In this work, we introduce a new mechanism for constructing multi-client searchable encryption (SE). By tactfully leveraging the RSA-function, we propose the first multi-client SE protocol that successfully avoids per-query interaction between data owner and client. Therefore, our approach significantly reduces the communication cost by eliminating the need for data owner to authorize client queries at all times. To be compatible with the RSA-based approach, we also present a deterministic and memory-efficient ‘keyword to prime’ hash function, which may be of independent interest. Further, to improve efficiency, we put forward a more generic construction from set-constrained PRFs. The construction not only inherits the merits of our first protocol, but also achieves an enhanced security (against untrusted clients), where colluding attack among clients is also taken into account. Both protocols are instantiated via the recent representative SE protocol by Cash et al. with support of boolean queries. At last, we implement our proposed protocols and comprehensively evaluate their performance to demonstrate their practicability and scalability.

In the process of NIST postquantum cryptography standardization, module lattice-based Dilithium has been chosen as one of the three third-round finalists for digital signature schemes. More evaluations of its implementation efficiency on different platforms are required for further competition. In this article, we present an efficient implementation of Dilithium on a field-programmable gate array (FPGA) system-on-chip (SoC) platform. To achieve a high computation speed, we design a hardware architecture to perform the main body of the algorithm, and the preprocessing and postprocessing steps are accomplished by the processor. For the hardware architecture, we take some optimizations on the most time-consuming operations, that is, polynomial multiplication, hashing, and sampling. Polynomial multiplications are accelerated by the radix-4 number theoretic transform (NTT) architecture with a conflict-free memory mapping scheme. A fast modular multiplication on the Dilithium modulus is proposed to support the underlying calculations. For hashing and sampling, we design a multipurpose hashing unit and a compact sampling unit. The cooperative work of the two units accelerates the sampling process significantly. We implement the Key Generation, Signing, and Verification algorithms of the round-3 Dilithium at all three security levels on the Xilinx Zynq-7000 platform. Compared with existing software/hardware codesign for Dilithium on a similar platform, our design achieves about $17\times $ and $40\times $ improvements in performance for the Signing and Verification algorithms, respectively, at the cost of about $7.8\times $ more look up table (LUT) resources.

Side-channel attacks are an increasingly important concern for the security of cryptographic embedded devices, such as the SIM cards used in mobile phones. Previous works have exhibited such attacks against implementations of the 2G GSM algorithms (COMP-128, A5). In this paper, we show that they remain an important issue for USIM cards implementing the AES-based MILENAGE algorithm used in 3G/4G communications. In particular, we analyze instances of cards from a variety of operators and manufacturers, and describe successful Differential Power Analysis attacks that recover encryption keys and other secrets (needed to clone the USIM cards) within a few minutes. Further, we discuss the impact of the operator-defined secret parameters in MILENAGE on the difficulty to perform Differential Power Analysis, and show that they do not improve implementation security. Our results back up the observation that physical security issues raise long-term challenges that should be solved early in the development of cryptographic implementations, with adequate countermeasures.

In recent years, deep learning techniques have received significant attention in the side-channel community due to their state-of-the-art performance in profiled attacks against embedded devices. Compared with template attacks, deep learning-based attacks can deal with the high dimensionality of trace and misalignment without pre-processing. However, the performance of attacks is very sensitive to the network architecture, especially when considering masking countermeasures. Although previous works have shown the potential of neural networks to break the first-order masking, the inner-working of how the network combines the leakage of mask and masked value is still unclear and could be suboptimal. To reduce this gap, we propose to embed product combination, which has been proved to be the best combination function in noisy situations, into the design of neural networks. To this end, we introduce a bilinear convolutional neural network (in short, B-CNN) for efficient profiled attacks against the widely used masking countermeasure. In order to interpret the inner-working and decision-making of B-CNN, we propose a new visualization tool called layer-wise correlation that can reveal the points of interest and help to understand the combination of leakages. We evaluate our networks on several public datasets, e.g., ASCAD and CHES CTF 2018. The results indicate that B-CNN converges significantly faster than classic CNN models, even using a very limited number of profiling traces (e.g., 8000 profiling traces for the ASCAD dataset). Moreover, our networks perform even systematically better (w.r.t. the number of attack traces) than the current state-of-the-art results on all the investigated datasets.

Cloud computing provides users with convenient data storage services, which simultaneously poses various security concerns, the integrity of outsourced data has been termed as one of the most concerning security issues. Certificateless public auditing not only enables a third-party auditor (TPA) to check data integrity, but also avoids complex certificates management and inherent drawbacks of key escrow. Up to date, a few certificateless public auditing schemes have been proposed, without providing fast data dynamics or protecting the identity privacy of users. In this paper, we propose a lightweight conditional anonymous certificateless public auditing (CACPA) scheme, supporting much faster data dynamics in cloud storage systems. Based on a homomorphic hash function, we design a certificateless signature and integrate it into the construction of CACPA, reducing the computational costs of TPA substantially. CACPA achieves conditional identity privacy preservation, anyone cannot infer the real identity of a user based on outsourced data, only the private key generator (PKG) can revoke the users when some misbehaviors occur. We provide security analysis of CACPA, and conduct performance evaluation demonstrating the lightweight advantages of CACPA, and therefore it is suitable for auditors with resource-constrained mobile devices.