Technology On Attribute-Based Encryption In Cloud Computing

Google launched the Google 101 program and formally proposed the concept of cloud in 2006, which brings out another new technology revolution. Since then cloud computing has been a hot research topic in the literature. In the cloud environment, users can access the resources in the cloud server and enjoy the convenience of cloud services. Cloud computing can provide powerful computing and storage resources to reduce the cloud users' burden and save the local computing resources. Data stored in the cloud server can achieve data information sharing, but it will bring some security issues, such as unathorized access to the data stored on the cloud, as well as the privacy problem of the stored data. Attribute-based encryption(ABE) achieves fine-grained access control of user's data and solves the above problems to a certain extent. Ciphertext policy attribute-based encryption mechanisms mostly use a single authority center to manage and distribute the user's key, and requires that the authority center is fully trusted. Hence, this requirements makes ABE hardly meet the needs of distributed data storage in cloud computing environment.This dissertation compares the existing attribute-based encryption schemes with emphasis on the advantages and disadvantages, and elaborates on the drawbacks with respect to the computational overhead and the practicality. The main contributions of the dissertation are summarized as follows.1. Based on the honest but curious server model, we propose a multi-authority outsourcing attribute-based encryption access control model in the cloud computing paradigm. In the model, the user can reduce the computational burden by outsourcing a part of the calculations to the cloud service provider. Furthermore, the model introduces multi-authority to manage and distribute secret keys, which renders it more suitable for the application of distributed data storage in the cloud. Finally, we prove that the system can achieve access control security, defend collusion attacks, and gain the multi-authority security goal.2. Based on the attribute-based encryption scheme, a new type of attribute-based encryption scheme is proposed. In the new scheme, the ciphertext size and the encryption time is in a direct proportion to the number of attributes. It is proved that the scheme is secure in the random oracle model under the standard intractability assumption of decisional bilinear Diffie-Hellman problem.