In cloud computing, the user transfers their burden of installing the software, data maintenance, infrastructure, storage space etc. on the cloud service provider. These providers offer to their clients the possibility to store, retrieve and share data with other users in a transparent way[1]. In this paper, a method is implemented for ensuring the data security of the files being uploaded to the cloud by different clients. This security is achieved through a technique of encryption using Blowfish with MD5 method. The results of the proposed method have shown that the size of the encrypted file is decreased as compared to that of existing techniques. So, the storage space of the cloud is used in a much efficient manner when the proposed technique is implemented. Moreover, the replay attack is also defended more efficiently through the proposed method thus increasing the security level of the cloud.With the use of MD5 method along with blowfish, the data is encrypted in lesser time hence making it difficult for the attacker to hack the data, of the client, which is uploaded on the cloud.