OUTLINE
    Introduction
    What This Paper Present
    Models And Assumptions
    Proposed Scheme
    Complexity 
    Summary 
            INTRODUCTION
    Cloud computing allow users to remotely storage their data and utilize the 
    could application without need to local hardware and software management. 
    The resources of the computing infrastructure are provided as services over the 
    Internet.
    Saving money, instead of paying their own storage, users can use cloud for 
    their business. Amazon provide unlimited storage for about $60 per years.
    Cloud users are content (data) providers. 
    Users publish data on cloud servers for sharing.
    Users  need  fine-grained  data  access  control  in  terms  of  which  user  (data 
    consumer) has the access privilege to which types of data.
                 CLOUD
    Challenging :data security and access control when users outsource sensitive 
     data for sharing on cloud servers.
    Introduce a heavy computation overhead on the data owner for key distribution 
     and data management when fine-grained data access control is desired.
    In the traditional access control, data owner and servers are in the same trusted 
     domain, where the servers are fully entrusted.
    This assumption no longer holds in cloud computing because data owner and 
     cloud servers are very usually in different domains. 
    Also cloud servers are not allowed to access the outsourced data content for 
     data confidentiality
    At same time, the data resources are not physically under the full control of the 
     owner.
                CLOUD
    
     Fine-grained  access  control  of  data  stored  on  untrusted  cloud 
    servers
    encrypting data and give decryption keys only to authorized users. 
    Unauthorized users, including cloud servers, they do not have the key.
    
     This introduce a high complexity on key management and data 
    encryption.
  NOTATION