Practical reusable garbled circuits with parallel updates

Secure two-party computation provides a way for two parties to compute a function, that depends on the two parties’ inputs, while keeping them private. Known since the 1980s, Yao’s garbled circuits appear to be a general solution to this problem, in the semi-honest model. Decades of optimizations have made this tool a very practical solution. However, it is well known that a malicious adversary could modify a garbled circuit before submitting it. Many protocols, mostly based on cut-&-choose, have been proposed to secure Yao’s garbled circuits in the presence of malicious adversaries. Nevertheless, how much an adversary can modify a circuit and make it still executable has not been studied yet. The main contribution of this paper is to prove that any modification made by an adversary is equivalent to adding/removing NOT gates arbitrarily in the original circuit, otherwise the adversary can get caught. Thereafter, we study some evaluation functions for which, even without using cut-&-choose, no adversary can gain more information about the inputs by modifying the circuit. We also give an improvement over most recent cut-&-choose solutions by requiring that different circuits of the same function are used instead of just one.

Homomorphic encryption (HE) schemes enable computing functions on encrypted data, by means of a public Eval procedure that can be applied to ciphertexts. But the evaluated ciphertexts so generated may differ from freshly encrypted ones. This brings up the question of whether one can keep computing on evaluated ciphertexts. An i-hop homomorphic encryption scheme is one where Eval can be called on its own output up to i times, while still being able to decrypt the result. A multi-hop homomorphic encryption is a scheme which is i-hop for all i. In this work we study i-hop and multi-hop schemes in conjunction with the properties of function-privacy (i.e., Eval's output hides the function) and compactness (i.e., the output of Eval is short). We provide formal definitions and describe several constructions. First, we observe that bootstrapping techniques can be used to convert any (1-hop) homomorphic encryption scheme into an i-hop scheme for any i, and the result inherits the function-privacy and/or compactness of the underlying scheme. However, if the underlying scheme is not compact (such as schemes derived from Yao circuits) then the complexity of the resulting i-hop scheme can be as high as nO(i). We then describe a specific DDH-based multi-hop homomorphic encryption scheme that does not suffer from this exponential blowup. Although not compact, this scheme has complexity linear in the size of the composed function, independently of the number of hops. The main technical ingredient in this solution is a re-randomizable variant of the Yao circuits. Namely, given a garbled circuit, anyone can re-garble it in such a way that even the party that generated the original garbled circuit cannot recognize it. This construction may be of independent interest.

Pairing-based cryptography (PBC), a variant of elliptic curve cryptography (ECC), uses bilinear maps between elliptic curves and finite fields to enable several novel applications beyond traditional key exchange and signatures [1]. Fig. 1 shows two such applications - (a) signature aggregation, where arbitrarily large number of signatures are aggregated into one to resolve communication bottleneck in mesh networks such as blockchain [9], and (b) functional encryption, which allows computation on encrypted data with a function embedded in the decryption key [7]. In particular, pairing-based function-hiding inner product functional encryption [10] can be used for privacy-preserving data classification, thus enabling a new paradigm in the field of secure computation.

This paper reports an advanced passive piezoelectric shunt damping technique called broadband piezoelectric shunting. The shunt circuit for the broadband shunting is built with a reactance neutralizing circuit, which is designed with operational amplifier circuits to maximize the parallel reactance of the shunt circuit over a wide frequency band. It is different from the earlier shunt circuits, either used for the single- or multiple-mode shunting, which were built with inductors or simulated inductor circuits. In these earlier shunt circuits the anti-resonant frequency of the shunt circuit, with the inclusion of the piezoelectric transducer, was tuned with the inductor to a specific frequency to match with the natural frequency of the mode to be controlled. We first describe how the concept of the broadband shunt circuit was conceived and developed. We next report the shunt damping experiments performed on three difference structures: a thin aluminum cantilever beam, a two-wing aluminum cantilever beam, and a small-scale thermoplastic composite fairing. We have successfully demonstrated broadband amplitude reduction of structural vibration modes over a wide frequency band using the broadband shunt-damping technique. More detailed experimental results will be presented.

Secure Two-Party Computation (STC) allows two mutually untrusting parties to securely evaluate a function on their private inputs. While tremendous progress has been made towards reducing processing overheads, STC still incurs significant communication overhead that is in fact prohibitive when no high-speed network connection is available, e.g., when applications are run over a cellular network. In this paper, we consider the fundamental problem of securely computing a minimum and its argument, which is a basic building block in a wide range of applications that have been proposed as STCs, e.g., Nearest Neighbor Search, Auctions, and Biometric Matchings. We first comprehensively analyze and compare the communication overhead of implementations of the three major STC concepts, i.e., Yao’s Garbled Circuits, the Goldreich-Micali-Wigderson protocol, and Homomorphic Encryption. We then propose an algorithm for securely computing minima in the semi-honest model that, compared to current state-of-the-art, reduces communication overheads by 18 % to 98 %. Lower communication overheads result in faster runtimes in constrained networks and lower direct costs for users.

Access control schemes in predicate encryption can effectively reduce the risk of information leakage in the inner product function encryption (IPFE). However, when we try to transition from identity-based IPFE to attribute-based IPFE, the fine-grained nature of attributes induces some unprecedented access control problems. These problems not only lead to incorrect inner product computation results from attribute-based IPFE but also inevitable passive information leakage induced by large attribute set secret key. At the same time, since the above problems are not common in identity-based IPFE and traditional ABEs, they cannot be properly addressed by existing schemes. To address the above problems, we introduce a new scheme - Ciphertext Policy Based Inner Product Function Encryption (CP-IPFE). In this scheme, we propose to use a "label vector" to label the attributes of n-dimensional vectors and encode them onto the relevant information, so as to ensure that the attribute-based IPFE will not output incorrect inner-product computation results; establishing a leaf node set-based "reverse access control policy" to realize reverse access control on "risky ciphertext", ensures that "risky ciphertext" will not be leaked encrypted-information by the secret key of large attribute sets. In addition, CP-IPFE also has the characteristics of traditional attribute encryption and supports more fine-grained access control. Finally, we prove the CPA security of the CP-IPFE in the GGM model and show a detailed application of the CP-IPFE on a general-purpose platform.

Multi-Client Attribute-Based Unbounded Inner Product Functional Encryption, and More

Function-Hiding Zero Predicate Inner Product Functional Encryption from Pairings

Post-Quantum Secure Inner Product Functional Encryption Using Multivariate Public Key Cryptography

Ultrasonic motors can be driven by burst voltage to obtain micro-stepping motion, and the corresponding step size depends on the load and cycle number of the applied ac driving voltage in one burst. The rotor of the motor achieves a step motion through a process of startup-acceleration-deceleration-stop. To obtain a large torque (or thrust force) and quick startup, a large vibration amplitude of a stator and a high growth rate are desired; thus, a large mechanical quality factor and a high electromechanical coupling factor are required. However, the stator vibration decays for a long time before it stops because of low mechanical energy loss; meanwhile, the rotor moves a big step. Hence, there is contradiction between thrust force and resolution/response time. This paper presents a new drive method to improve the step resolution and response time while keeping the torque by damping control. By simply adding a switch and a shunting damp circuit and connecting the shunting circuit to ultrasonic motors at the end of a drive burst signal, the stator vibration attenuates more rapidly and the step size is reduced. First, the damping effect of the piezoelectric system with a passive resonant shunting circuit (a resistor and an inductor connected in series) on the free stator of a bar-type rotary traveling wave ultrasonic motor has been tested. Next, a drive circuit comprising electronic switches and the shunting circuit is designed and utilized for measuring the performance of the motor. Experimental results have well proven the proposed method.

To construct a smart sound absorber in the low-frequency range with a wide control band, a piezoelectric ceramic (PZT) shunted with multiple resonance circuit is attached onto a micro-perforated panel (MPP) to perform as a smart sound absorber. The absorption can be controlled by the shunt circuit parameters conveniently. This smart micro-perforated panel (MPP) is investigated experimentally to explore the feasibility and design procedure in practical use. Based on the coupling among the acoustical, electrical, and mechanical fields, the proposed broadband sound absorber can achieve good acoustic performance on subwavelength scales. The electrical response of the shunt circuit is tested with a Network Analyzer. The acoustic performance of the smart sound absorber is measured in an impedance tube with the two-microphone transfer function method. The experimental results validate that the shunt circuit can resonate with the PZT patch at multiple frequencies, and hence improve the sound absorption of the smart absorber at these frequencies.

Piezoelectric passive control is a piezoelectric shunt damping technology that utilizes the piezoelectric effect of a piezoelectric material to convert the mechanical energy generated by the structural vibration of a sound wave incident on a piezoelectric device into electrical energy. By connecting a shunt circuit in parallel with the piezoelectric device, the resistance in the shunt circuit converts the electric energy into heat energy so as to achieve the purpose of suppressing the structural vibration and improving the sound absorption performance. In the article, the negative capacitance is used to counteract the capacitive reactance of the piezoelectric film, increase the electromechanical coupling coefficient of the piezoelectric film and improve the controllability of the system. We also analyze when a rigid piezoelectric material connected to the back of piezoelectric damping material, the method can improve the efficiency of electrical-acoustic conversion, and enhance the sound absorption ability of the material. At the same time, this paper also studies the role of rubber damping material in the piezoelectric shunt damping sound absorption layer, designed a sound absorbing structure with wide frequency range and high absorption coefficient.

The current sharing of the chips in parallel is one of the key points of the layout design of IGBT module. The current imbalance of the chips leads to imbalance losses and temperature, and increases the failure of the chip with highest temperature, so attention should be paid during the IGBT module design. In this paper, the asymmetric stray parameters of the circuit in parallel and the coupling between the gate circuit and the power circuit are analyzed by the equivalent circuit method, but the simulation results and the experimental results show that the stray inductances and resistances, extracted at the fixed frequency, can't reflect the electrical behaviors of the power and gate circuit. A method to extract the stray parameters is proposed in this paper, which can be used to reflect the current imbalance of the switching and conducting behaviors.

A mechanical-magnetic-electro bidirectional coupled dynamic model of a composite cantilever with magnetostrictive shunt damper is established, and the system's transfer functions and a key impedance impact factor are derived. For shunt vibration damping, H2 optimization criterion and the Nelder-Mead search method are used to obtain the optimal parameters of three circuits: resistance shunt (RS), capacitance shunt (CS), and resistance-CS (RCS). Comparisons between the calculated and measured results show that the proposed model can accurately describe the transmissibility vibration frequency responses of the system under RS and CS, and can predict the changing laws of the resonant frequency and the resonant peak with the shunt impedance. It is found that the RCS with negative shunt resistance can provide the peak attenuation rate 90.78%, which is higher than 70.44% of CS and 53.29% of RS, and has wider frequency broadband and faster vibration damping performances than CS and RS.

Electromagnetic shunt damping is a damping technique using an electromagnetic transducer. The damping technique is a simple method since a shunt circuit is only attached to the electromagnetic transducer. The disadvantage of this technique is sensitive to modeling error. Especially, in the case of using a resonant shunt circuit, the impedance model of the electromagnetic transducer in the high-frequency range is very important. However, we observed that the conventional model cannot represent the experimental results of frequency response in the high-frequency range. This paper proposes a novel impedance model that has higher accuracy compared with the conventional model. The proposed model considers eddy currents generated in electromagnetic transducer which has non-uniform physical parameters. Lumped parameter model is derived by spatial discretization. The order of the proposed model can be chosen arbitrarily. The validity of the proposed model is verified by experiments. The experimental result shows that the proposed model has higher accuracy compared with the conventional model.