The Cloud Computing Paradigm simplified the IT infrastructure management thereby making the organiza-tions and enterprises to rapidly migrate from conventional model to service driven model. The service driven model allows the users to access, maintain and backup the files from remote location over the internet through the central-ized cloud service providers. Inspite of major advantages, there are some concerns for the safety and privacy risks of organizational and users sensitive information in cloud stor-age. The existing service oriented model uses distributed key management which encrypts the data and stores it in cloud servers to provide the authentication to data, but it addresses challenges in identifying ownership of data, boot-strapping problem and securing the keys. The proposed system uses block chain, a distributed ledger for user authentication in cloud server and Hash graph with asynchronous byzantine fault tolerance algorithm is proposed for replicat-ed state machines with guaranteed Byzantine fault-tolerance and it can be utilized in the IT Infrastructure envi-ronment which solves the hassles of maintaining security keys