Improved ElGamal Cryptosystem for Secure Data Transfer in IoT Networks

ElGamal cryptosystem possess many technical challenges such as encryption of large messages, integrity and authentication of data, non-malleability, semantic security etc. This paper proposes an efficient ElGamal based public-key cryptosystem (PKEIE) to achieve the encryption of large messages along with confidentiality, integrity and authentication. The algorithm is built on DDH assumption (Decisional Diffie- Hellman assumption) which is quite hard to break. Apart from the normal key generation, it uses a secret key for the secured hash function to provide integrity and authentication. The algorithm is capable enough to encrypt data of any size which is not possible with the ElGamal cryptosystem. The message to be encrypted is split into blocks of equal size and each block is assigned with a block index. The block indexing makes the scheme a probabilistic one. The algorithm holds semantic security because it is built on the DDH assumption. It assures non-malleability against attacks. The algorithm is compared with the ElGamal variant schemes based on the attained level of security and throughput and suitable for IoT networks by in cooperating integrity, authentication and encryption using a single algorithm.