Cloud computing is one of the best methods for supplying flexible, scalable, and on-demand computing power and subsystems. The cloud model is particularly useful in fulfilling the projection requirements for the upcoming years because computing resources such as storage and infrastructure are presented as services available on the Internet. This model shifts the responsibility of maintaining the bare resources to users and organizations, allowing them to be charged only for what they consume. Even though it offers immense opportunities to respond to the changing business environment, cloud computing poses significant security challenges on data security and privacy, data integrity and efficiency, reliability, and many others. Common measures of security such as encryption and access control are often used. In this paper, the focus is on how blockchain technology can be applied to cloud computing to increase its security in terms of providing data integrity, authentication, and accountability in the cloud.