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Utilizing cloud computing, users can avail a compelling and effective approach for information sharing between collective individuals in the cloud with the facility of less administration cost and little maintenance. Security in cloud computing refers to procedures, standards and processes created to provide assurance for security of information in the cloud environment. In this paper, we project a secure data sharing method in cloud for dynamic members by producing keys for users using Logic Key Hierarchy (LKH) model, i.e., a tree-based key generation technique. We have generated this key using reverse hashing and one way hash-based technique so that no exiled user can predict the new key and new users cannot predict the old keys of the network group. From numerous experiments, this work is proved to be the best in maintaining forward secrecy, backward secrecy and group compromise attacks and consumes less computation cost compared to any other hash-based key generation techniques.

In embedded multicore shared memory systems, processing elements (PEs) are mutually untrusted since they carry different computing tasks independently. Therefore, the sharing of secret constants (SCs) between PEs, which is applied in the existing confidentiality protection schemes, will lead to the leakage of nonshared data. Besides, for integrity protection, tree construction checking over the whole counter space leads to the increase of both memory occupation and the average delay of verification. In this paper, we propose a ciphertext sharing confidentiality protection scheme based on certificateless proxy re-encryption and an integrity protection scheme based on a multigranularity scalable hash tree for secure data sharing between untrusted processing elements (SDSUP). With our schemes, the SC does not need to be shared and the scale of the checking tree is reduced, thus solving the leakage of nonshared data and reducing the high cost in integrity check. The results from the Rice Simulator for ILP Multiprocessors (RSIM) multicore simulator show that compared with the unprotected system, the performance degradation from applying the confidentiality protection scheme is 17.3% on average. Moreover, the performance degradation of the integrity protection scheme is 12.89%, which is superior to 35.36% for the bonsai Merkle tree (BMT), 29.49% for the multigrained hash tree (MGT) and 21.82% for the multigranularity incremental hash tree (MIT).