Abstract: Symmetric key and asymmetric keys are used to encrypt and decrypt data, in order to accomplish the main idea of security i.e. to maintain integrity and give valid authentication. Information security and the guaranteed exchange of secure information is effectively achieved through cryptographic techniques. In cloud computing it is necessary to secure data transmission from sender to receiver from hacking, for that we make use of the effective service called the EC2, which is provided by Amazon web services. This allows us to compute in a scalable way in the Amazon cloud. S3, which is known as the simple storage security service is used to store data at any instant in any place. We proposed to develop a modified RSA algorithm to generate a pair key and digital signature to authenticate message. This paper mainly focuses on maintaining confidentiality between cloud and its users in addition to preventing it from attackers.