Digital Rights Management in a 3G Mobile Phone and Beyond

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Digital Rights Management in a 3G Mobile Phone
and Beyond

• Thomas S.Messerges, Ezzat A. Dabbish
• Motorola Labs
• Young Sub Ko

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Contents

• Introduction
• DRM Concepts and strategies
• Our DRM system
• Security issues
• Family Domain
• Example use cases
• Conclusion

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Introduction

• 3G Mobile Phone
• High commmunication rates
• 144 Kbps, 384 Kbps, 2 Mbps depending on the mode
  of operation
• Personal Area Networking capability
• Peer-to-Peer sharing of digital items over
  short-range networks will be possible
• High Internet Connectivity
• More mobile phones than desktop computers
  connected to the Internet, soon
• Business opportunities for digital contents are
  attracting much interest
• Losses from piracy will mount
• Digital Items can be copied or shared at no cost
• Digital Rights Management(DRM) will be an
  essential component for in future mobile phones

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DRM CONCEPTS AND STRATEGIES - Overview of
Trusted DRM System

• License File
• Metadata
• Usage Rules
• How to deal with the content in DRM system
• Rights for content
• Content Encryption Key(CEK)
• Encrypt and decrypt the content
• Hash
• Link between the content and license
• Digital Signature
• For authenticity and integrity
• Protected Content File
• Encrypted Content
• Encrypted with key in the license File
• DRM System(When content is rendered)
• Rendering Software
• Pass the protected content file and License file
  to DRM Services software
• DRM Service
• Verify the signature of the license

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DRM CONCEPTS AND STRATEGIES - Open Mobile
Alliance DRM(OMA)
Issue Certificate
Mutual Authentication Using ROAP (RO Acquisition
Protocol)
Issue Certificate
Generate RO (Rights Object)
Generate DCF (DRM Content Format)
KPRIV Private Key KCEK Content Encryption
Key KREK Rights Encryption Key KMAC Message
Authentication Code Key
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DRM CONCEPTS AND STRATEGIES - Open Mobile
Alliance DRM(OMA)
Protected RO
RO
Encrypted Using REK (Symmetric Key)
Rights
Content Encryption Key (CEK)
Permission
Integrity for DCF
Digest of Content
Content ID
Authentication, Non-Repudiation, and Integrity
for Rights (Domain RO Only)
Digital Signature of Rights (Optional)
Encrypted Using Devices Public Key
Rights Encryption Key (REK) and MAC Key
Authentication, Non-Repudiation, and Integrity
for RO (Including REK Device RO)
MAC of RO
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DRM CONCEPTS AND STRATEGIES - Message
Authentication Code(MAC)
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OUR DRM SYSTEM - Interface for DRM

• Two approach noted in Schnecks paper
• Replace the I/O elements of OS with new modules
• Monitor all requests for I/O operations and
  inform a user if a proper license is not
  available
• Hyperadvisor
• Located between the OS and the hardware
• When an application requests access to a
  protected file, it would invoke the DRM system
• Our Approach
• OS is extended to support DRM functionality
• Access these extended system through API
• A header in a particular file indicates that it
  is protected
• If file is protected, extended API will be called

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OUR DRM SYSTEM - DRM manager

• Authenticate Licenses and Content
• Cryptographic hash of the content
• Verified by comparing computed hash based on the
  content with a hash in a license file
• For a mobile phone, the hash value are computed
  in a piecemeal fasion and form a hash table
• ? The hash table is verified incrementally as
  each portion of content is rendered
• Digital signature
• Verified using a public key of signer
• Security Agents will help cryptographic
  operations
• Enforce Rights
• Actions can be associated with three fundamental
  types of rights
• Render rights ,Transport rights, Derivative work
  rights
• The license have an additional event for
  performing an action
• Payments needs to be made or a play count needs
  to be decremented
• Secure database needed to track these events
• Rights to an action are assigned to a device
• DRM manager needs to have access to devices
  credentials(e.g., keys, certificates, IDs)
• A key/certificate manger is responsible for these
  credentials
• Decrypt Content
• Decrypt the content using key and route it to a
  trusted application

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OUR DRM SYSTEM - Trusted Application Agents

• Access and manipulate decrypted content
• Organized according to the type of action they
  perform
• Rendering agents, Transport agents, Derivative
  work agents
• Rendering Agents
• Provide the ability to render DRM-protected
  content
• e.g., a music player, a picture viewer
• The execution of a DRM-protected application is
  also rendering operation
• e.g., an application loader
• Transport Agents
• Provide services that move content from one
  location to another
• e.g., email attachments, messaging services,
  streaming
• Establish a Secure Authenticate Channel(SAC) with
  the receiving device
• Derivative Work Agents
• Extract and transform protected content or
  license into a different form
• Installation of DRM-protected software or data
• For fast execution, installed software and data
  is decrypted and this makes it vulnerable to
  copying
• Place the decrypted data into an
  access-controlled file system maintained by
  security agents

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OUR DRM SYSTEM - Security Agents

• Handle the security-related functions in DRM
  system
• Secure Memory and File management, Cryptographic
  operations, Key management
• Secure Memory and File management
• Access-controlled file system
• The storage of digital content that is no longer
  encrypted and a secure database
• Only trusted agents will be allowed to access
• Memory separation system
• Protect the memory being used by trusted agents
  from untrusted agent
• A memory separation manager configure a hardware
  monitor to define available memory area to task
• Secure memory system
• Protectes critical data that should never be
  allowed to leak out the system(e.g,. private
  keys)
• This memory is linked to tamper detection
  circuitry
• If suspicious events happen, this memory is
  immediately cleared

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OUR DRM SYSTEM - Security Agents

• Cryptographic Operations
• Symmetric key
• Protected content is encrypted using a
  symmetric-key algorithm such as AES
• Hash
• The binding between content and licenses is done
  with a hash algorithm such as SHA-1
• Public key(RSA, ECC)
• Content key encryption and decryption
• Digital signature verification and generation
• Secure networking protocols such as TLS or WTLS
• Key/certificate Manager
• Securely handle a database of the phones
  credentials(keys, certificates, IDs)
• Installation of credentials
• Updates or Removal of credentials
• Parse and verifying the certificates

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OUR DRM SYSTEM - DRM Credentials

• Serial and Model numbers
• Serial Numbers
• SN is a number that identifies the phone
• Rights can be enforced by matching SN in license
  and in
• device
• Model Numbers
• MN is a number that identified the hardware and
  soft
• ware version of a phone
• Content provider knows how to package the digital
  content for particular phones
• Root key
• Check the authenticity and integrity of the
  credentials of other devices, servers, or
  licences
• Private Keys and Certificates(Public key)
• KuPri and UniCert
• Used for establishing secure authenticate
  channel(SAC) to a phone
• KdPri and DRMCert
• Used for assigning content to a device
• Content encryption key is encrypted with KdPub in
  DRMCert and decrypted with KdPri

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SECURITY ISSUES

• License
• Hash value that links the license to the digital
  item
• The Rights allowed for that digital item
• A key to decrypt the digital item
• A signature of the license
• Integrity and Authenticity
• Verification of the license file signature
  (Public Key Infrastructure)
• A symmetric key is preprogrammed into each device
  or securely established(shared secret)
• Rights Enforcement
• DRM manager parse the license file and recognize
  the rights expression
• If a conflicting expression or one that cant be
  understood are found, it must fail in a secure
  manner
• Content Protection
• Content is protected with encryption up
• Streaming the content(decrypted) is protected
  via SAC
• Privacy Issues
• User information and identity in a license must
  not disclosed without the consent of the user

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FAMILY DOMAIN

• The consumers wish to used their content on any
  of their devices
• Some proposed DRM systems provide this with
  Public Key Infrastructure(PKI) and a centralized
  locker approach
• This is not suitable for devices such as mobile
  phone which may not have permanent networking
  capabilities
• FAMILY DOMAIN Approach
• Trusted Server referred to as a Domain
  Authority(DA) installs a domain private key in
  each of devices in a domain
• A Device needs to only register with a DA once
  and could access to all the content in a domain
  with domain private key

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EXAMPLE USE CASES
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Conclusion

• Our DRM framework is applicable to other devices
  such as PDA, set-top box, automobile, or a PC
• Content could be seamlessly shared amongst all
  devices through family domain
• There are many areas need to be complete before
  our DRM system becomes a reality
• Many use cases need to be explored
• The Software block need to be more thoroughly
  described
• Secure mechanism to extend the OS need to be
  developed
• Hardware support to enable a trusted computing
  platform needs to be deployed

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Thank you