated.
As used herein, a "license server process" should be broadly
construed as given software instructions, program sequences, code
portions, and the like, executable by one or more processors.
According to the invention, a set of such processes provide
distributed license serving and operate in a de-centralized manner,
preferably without access to authentication information associated
with end users requesting the given content.
[0042] According to another feature of the present invention, in
addition to having license rights specified in the Rights_ID (which
are available in metadata in the CDN license server), the system
may be adapted to handle dynamic rights tokens. In this variant,
the CDN license server process manages different rights
dynamically, per request, which affords much greater flexibility in
handling rights per license and avoids metadata rights
provisioning. Preferably, dynamic rights are generated by the
tokenizer tool, using advanced options and inputs. The token
generator typically executes on the customer's Web site as
illustrated in FIG. 4. When using dynamic rights, the Rights_ID is
still needed in the license request. In this case, the license
server process first applies the rights specified by the Rights_ID,
and it then replaces or add rights as specified in the dynamic
rights license request. Table 3 below lists representative dynamic
rights and their semantics with given types of token generators
(e.g., Perl, ASP and Java):
TABLE-US-00003 TABLE 3 Representative Dynamic Rights ASP Properties
to Java Methods of WM Series 9 Right Description Perl Input Options
Dynamic Rights Object Dynamic Rights Class AllowBackupRestore
Boolean allowbackuprestore AllowBackupRestore setAllowBackupRestore
AllowBurnToCD Boolean allowburn AllowBurn setAllowBurn
AllowPlayOnPC Boolean allowplay AllowPlay setAllowPlay
BurnToCDCount Copy Count copycount CopyCount setCopyCount BeginDate
Calendar begindate BeginDate setBeginDate Date
DeleteOnClockRollback Boolean deleteonclockrollback
DeleteOnClockRollback setDeleteOnClockRollback
DisableOnClockRollback Boolean disableonclockrollback
DisableOnClockRollback setDisableOnClockRollback
ExpirationAfterFirstUse Calendar expirationafterfirstuse
ExpirationAfterFirstUse setExpirationAfterFirstUse Date
ExpirationDate Calendar expirationdate ExpirationDate
setExpirationDate Date ExpirationOnStore Calendar expirationonstore
ExpirationOnStore setExpirationOnStore Date MinimumAppSecurity
Security minimumsecurity MinimumSecurity setMinimumSecurity Level
MinimumClientSDKSecurity Client minimumclientsecurity
MinimumClientSDKSecurity setMinimumClientSDKSecurity Version
Playcount Play count playcount PlayCount setPlayCount
ExcludeApplication Exclude excludeapplication ExcludeApplication
excludeApplication app IDs
[0043] A representative example of how dynamic rights are
established is illustrated by the dynamic rights object shown in
FIG. 7. In this example, the content provider has created the
object using an ASP token generator. The content provider then sets
the desired properties with this object, and these properties may
then be applied on a per license request basis.
[0044] The present invention has numerous advantages. As noted
above, the invention provides for a highly scalable,
highly-available, distributed license server infrastructure,
together with the customary advantages of a CDN, which is used for
the delivery of the protected content. As noted above, in the
preferred embodiment, the invention provides that business logic
(payment processing, and the like) are separate from content
protection. This separation is enforced by having business logic
handled by the content provider (or some entity on its behalf)
while having the security (license serving) handed by the CDN,
which is also responsible for serving the protected content. This
enables CDN customers to implement flexible business rules that are
appropriate for their business model. Preferably, the CDN is not
involved in keeping track of its customer's end user's identity in
a database.
[0045] The present invention is not limited for use with any
particular type of content, such as streaming media, but is useful
for delivery of any protected content, including Web content,
software downloads, and the like. Also, as used herein, "protected"
content should be broadly construed to cover known or later
developed methods for securing content against unauthorized
activities at a given end user machine.
[0046] In addition, if desired, the CDN may implement a key
management infrastructure to manage the license keys generated by
the CDN license server processes.
* * * * *
References