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.