Privacy and accountability in cloud computation and storage

Abstract

newline Cloud computing is a cost-effective computing paradigm for convenient, ondemand data access to a shared pool of configurable computing resources such as networks, servers, storage, applications, and services. While providing payper-use on-demand service to the service consumer, the cloud service provider should minimize computation error on data stored in a cloud storage server. If there is any error, one can recompute or restore the data, but a user cannot detect an error. There have been some approaches like verifiable computation, secure computation, and multi-party computation, which may find a useful application in cloud storage/computation services; however, most of these approaches assume that the computation s logic on data is public. The problem becomes challenging when the logic of computation is hidden to clients. In this thesis, the notion of Private Polynomial Evaluation (PPE) is defined along with a new security model indistinguishability against chosen function attackquot (IND-CFA), where an adversary tries to guess which polynomial is used among two polynomials of his/her choice. The existing schemes on verifiable computation with hidden polynomial are not IND-CFA secure. The proposed scheme, Private IND-CFA Polynomial Evaluation (PIPE), is the first IND-CFA secure PPE. It is IND-CFA secure under the decisional Diffie-Hellman (DDH) assumption in the random oracle model. newline newlineIn a public cloud system, the cloud requires to verify a user s identity before providing any service. Depending on the nature of applications, the cloud server s computation may require to preserve the user s identity from the cloud. For example, in healthcare applications, it is advisable to preserve the privacy of users and the privacy of the data. Another proposed scheme Verifiable Obvious IND-CFA Polynomial Evaluation scheme (VIP-POPE), in which the server computes over encrypted data, and provides proof of computation, preserve the privacy of the user s data. The proposed scheme VIP-POPE preserves the user s ...