This Letter proposes a reliable and lightweight key generator based on a novel bit-self-test arbiter physically unclonable function (BST-APUF). The BST-APUF adds a delay detection circuit into a classical APUF to automatically test the delay deviation that produces each bit of the PUF response and generates a reliability-flag for each response to indicate its reliability. The key generator collects robust responses and produces a secure key using a cryptographic entropy accumulator. FPGA implementation results show that the overhead and the helper data length of the authors proposed key generator are significantly lower than that of the state-of-the-art schemes when generating a 128-bit key with a bit error rate of 10 −9. Notations C i , R i , F i challenge, response, reliability-flag T c delay threshold generated by threshold generator ΔT delay difference between the upper and lower paths ⊙ exclusive-NOR (XNOR) operation MUX, DMUX multiplexer, demultiplexer REG, LFSR, NVM register, linear feedback shift register, non-volatile memory Introduction: Physically unclonable functions (PUFs) promise to be critical hardware primitives that can be used to provide unique identities or produce and store cryptographic keys against tamper attacks for IoT devices [1]. However, PUF outputs are unreliable across environmental variations (voltage and temperature); and thus, cannot be used directly as keys. The error correction code (ECC) mechanisms are required to extract the stable keys from the noise data. However, most of ECC implementations are too expensive for resource-constrained IoT devices with potential safety hazards [2]. In this Letter, we propose an efficient and reliable Arbiter PUF (APUF) using bit self-test strategy and present a reliable and lightweight key generator based on the proposed PUF without using any ECC mechanisms.

Physically unclonable functions (PUFs) promise to be a critical hardware primitive for billions of Internet of Things (IoT) devices. The arbiter PUF (A-PUF) is one of the most well-known PUF circuits. However, its FPGA implementation has a poor reliability, and error correction codes (ECCs) are usually needed to eliminate the noise in the responses, which incur additional high hardware overhead and require NVM for helper data storage. In this paper, we present a highly reliable arbiter PUF with improved uniqueness using the bit-self-test (BST) strategy. A delay detection circuit is added into a classical arbiter PUF to test the delay deviation that produces each bit of the PUF response in real-time and mark the response as reliable using a reliability flag when the delay deviation is significantly more than a predefined threshold. Then, the robust responses can be used. We implemented the BST-arbiter PUF on a Xilinx Artix 7 FPGA. The test results show that the selected responses achieve outstanding performance where the bit error rate is less than 10-9 , the bias is 50.3%, and the uniqueness is 49.1%. Thus, the BST-APUF, which drastically reduced the ECC overhead, can be applied to lightweight cryptography applications.

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In order to solve the problem of applying super-tonnage prestressing force to the gate pier in the process of dam reinforcement, this paper presents a comparative study on the three groups of test specimens of prestressed counterbore self-locking anchor rod and unbonded prestressed anchor cable. T show: (a)both methods satisfy the needs of applying prestress, the experiment conducted on the gate pier that is to be renovated has tested the prestress loss of two schemes and the concrete stress in both free section and anchor section after applying the prestress. The results and counterbore self-locking anchor rod boasts shorter anchorage section and better applicability. (b) the anchorage sections of two schemes generate additional tensile stress, and the maximum additional tensile stress in the anchor rod features 54% less than that of anchor cable, smaller range of additional tensile stress and more reasonable stress state of concrete than that of anchor cable.

Background: This study aimed to systematically evaluate the efficacy of laparoscopic radical cystectomy (LRC) surgical therapy in patients with bladder cancer (BC), and to provide evidence for the clinical treatment of BC. Methods:The Embase, Ovid, PubMed, Medline, Springer, and Web of Sciences database were searched to screen articles with clinical controlled trials on LRC treatment of BC. The Cochrane Handbook 5.0.2 software and Review Manager 5.3 software were adopted to evaluate the risk of bias and to perform a meta-analysis of the included articles in this study.Results: A total of 12 articles were obtained, including 1,283 research cases. The meta-analysis results showed that relative to the control group (Ctrl), the observation group (Observ group) had significantly lower intraoperative blood loss (IBL) after LRC [mean difference (MD) =−458.75; 95% confidential interval