Time-Sensitive Networking (TSN) enables deterministic transmission of Scheduled Traffic (ST) through mechanisms such as the Time-Aware Shaper (TAS) and Cyclic Queuing and Forwarding (CQF). However, both rely on high-precision global clock synchronization and adopt a per-class queuing paradigm, making them susceptible to clock synchronization errors. Asynchronous Traffic Shaping (ATS) ensures bounded delay without requiring global time synchronization by assigning an eligibility time to each flow during per-flow shaping, yet often exhibits larger delay jitter. In this paper, we propose a novel scheduling paradigm for TSN by introducing per-flow queues and present the Per-Flow Hierarchical Scheduling (PFHS) mechanism. PFHS divides a hyperperiod into equal-length time slots, which are then assigned to different levels. ST flows are also assigned to these levels, and each flow is scheduled to transmit using only the time slots assigned to its level. By partitioning the bandwidth among distinct ST flows’ per-flow queues in this hierarchical manner, PFHS achieves fine-grained bandwidth allocation. We conduct a theoretical worst-case delay analysis of PFHS, demonstrating its capability to ensure deterministic transmission and tolerate bounded clock synchronization errors. We evaluate the performance of PFHS across various scenarios by extensive simulations on the OMNeT++ platform. Experimental results show that PFHS guarantees the end-to-end delay of ST flows. Moreover, the proposed hierarchical division algorithm successfully schedules 93% of 1000 flows.

Deterministic delivery of scheduled traffic (ST) is critical in time-sensitive networking (TSN). The time-aware shaper (TAS) defined by IEEE 802.1Qbv is the enabler to ensure deterministic end-to-end delays of ST flows. However, TAS does not consider the emergency sporadic flows that commonly exist in automotive and industrial control applications. Therefore, TAS cannot resist the interference of emergency sporadic traffic on normal scheduled traffic. In this paper, we improve the TAS’s time slot allocation and queue occupancy rule and propose a combined scheduling strategy composed of dynamic local regulation and static global planning. Dynamic local regulation executes the earliest deadline first (EDF) discipline at switching nodes to adjust ST frames’ transmission dynamically. Static global planning calculates the offset of ST flows at the source and guarantees bounded delay and jitter. Furthermore, we formalize the offset optimizing problem with considering the EDF, delay, and jitter constraints. Finally, we implement our prototype on OMNet++ 6.0.1. Simulation results further demonstrate that the combined strategy has bounded latency and jitter in the presence of emergency sporadic flows. Besides, the comparison experiments show that our design is superior to eTAS in terms of the jitter and end-to-end delay.

Time-sensitive networking (TSN) is widely used in industrial automation and automotive applications due to its ability to provide deterministic transmission. To meet the stringent deterministic requirements of time-sensitive traffic, the mainstream traffic management mechanism time-aware shaper (TAS) relies on time synchronization among network devices. TAS schedules periodic traffic transmission using preallocated time windows. However, in real networks, time-sensitive traffic may not be precisely forwarded as scheduled, thus failing to achieve the expected performance. A fundamental reason is that the statically planned transmission schemes cannot accommodate dynamic time synchronization errors. To address this problem, we propose a novel TSN traffic scheduling strategy called robust TAS (RTAS), which utilizes a dual-queue gating structure to define a new scheduling rule for absorbing time synchronization errors to guarantee the real-time performance of scheduled traffic (ST). We conducted extensive simulations on OMNeT++ to study the performance of RTAS in industrial automation scenarios. The results show that RTAS enables deterministic transmission with imperfectly synchronized clocks and minimizes the impact of time synchronization errors on ST.

Time-Sensitive Networking (TSN), as an enhancement based on Ethernet, can ensure deterministic traffic transmission with low delays and minimal jitters. However, TSN switches have only eight priority queues inherited from Ethernet at each egress port, which limits the flexibility and efficiency of traffic scheduling, as well as the support for developing traffic management mechanisms. Although per-flow queues boost scheduling and Quality of Service (QoS), static per-flow hardware queues in switches are considered unpractical due to resource limits. In this article, we leverage the limitation of buffer size on the number of concurrent flows in shared buffer TSN switches to design Dynamic Per-Flow Queues (DFQ). DFQ only maintains a fixed number of virtual queues determined by the buffer size and dynamically manages the mapping between virtual queues and active flows to provide the capability of per-flow queuing. By constructing Flow Mapping Table (FMT) with content-addressable memory (or hash bucket), DFQ can quickly match, create, and recycle queues to multiplex limited switch resource. We prototype DFQ on an FPGA switch and evaluate its performance in different scenarios. Experimental results show that DFQ can decrease the overhead of per-flow isolation with minimal impact on delay and throughput, indicating that DFQ is an effective per-flow queues solution.

TSN is widely used in industrial automation networks because it can provide deterministic transmission services for critical data. Cyclic Queuing and Forwarding (CQF) is used to shape critical data. However, unexpected data errors may occur due to transient failures like electromagnetic interference. IEEE 802.1CB provides a solution to tolerate such failures by transmitting multiple replicas of data over disjoint paths. However, this solution introduces network resources wastage. Compared to redundant transmission, retransmission can reduce resource waste, but may violate the determinism in TSN. To address this issue, we propose a fault-tolerant mechanism for CQF that supports retransmission, called fault-tolerant CQF (FT-CQF). FT-CQF adopts the Go-Back-N concept to resist failure. Therefore, it does not violate the original transmission sequence of frames. On the basis of standard CQF, FT-CQF occupies an additional queue to cache replicas of Time-Trigger (TT) flows and reserves time slots to forward them. FT-CQF will forward or remove these replicas based on the ACK information. Non-TT flows can use this time slot to transmit when replicas are removed. We implemented FT-CQF on OMNeT++ and verified the performance of FT-CQF. Simulation experiments show that FT-CQF is effective in terms of reliability, bandwidth consumption, and delay.

Cyclic Queuing and Forwarding (CQF) configures the same cycle length on the flow path, resulting in certain flows unschedulable. Enhanced CQF (ECQF) based flow aggregation utilizes variable cycle length to address this issue. However, it remains a conceptual model without a concrete implementation. In this paper, we propose a jointly optimize aggregation cycle and flows' offsets (JACO) mechanism to achieve ECQF-based flow aggregation. We also design an incremental heuristic algorithm for JACO. Finally, we evaluate the performance of JACO in different scenarios using OMNet++ simulation platform. Compared with ECQF, the results show that JACO reduces latency and improves resource utilization.

Dynamic Per-Flow Queues (DFQ) extend queues from per-class to per-flow in Time-Sensitive Networking (TSN) switches that overcome large resource consumption by dynamically mapping a fixed number of physical queues to active flows. It can implement per-flow queuing with much less on-chip resource. Compared to brute-force hardware queues, DFQ prototyped on an FPGA, can effectively manage more per-flow queues, allowing for improved priority scheduling with minimal throughput and latency impact.

Time-sensitive networking (TSN) provides determin-istic time-sensitive transmission services for critical data at the link layer. Cyclic Queuing and Forwarding (CQF) defined by IEEE 802.1Qch is used for critical data transmission. However, unexpected data errors may occur due to transient faults like electromagnetic interference. At present, the solution to such faults defined in the IEEE TSN standards is to transmit multiple data copies on redundant paths, which introduces network resources wastage. Compared to redundant transmission, retransmission can reduce resource waste, but may violate the deterministic transmission guarantee in TSN. To tackle with this issue, we propose a time-redundant fault-tolerant mechanism for CQF, called fault-tolerant CQF (FT-CQF). On the basis of standard CQF, FT-CQF occupies an additional queue to cache copies of Time- Trigger (TT) flows and reserves time slots to forward them. According to the returned CRC-related messages, FT-CQF will decide whether to forward these copies. Non- Ttflows can also be transmitted during this time when copies are not required to be forwarded. We implement FT-CQF in OMNeT++, and verify the performance of FT-CQF in typical network scenarios. The extensive simulation experiments show that FT-CQF is effective in terms of fault-tolerant effects, consumed resources, delay, and jitter.

The rapid growth of the blockchain size is a major bottleneck hindering its implementations in data-heavy applications. Current efforts improve the distributed storage ways and transactions' storage mechanisms of blockchain, however, the blockchain distribution and integrity are destroyed. Simplified Payment Verification (SPV) is closely related to blockchain storage, but the current solutions did not explore the privacy-preserving SPV. In this paper, we propose a new storage structure for blockchain transactions, called Coloring Index (CI), to reduce the blockchain's space occupation. Specifically, we devise an index building algorithm to simply calculate the indices of transactions for the sake of information concealing. By improving the Coloring Embedder for multi-sets query, we can store the indices into the Coloring Embedder to achieve the structured storage of transactions with small space occupation. Using CI, SPV query proceeds without revealing the user's address, thereby achieving secure data sharing in applications such as the intelligent vehicles' communications and distributed IoT. We prove CI's security against malicious full nodes when establishing possible connections between the address and the user. The experiments show that blockchain systems using our CI store one time more transactions than Merkle tree and half more than Bloom filter.

The surging interest in cryptocurrency has revitalized the research for digital signature schemes with strong security. In particular, signature schemes are investigated to resist the malleability attacks in cryptocurrency platforms. However, existing signature schemes only conquer partial malleability attacks due to various sources of attacks. Other solutions of new transaction realizations cannot simultaneously avoid the malleability attacks on both standard and contract transactions. Furthermore, the malleability attack becomes more stubborn in fast clearing applications. In this paper, we propose SigNT, an accessional signature scheme with unmalleable transaction implementations. The key of SigNT is an improved interactive signature scheme for securely instant confirmation of transactions. Unlike standard signatures, this signature is generated by the owner and block producers. Combining it with several other optimizations (i.e., hash execution of intermediate transactions and secret-based claiming conditions), SigNT achieves complete resistance against malleability attacks in both the standard and contract transactions. As an example, we show an implementation in Bitcoin with the “providing a deposit” protocol. The security analysis and comparative experiments demonstrate that SigNT has the best resistance against malleability attacks than previous malleability solutions. Besides, better performance is achieved than other schemes.

Proof of Stake powered blockchains account for general trends in existing consensus mechanisms. However, existing PoS protocols are vulnerable to the nothing at stake and long range attacks, which allow attackers to gain unfair shares based on costless simulations and malicious sale information. In a decentralized setting, these securities are limited as each node is unregulated. To address these problems, we introduce a proof-of-hardware-stake (PohS) consensus mechanism and a regulatory mechanism based on a consortium blockchain. Our approach is implemented in a sharding blockchain to scale the consensus. Since any node on the network cannot fake information, the blockchain trustless won not be decreased by the reliance on a consortium blockchain. Under the competing rule of PohS consensus mechanism, adversaries can issue the long range attack with at most$10^{-3}$probability. The regulatory mechanism implements the regulation of costless simulations at the nothing stake attack. We prove that our design is secure (e.g.,51% and selfish mining) against adversarial stakes less than 51% by adopting the square root of stakes for competition. Our proof also highlights the security of double-spending and long range attacks. Simulations are conducted to compare the efficiency of our approach with Ethereum and Ouroboros.

Ciphertext retrieval under heterogeneous data sets is a critical concern in the cloud-assisted Internet of Things (IoT). Previous ciphertext retrieval schemes eliminate computation burden and security concerns to some extent, but cannot support the encrypted heterogeneous data sets. To solve this problem, in this article we propose a transparent ciphertext retrieval system regardless of programming language, accessible platforms, and heterogeneity of data sets. The retrieval system is a novel combination of the proposed access and integration middleware with a current encrypted cloud database system. The middleware enables cross-language and cross-platform queries over various database systems, besides, it schedules the designed data integration method in heterogeneous databases to realize cross-database queries over the encrypted cloud data sets. The proposed ciphertext retrieval system achieves efficient data sharing among different IoT applications with various database systems. We prove that the system guarantees data security by avoiding malicious hackers. Extensive experiments show that our design is efficient and feasible in practice.

Blockchain allows for secure management of a shared ledger by agreement protocols, where transactions are validated over network without central authorities. Although the agreement protocol has been thoroughly conducted of propagation and consensus researches, mobility of nodes in unstructured overlay networks has not received much attention. Besides, current dynamic propagation schemes waste travel hops and are low of delivery ratio. In this article, we propose a social characteristic-based propagation-efficient protocol NefSBFT to agree on system state plus consensus mechanisms in public blockchains. We devise a propagation technique (travel hops of at least$\frac{1}{3}$savings, delivery ratio above 0.93, etc.) for message multicasting when exploiting real nodes’ social characteristics of intermittent connectivity and frequent partitions. This propagation technique is executed in the improved FastBFT to achieve transaction ordering and block verification, thus, no controllable mobility is required during the whole system’s execution. NefSBFT achieves fast propagation, small message complexity and few resource consumption of travel hops and running nodes for complete protocol execution. We analyze NefSBFT’s security against DDOS attack of non-primary failure. The experiments show the performance tradeoff under different parameters, compare the propagation efficiency with Erlay and Flooding, and clarify NefSBFT’s impact on the whole system performance through comparison.

Many cloud encryption methods have been proposed to achieve the encryption and decryption of users' data stored on public cloud database, and there are also some studies on heterogeneous database connection access methods, but none of them can implement the users's transparent (cross-language and cross-platform) or heterogeneous access to encrypted database on public cloud. To solve these problems, we modularly comply a middleware system in a private cloud by using the Mysql protocol and heterogeneous database data integration technology, which is applied in a hybrid cloud environment to achieve the users' transparent access to heterogeneous encrypted database. We talk about the preliminary assessment on the system security. Besides, the experimental evaluation testifies the system performance through separately testing time costs for the users to execute transparent access to individual and heterogeneous encrypted database.