Unbounded Depth ElGamal-Based Asymmetric Updatable Encryption Technique

This article introduces an ElGamal-based asymmetric updatable encryption scheme, tailored to address the challenges of secure key rotation in cryptographic systems. The proposed solution enables ciphertexts encrypted under an old key to be efficiently and securely updated to a new key without decryption, ensuring data confidentiality and integrity. By leveraging ElGamal's inherent mathematical properties, the scheme provides unbounded depth for key updates, asymmetric encryption capabilities, and independence from specific ciphertext structures. Lightweight pseudorandom generators (PRGs) are used to facilitate secure and efficient management of the random values required for encryption and re-encryption processes. The proposed approach demonstrates robust forward and backward security, ensuring resilience against information leakage even in the event of key compromise. Comprehensive performance evaluations highlight its efficiency, with minimal computational and communication overhead, making it suitable for large-scale systems and resource-constrained environments. Comparative analysis further confirms its superiority over existing techniques in encryption speed, ciphertext update time, and scalability. This work provides a practical and secure framework for managing frequent key updates in diverse applications, including cloud storage, the Internet of Things, and secure communication networks.