Modified Elgamal Cryptosystem Algorithm (MECA)

Abstract

In 1985 a powerful and public-key scheme was produced by ElGamal. ElGamal encryption/decryption algorithm is based on the difficulty of discrete logarithm problem where it is straight forward to raise numbers to large powers but it is much harder to do the inverse computation of the discrete logarithm. Now, there are so many algorithms available which can solve the discrete logarithm problem of small size numbers in a reasonable time. So to improve security, we proposed a Modified ElGamal Cryptosystem Algorithm (MECA) to enhance the security for encrypting long messages and also secure against mathematical and brute-force attack as well as Low-Modulus and Known-Plaintext attack on Elgamal. The security of this algorithm is based on the difficulty of solving the discrete logarithm problem and Integer factorization problem. This paper also presents comparison between MECA and ElGamal cryptosystem in respect of security and complexity.