48 research outputs found

    A new idea in response to fast correlation attacks on small-state stream ciphers

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    In the conference “Fast Software Encryption 2015”, a new line of research was proposed by introducing the first small-state stream cipher (SSC). The goal was to design lightweight stream ciphers for hardware application by going beyond the rule that the internal state size must be at least twice the intended security level. Time-memory-data trade-off (TMDTO) attacks and fast correlation attacks (FCA) were successfully applied to all proposed SSCs which can be implemented by less than 1000 gate equivalents in hardware. It is possible to increase the security of stream ciphers against FCA by exploiting more complicated functions for the nonlinear feedback shift register and the output function, but we use lightweight functions to design the lightest SSC in the world while providing more security against FCA. Our proposed cipher provides 80-bit security against TMDTO distinguishing attacks, while Lizard and Plantlet provide only 60-bit and 58-bit security against distinguishing attacks, respectively. Our main contribution is to propose a lightweight round key function with a very long period that increases the security of SSCs against FCA

    On designing secure small-state stream ciphers against time-memory-data tradeoff attacks

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    A new generation of stream ciphers, small-state stream ciphers (SSCs), was born in 2015 with the introduction of the Sprout cipher. The new generation is based on using key bits not only in the initialization but also continuously in the keystream generation phase. The new idea allowed designing stream ciphers with significantly smaller area size and low power consumption. A distinguishing time-memory-data tradeoff (TMDTO) attack was successfully applied against all SSCs in 2017 by Hamann et al. [1]. They suggested using not only key bits but also initial value (IV) bits continuously in the keystream generation phase to strengthen SSCs against TMDTO attacks. Then, Hamann and Krause [2] proposed a construction based on using only IV bits continuously in packet mode. They suggested an instantiation of an SSC and claimed that it is resistant to TMDTO attacks. We point out that storing IV bits imposes an overhead on cryptosystems that is not acceptable in many applications. More importantly, we show that the proposed SSC remains vulnerable to TMDTO attacks. To resolve security threat, the current paper proposes constructions, based on storing key or IV bits, that are the first to provide full security against TMDTO attacks. It is possible to obtain parameters for secure SSCs based on these suggested constructions. Our constructions are a fruitful research direction in stream ciphers

    FET model parameter extraction based on optimization with multiplane data-fitting and bidirectional search - a new concept

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    IEEE Transactions on Microwave Theory and Techniques4271114-1121IETM

    Dual 3-phase buck converter for multi-core CPUs power supply in mobile devices

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    A Joint Low-Power Cell Search and Frequency Tracking Scheme in NB-IoT Systems for Green Internet of Things

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    As a dedicated communication protocol for Internet-of-Things, narrowband internet of things (NB-IoT) needs to establish the communication link rapidly and reduce retransmissions as much as possible to achieve low power consumption and stable performance. To achieve these targets, the low-power scheme of the initial cell search and frequency tracking is investigated in this paper. The cell search process can be subdivided into narrowband primary synchronization signal (NPSS) detection and narrowband secondary synchronization signal (NSSS) detection. We present an NPSS detection method whose timing metric is composed of symbol-wise autocorrelation and a dedicated normalization factor. After the detection of NPSS, the symbol timing and fractional frequency offset estimation is implemented in a resource-efficient way. NSSS detection is conducted in the frequency domain with a calculation-reduced algorithm based on the features of NSSS sequences. To compensate the accumulated frequency offset during uplink transmission, a pilot-aided rapid frequency tracking algorithm is proposed. The simulation results of the proposed cell search scheme are outstanding in both normal coverage and extended coverage NB-IoT scenarios, and the accumulated frequency offset can be estimated with high efficiency

    Contact Resistance Parallel Model for Edge-Contacted 2D Material Back-Gate FET

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    Because 2D materials have adjust band gap, high mobility ratio, bipolar, anisotropy and flexibility characters, they have become the new direction for FET’s channel materials. According to the characteristics of the layers of 2D materials, the current transport characteristics can be improved by using the edge-contacted electrode. Moreover, the research on the current transfer mechanism between channel layers is the basis of the practical application of 2D transistors. In the research, the 2D material-MoS2 is used as the channel material, the back-gate transistors with different layers are prepared by dry etching and edge-contacted electrode structure. We also discuss the current transport mechanism of channel and established the channel resistance parallel transport model. The parallel model and TLM are used to analyze the contact resistance of the edge-contacted structure, and the total resistance, total contact resistance, and single-layer contact resistance of different layers are calculated. The parallel model is verified by dc test data. The number of channel layers is closely related to contact resistance, total resistance, and mobility. In addition, the of single MoS2 is about 7.27 kΩ·um. This contact resistance parallel model can also be applied to other 2D materials edge-contacted FET
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