SDSM IN MOBILE CLOUD COMPUTING By- ID NO-1069 K.C. SHARMILAADEVI Sethu Institute Of Tech IV year-ECE Department CEC Batch: AUG 2012

Cloud computing is a general term for anything that involves delivering hosted services over the Internet. Among numerous benefits, cloud computing offers customers a more flexible way to obtain computation and storage resources on demand. Different from the general cloud computing concept, mobile cloud computing refers to an emerging infrastructure where both of the data storage and the data processing happen outside of the mobile device from which an application is launched.

SDSM, is a user-efficient and secure data service mechanism in mobile cloud computing, which enables the mobile users to enjoy a secure outsourced data services at a minimized security management overhead. The core idea of SDSM is that the mobile user can securely shift the data computing and distribution overhead to the cloud while the cloud has no idea about data content in the whole process. Additionally only authorized users can decrypt the cipher text while unauthorized users would learn nothing about the data.

Outsource encrypted file Access data on the cloud Data sharing Cloud server Cloud server Cloud server Cloud server Cloud server Cloud service provider SYSTEM MODEL

 To realize secrecy of data  Allows semi-trusted proxy to transform the data encrypted with user1’s public key into the one encrypted with user 2’s public key  Benefits : Strong access control Flexibility Low overhead

 PHASE 1 : Setup and KeyGen Algorithm System parameters and users secret key are built up We set the system master secret key msk = s Each mobile user registered in the system can obtain a private key corresponding to his identity, sk = H1(ID) s is used in the process of user registration

 PHASE 2 : Data Encryption The data F is divided in to n fractions F =(m1,m2, ……, m n ) Each part m i is undergone encryption process Encrypted data is M i = (g, m.e(g, H 1 ( ID) )) After encryption, the user uploads F’ = (M1, M2,.., Mn)  PHASE 3 : Data Sharing RkGen Algorithm Generates proxy key rk = (H1(ID A ), IBE ID B (X)) The cloud can deploy the re-encrypt key rk to permit the authorized user to get the cipher text decrypted with his own secret key.

PHASE 4 : Access Data Sharer sends request to cloud server Cloud checks for the validity of sharer If re-encryption key exists for the sharer, Cipher text is achieved by RkGen algorithm Sharer fetches the data and runs the decrypt algorithm on M i to obtain m i Thus entire file is obtained F=(m1,m2,..,m n ) PHASE 5 : Policy Updating For updating the list of sharers the user has to update re-encryption keys instead of decrypting the cipher text from cloud

Running time is denoted by operate(m i ) If n is the number of blocks, then time for whole operation is n.operate(m i ) n is determined by size of the file F Delay could be reduced in practice since each file needs to be pre-processed only once To achieve the access control of file F, data owner only requires forwarding a re-encryption key of a small size 2q (q << F) instead of the ciphertext of F Cost is reduced