ASYMMETRIC UPDATABLE ENCRYPTION USING ELGAMAL FOR INFINITE CIPHERTEXT REVISIONS

Abstract

This paper presents an ElGamal-based asymmetric updatable encryption scheme designed to tackle the challenges associated with secure key rotation in cryptographic systems. The proposed method allows ciphertexts encrypted under a previous key to be securely and efficiently transitioned to a new key without the need for decryption, thereby preserving data confidentiality and integrity. By exploiting the mathematical characteristics inherent in ElGamal encryption, the scheme supports unlimited key update iterations, asymmetric encryption functionality, and is independent of specific ciphertext formats. Lightweight pseudorandom generators (PRGs) are employed to ensure secure and efficient handling of the random values necessary during encryption and re-encryption operations. The approach guarantees strong forward and backward security, protecting against data leakage even if keys are compromised. Extensive performance assessments demonstrate its efficiency, showing minimal computational and communication overhead, making it wellsuited for both large-scale infrastructures and environments with limited resources. Additionally, comparative studies confirm its advantages over existing methods in terms of encryption speed, ciphertext update duration, and scalability. Overall, this work offers a practical and secure solution for frequent key management across various applications, including cloud storage, Internet of Things (IoT) devices, and secure communication networks.