Cryptography is an art of secret writing. To ensure data security in both data transfer and data storage cryptographic techniques are used for the data we handle in our day to day activities. The need for cryptographic techniques exists from the period of 150 B.C. till date. Though there are too many cryptographic algorithms, an algorithm with reduced complexity and utmost security is needed. And so, DNA cryptography paves a way towards satisfying the needs with its own biological properties. DNA has greater capacity to store, process and secure data. The existing DNA cryptographic algorithm does not have a standardized approach that involves both biological and arithmetic processes. To meet out the standardized framework we propose a novel DNA based cryptosystem comprising key generation, encoding, and encryption, decryption methodologies. The detailed performance and security analysis with their results are shown to support the strength of our algorithm towards reducing the computational complexity as well as the storage complexity and thereby achieving an enhanced security.