Digital Rights Management in a 3G Mobile Phone and

Beyond

Thomas S. Messerges, Ezzat A. DabbishMotorola Labs

Shin Seung Uk

Introduction DRM Concepts and Strategies Our DRM System

◦ DRM Manager◦ Trusted Application Agents◦ Security Agent◦ DRM Credential

Security Issues Family Domain Example Use Cases Conclusion

Contents

3G mobile phone◦ High communication rates

144K ~ 2Mbps◦ Personal Area Networking capability

P2P sharing of digital item over short-range networks◦ High Internet Connectivity

Losses from piracy

Digital Rights Management(DRM) will be an important component for future Mobile phone

Introduction

License File◦ Metadata◦ Usage Rules◦ Encrypted Key◦ Hash◦ Signature

Protected Content File◦ Encrypted Content

With key in license file

DRM System◦ Rendering Software◦ DRM Services

DRM Concepts and Strategies- Overview of trusted DRM System

DRM Concepts and Strategies- Open Mobile Alliance DRM

DRM Concepts and Strategies- Open Mobile Alliance DRM

MAC of RO

Protected RO

RO

Rights

Content Encryption Key (CEK)

Permission

Digest of Content

Content ID

Digital Signature of Rights (optional)

Right Encryption Key (REK) and MAC Key

Decr

ypt

How to interface the DRM and security S/W with the phone’s OS and applications◦ Two approaches of Schneck’s paper

Replace the I/O elements of OS with new modules Hyperadvisor

Our approach◦ The OS is extended to support DRM functionality◦ Access these extended system services through API

Our DRM System

Authenticate Licenses and Content◦ Before use protected digital content◦ Need to verify the integrity and

authenticity of the license file Computation of hash in the license file Verifying the signature of the license

Enforce Rights◦ Application can ask the DRM manager

To do Actions like Play, display, copy Actions can be associated with

3 fundamental types of rights Render rights, Transport rights, Derivative work rights

◦ Some additional events Need to use a secure database to track events

◦ Rights to an action are assigned to a device

Decrypt Content

Our DRM System- DRM Manager

Access and manipulate decrypted content

Rendering Agents◦ Provide application to render

the protected content◦ Provide the low-level driver

Convert the digital data◦ The execution of a DRM-protected software

application is categorized as a rendering operation

Transport Agents◦ Provide services that move content from one location to another◦ The establishment of a Secure Authenticated Channel(SAC) with help of security

agent

Derivative Work Agents◦ Used to extract and transform protected content into a different form◦ Installation of DRM-protected software or data

Our DRM System- Trusted Application Agents

Memory and file management◦ Access-controlled file system

Store decrypted digital content Store a secure database

Encrypted private keys and data

◦ Memory separation system Configure a hardware monitor to define

available memory area to task◦ Secure memory system

Prevent critical data from leaking out of the system Linked to tamper detection circuitry

Cryptographic operations◦ Symmetric key◦ Hash◦ Public key

Key/Certificate manager◦ Securely handling a database of the phone’s credentials (keys, certificates, ID)

Our DRM System- Security Agents

Serial number◦ Unchangeable number

that identifies the phone

Model number◦ Number that identifies

HW and SW version

Root key◦ Check the authenticity and

integrity of the credentials

Private keys and Certificates◦ 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 and decrypted with KdPri

Our DRM System- DRM Credentials

License◦ Four essential items

A 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◦ Established through a Public-Key Infrastructure(PKI) or a shared secret

Rights Enforcement◦ DRM manager needs to parse the license file and recognize rights expressions◦ DRM manager needs to be able to recognize the version of the license file

Content Protection

Privacy Issues◦ User information and identity in a license must not disclosed without the consent of

the user

Security Issues

Consumers wish to user content on any of their devices

Suitable for devices with limited or no networking ca-pability◦ Device only needs to register with DA once and can access to

all the content in a domain with domain private key

Family Domain

Example Use Cases

Our proposed DRM framework is also appli-cable to other devices◦ PDA, set-top box, automobile, or a PC

Family domain concepts could be make con-tent be more seamlessly shared amongst all devices

Conclusion