The document presents a secure data sharing scheme for dynamic groups in the cloud, addressing the challenges of data sharing in untrusted environments, particularly in the presence of collusion attacks. It proposes a method for secure key distribution without requiring secure communication channels, allowing users to obtain private keys from a group manager, while ensuring fine-grained access control and efficient user revocation. The advantages of the proposed system include low computation costs that remain consistent regardless of the number of revoked users, making it suitable for dynamic group scenarios.