Phosphor A Cloud based DRM Scheme with Sim Card

2010 12th International Asia-Pacific Web Conference

Author : Peng Zou, Chaokun Wang, Zhang Liu, Dalei Bao

OutlineDigital Right Management(DRM)

– Traditional Access control/Cryptography model

– DRM solutions

– Typical DRM ModelPhosphor A Cloud based DRM Scheme with Sim Card

– Introduction

– Differences between sim card and smart card

– Actor

– Notations

– License State Word

– Phase

– Security Analysis

– Cloud of Phosphor’s Backend

– Conclusions

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Traditional Access control/Cryptography model

Trusted Zone

authorized user

unauthorized user

Data authorized center

Traditional Access control/Cryptography model

Trusted Zone

unauthorized user

Data authorized center

authorized user

unauthorized user

authorized user

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DRM solutions

Trusted Zone

authorized user

unauthorized user

Data authorized center

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Typical DRM Model

Content Provider

Client

Content Distributors

License Server

Four kinds of roles in the DRM.

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Typical DRM Model

Content Provider

Client

Content Distributors

License Server

Content Provider

1.2 the usage rights

is specified

1.3 the content is encrypted

by using content key and

then packed

1.4 content package is send to

Content Distributors. But

content key is not send to

Content Distributors

1

1.1 the content and content

key are generated

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Typical DRM Model

Content Provider

Client

Content Distributors

License Server

Content Provider

2.1 the usage rights and content

key are delivered to License

Server, because License

Server is trusted.

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Typical DRM Model

Content Provider

Client

Content Distributors

License Server

3.1 The user purchases legal

content package from

Content Distributor

Content Distributors

3

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Typical DRM Model

Content Provider

Client

Content Distributors

4.1 The user had paid for

content.

License ServerLicense Server

Purchase Proof

4

4.2 The corresponding usage

rights and content key should

be securely send to the Client.

4.3 License Server generate

appropriate License

for the Client.

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Typical DRM Model

Content Provider

Client

Content Distributors

ClientLicense Server

5.1 Usage rights and content

key form License

+

5.2 the protected content is

decrypted by content key

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Phosphor A Cloud based DRM Scheme with Sim Card

Introduction

• Fewer works pay attention to data management issues for the DRM backend (servers), which are extremely important for the efficiency of a DRM system when the number of users scales up.

• The cloud based DRM with an efficient unstructured data management service can satisfy performance requirements with high elasticity and low cost.

• Smart card follows the Standard ISO7816 which defines the physical and electrical characteristics of smart card.

• Sim card is produced according to the Specification GSM11.11 and GSM 11.14 besides Standard ISO7816.

•

• All these characteristics make sim card a more efficient, secure platform than normal smart card.

Differences between sim card and smart card

GSM11.11 GSM 11.14

Actor

Content Provider Content Server License Server

Sim CardDRM AgentUser(Client)

NotationsNotation Decription

Ki

a secret key stored in the hardware of sim card. In our scheme, its copy is also stored in the storage of license service.

A8(.)the algorithm for generating Kc. Kc is the cryptographic key used by A5. The inputs are K i and a random number.

A5(.)the algorithm for enciphering/ deciphering data. The inputs are Kc and data.

Kcekthe key by which content service encrypts the digitalcontent.

UK the key by which license server encrypts Kcek.

Auk(.) the algorithm for generating algorithm UK.

Ek(.) a symmetric encryption algorithm by key k.

Dek(.) a symmetric decryption algorithm by key k.

H(.) a public one-way hash function.

|| concatenation operation.

License State Word

• Propose a data structure License State Word (LSW)– Stored in the sim card file system.– LSW = (License_ID||Rand||License_Hash)

• The LSW protocol – Designed for privacy and security on the basis of APDU

command.– The instructions of the ADPU command for LSW are

CREATE_LSW, UPDATE_LSW,DELETE_LSW and GENERATE_UK.

• We apply data hiding technology proposed in [11] on the LSW to make sure that the LSW is invisible.

Preparation Phase

Content Provider Content Server

License Server

(1) (2)

(3)

(4)

(1)Upload contents by SSL

(2)Generate Kcek , Encryption the content by Kcek using Symmetric encryption

(3)EPKls(content_id || Kcek || Icontent_id)

(4)License Server stores the content_id, Kcek, Icontnet_id

(5)Transmit content_id , url

(5)

User(Client)

Right Customization Phase

DRM Agent

Content Server

User(Client)License Server

(1)Check Content_id existed? Case Y : Check LSW and Play Case N : Go to (2)

(2)Request for url

(3)Transmit the url

(4)Link url to custom the right

(5)DRM Agent received TI = { content_id, License_ID, right }

Content Provider

(1)

(3)(2)

(4)

(5)

License Acquisition Phase

License Server

Sim CardDRM Agent

(1)Generate Random number Rand

(2)Pass Rand to Sim Card for Kc=A8(Ki,Rand) and CK=A5(Kc,Rand) ※CK is for the sim card authentication

(3)Combine Rand,IMSI,CK ※IMSI is 國際移動用戶識別碼

(4)CK* calculate by the same method using IMSI and Rand. Check CK*=CK? UK=Auk(Rand || Kc) EK=EUK(Kcek)

(5)Create license={License_ID, right, EK, Rand, H(Right||EK||Rand)}

(6)LSW=(License_ID||Rand||License _Hash)

Content Provider Content Server

User(Client)

(1) (2)

(3)

(4)

(5)

(6)

Play Pahse

DRM Agent Sim Card

(1)Check Hash with LSW in sim card ※H(Right||EK||Rand)} = license_Hash?

(2)If equal, send Rand and License_ID

(3)Generate UK

(4)Transmit UK

(5)Kcek=DEUK(EK) Content=DEKcek(Content) Store Kcek and Content in the device secure memory

(6)If user stop, Kcek and Content will be deleted

(1)(2) (3)

(4)

User(Client)

(5)

(6)

Download Phase

(1)Insert sim card to another device

(2)Download license according to LSW

(3)Check new license against LSW in sim card If verification fail, deleted new license

DRM AgentLicense Server

User(Client)

(3)

(1)

(2)

Security Analysis

• Phosphor’s security is based on the sim card and LSW. The data hiding approach applied on the sim card file system makes LSW invisible. The interaction between sim card and DRM Agent has been protected by the LSW protocol designed based on APDU command. The algorithms used in sim card are covert by the mobile operator.The authentication between sim card and License Server protects Phosphor from imposter attacks.

Cloud of Phosphor’s Backend

Phosphor is a cloud based DRM scheme whose backend is based on Cloud Computing.It inherits advantages of cloud computing such as low cost and high elasticity. Phosphor’s backend consists of two parts. One is the logic implementation cloud and the other is the unstructured data management system (USDMS) cloud as shown in Fig.1.

Implementation

Conclusions

• LSW is used to ensure the license’s integrity,by which Phosphor can protect licenses from being abused and illegally modified. Phosphor has great many advantages such as the physical and logical protection of the sim card,the secure protocols as well as the Cloud Computing with unstructured data management system applying on the Phosphor’s backend. All these characteristics make Phosphor a more secure, efficient, stable Mobile DRM scheme, especially for the mobile operator.