Field Programmable Gate Arrays (FPGAs) are widely adopted in datacenters, where each FPGA is exclusively assigned to a task. This strategy results in significant resource waste and increased task rejections. To address this issue, placement algorithms adjust the locations and shapes of tasks based on Dynamic Partial Reconfiguration, which partitions an FPGA into multiple rectangular areas for sharing. However, existing schemes are designed for static task sets without adjustable shapes, incapable of optimizing the placement problem in datacenters. In this paper, FEditor is proposed as the first consecutive task placement scheme with adjustable shapes. It expands the planar FPGA models into three-dimensional ones with timestamps to accommodate consecutive tasks. To reduce the complexity of three-dimensional resource management,State Frames(SFs) are designed to compress the models losslessly. Three metrics and a nested heuristic algorithm are used for task placement. Experimental results demonstrate that FEditor has improved resource utilization by at least$19.8\%$and acceptance rate by at least$10\%$compared to the referenced algorithms.SFsand the nested algorithm accelerate the task placement by up to$10.26\times$. The suitability of FEditor in datacenter environments is verified by its time efficiency trends.

Attribute-based encryption (ABE) has been a preferred encryption technology to solve the problems of data protection and access control, especially when the cloud storage is provided by third-party service providers. ABE can put data access under control at each data item level. However, ABE schemes have practical limitations on dynamic attribute revocation. We propose a generic attribute revocation system for ABE with user privacy protection. The attribute revocation ABE (AR-ABE) system can work with any type of ABE scheme to dynamically revoke any number of attributes.

Cloud-based storage is a service model for businesses and individual users that involves paid or free storage resources. This service model enables on-demand storage capacity and management to users anywhere via the Internet. Because most cloud storage is provided by third-party service providers, the trust required for the cloud storage providers and the shared multi-tenant environment present special challenges for data protection and access control. Attribute-based encryption (ABE) not only protects data secrecy, but also has ciphertexts or decryption keys associated with fine-grained access policies that are automatically enforced during the decryption process. This enforcement puts data access under control at each data item level. However, ABE schemes have practical limitations on dynamic user revocation. In this paper, we propose two generic user revocation systems for ABE with user privacy protection, user revocation via ciphertext re-encryption (UR-CRE) and user revocation via cloud storage providers (UR-CSP), which work with any type of ABE scheme to dynamically revoke users.

Cloud computing provides elastic, on-demand, self-provisioning computing resources to users. Highly dynamic and heterogeneous environments present significant challenges to access control. Attribute-based signature (ABS) enables fine grained access control over an expressive access policy (predicate). However, user revocation, especially anonymous user revocation, is not straightforward to provide for existing ABS schemes. In this paper we propose an anonymous revocation feature for an ABS scheme that is practical to deploy in a cloud environment.

Cloud storage provides the potential for on-demand massive data storage, but its highly dynamic and heterogeneous environment presents significant data protection challenges. Ciphertext-policy attribute-based encryption (CP-ABE) enables fine-grained access control. However, important issues such as efficient user revocation and key refreshing are not straightforward, which constrains the adoption of CP-ABE in cloud storage systems. In this paper we propose a dynamic user revocation and key refreshing model for CP-ABE schemes. A key feature of our model is its generic possibility in general CP-ABE schemes to refresh the system keys or remove the access from a user without issuing new keys to other users or re-encrypting existing ciphertexts. Our model is efficient and suitable for application in cloud storage environments. As an example, we use BSW's CP-ABE scheme to show the adaptation of our model to a CP-ABE scheme.