Dynamic and Revocable Multi File-Multi User Access Control based Aggregate Key Cryptosystem to Secure Data Sharing in Cloud Computing

The emergence of cloud computing and IoT has made effective and secure cryptographic schemes essential for sharing data online. To protect sensitive data, data owners must encrypt files before storing them online and grant decryption rights to authorized users. A novel approach, the Key Aggregate Cryptosystem (KAC), enables users to decode multiple pieces of data types with one single constant key size, enhancing efficiency. In this article the Efficient Revocable & Dynamic Secure Aggregate Key Cryptosystem Approach (ERDSAKCA) is tailored for cloud environments. This innovative strategy not only simplifies the key management through KAC but also allows for dynamic user revocation by updating the ciphertext, ensuring revoked users cannot access new data while non-revoked users retain access without updating their private keys. The scheme also incorporates a verification mechanism to ensure accuracy in user revocation and ciphertext updates. Compared to existing schemes, ERDSAKCA effectively manages user access control and user revocation and reduces the costs associated with key management and storage. Lastly, the scheme is shown to be selectively chosen plaintext-safe under the conventional model, offering strong protection against cryptographic attacks.