Design of ElGamal PKC for encryption of large messages

ElGamal technique being a popular public-key cryptosystem used for message confidentiality, authentication/signature and many others. However, the application of the same for the confidentiality of comparatively large messages require repetitive ElGamal operations and thereby increasing the computation cost with reduction of the security protection. Similar to other recent proposals, we also proposed a generic variation of the original ElGamal cryptosystem for encrypting large messages with minimum-possible increasing of the secret keys. In fact, we developed a technique for reusing of the same secret; however, the final encryption/decryption key for each message-component is different. Thus, for n secret keys, total 2n number of messages to be encrypted in our proposed scheme. Also, we include sub-message sequence number so that the correct message ordering and some security protections against replay attack, message-drop, message integrity etc can be checked at the destination-end. The proposed ElGamal variants through comparison with other relevant techniques show that it enhances overall performance without compromising the security protection.