Security is necessary for performing the effective data communications in internet and cloud environment. The data security in cloud is becoming very challenging task due to the presence of huge volume of cloud users. Even though, the various secured cloud data storage mechanisms are available and tried to fulfill the current requirement in terms of security level and efficiency. However, the available works are not obtained the enough security level and the efficiency while storing and sharing the data in cloud. For this purpose, this work proposes a new secured storage method for providing data security to store the data securely in cloud. The proposed system consists of three different algorithms for performing prime number generation, digital signature creation for generating keys, encryption, decryption and authorization. Here, a new technique to find a co-prime number which is used to generate keys in key generation process and also useful for performing encryption and decryption process. Moreover, a new key generation technique is also introduced for elliptic curve cryptography and digital signature algorithm using polynomial congruence for performing key generation process securely. In addition, a new elliptic curve and polynomial congruence based encryption/decryption algorithms for performing data encryption and decryption in the process of data storage and communication. Finally, the user authenticity is verified by the proposed digital signature algorithm in this work. The experiments have been conducted for evaluating the proposed secured storage and communication system and proved as better than others in terms of efficiency and security level.