Digital Rights Management in a 3G Mobile Phone and Beyond

1. Digital Rights Management in a 3G Mobile Phone and Beyond Thomas S.Messerges, Ezzat A. Dabbish Motorola Labs Young Sub Ko

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

3. 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

4. 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 • Verify the hash of content • Decrypt the content and send it to the rendering software in the system

5. RI Cert Device Cert 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

6. 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 Device’s Public Key Rights Encryption Key (REK) and MAC Key Authentication, Non-Repudiation, and Integrity for RO (Including REK; Device RO) MAC of RO

7. DRM CONCEPTS AND STRATEGIES - Message Authentication Code(MAC)

8. OUR DRM SYSTEM - Interface for DRM • Two approach noted in Schneck’s 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

9. 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 device’s 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

10. 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

11. 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

12. 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 phone’s credentials(keys, certificates, IDs) • Installation of credentials • Updates or Removal of credentials • Parse and verifying the certificates

13. 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

14. 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 can’t 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

15. 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

16. EXAMPLE USE CASES Content Content License file License file

17. 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

18. Thank you