Data security is crucial aspect in cloud storage. Providing security to a single file or to set of files is another important factor. In cloud, security is applied to a set of files i.e. to central location. In file sharing approach a single key can be used to gain access to storage. Applying security to each file in cloud is not possible with cloud environment. To solve this type of problems, new improved key assignment scheme have to be used. New improved algorithm that satisfies these conditions is summation key encryption. Summation key is of power more than two keys.