Security is one of the biggest concerns in the developing world. It is important to ensure a safe transfer of information between communicating parties, protecting them from attacks. Many standards and developed encryption protocols are available as resources and are used based on the requirements. In this thesis, we propose a customized encryption algorithm and an authentication scheme to safely transfer information. The algorithm is a variation of Advanced Encryption Standard (AES) and is

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... ied out between multiple devices. AES uses only one private key (symmetric key) to encrypt the data. The implementation works on a single standard irreducible polynomial of degree '8' which is further used to compute multiplicative inverse tables, S-boxes and inverse S-Boxes required for the working of every layer in the algorithm. As compared to AES, we use sixteen irreducible polynomials of degree '8' instead of one in our implementation. Key sizes for AES are usually 128, 192 and 256 bits in size; we use a 128-bit key. Unlike symmetric encryption, asymmetric encryption uses two keys, private and public keys. The public keys are shared among the communicating parties, while the private keys are kept secret. The keys are supposed to be large in size to maintain strength. Thus, they usually range from 512 bits to 2048 bits or more for asymmetric cryptography. The communicating parties can start with public-private keys and agree upon a common key (session key) which can iii be used as a key to AES. Diffie-Hellman key exchange protocol uses a combination of AES and RSA algorithms resulting in reliable cryptosystems. Our algorithm focuses on devising a new protocol for key establishment and agreement, using the combination framework. The implementation of the communication protocol between two devices, with a prospect of working with multiple devices using a centralized server, is presented. The outcome is to establish a different approach towards encryption and enhance security by providing protection against Man-in-the-Middle attacks. The customized algorithms are implemented using Python. iv To my family and friends for their love, endless support and encouragement.