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In the research area of card-based cryptography, designing committed-format AND protocols that are efficient in terms of the number of required cards is a major topic. Such an AND protocol should receive two pairs of face-down (physical) cards representing two secret input bits, from which it should securely produce a pair of face-down cards representing the AND value of the two bits via a series of actions, such as shuffling and turning over cards, along with some helping cards. The number of required cards typically depends on allowed kinds of shuffling operations. This paper focuses on “RC-protocols” meaning to be able to use only the random cut (RC), which is the easiest shuffling operation to implement. The best committed-format AND RC-protocol currently known was devised by Stiglic in 2001, where eight cards are used (i.e., his protocol needs four helping cards). Since then, it has been an open question to determine whether there exists a committed-format AND RC-protocol using less than eight cards. In this study, we answer to the question: We propose a six-card committed-format AND RC-protocol (using exactly two random cuts). Therefore, we can reduce the number of required cards by two.

In 1989, den Boer presented the first card-based protocol, called the “five-card trick,” that securely computes the AND function using a deck of physical cards via a series of actions such as shuffling and turning over cards. This protocol enables a couple to confirm their mutual love without revealing their individual feelings. During such a secure computation protocol, it is important to keep any information about the inputs secret. Almost all existing card-based protocols are secure under the assumption that all players participating in a protocol are semi-honest or covert, i.e., they do not deviate from the protocol if there is a chance that they will be caught when cheating. In this paper, we consider a more malicious attack in which a player as an active adversary can reveal cards illegally without any hesitation. Against such an actively revealing card attack, we define the t-secureness, meaning that no information about the inputs leaks even if at most t cards are revealed illegally. We then actually design t-secure AND protocols. Thus, our contribution is the construction of the first formal framework to handle actively revealing card attacks as well as their countermeasures.

In card-based cryptography, designing AND protocols in committed format is a major research topic. The state-of-the-art AND protocol proposed by Koch, Walzer, and Härtel in ASIACRYPT 2015 uses only four cards, which is the minimum permissible number. The minimality of their protocol relies on somewhat complicated shuffles having non-uniform probabilities of possible outcomes. Restricting the allowed shuffles to uniform closed ones entails that, to the best of our knowledge, six cards are sufficient: the six-card AND protocol proposed by Mizuki and Sone in 2009 utilizes the random bisection cut, which is a uniform and cyclic (and hence, closed) shuffle. Thus, a question has arisen: “Can we improve upon this six-card protocol using only uniform closed shuffles?” In other words, the existence or otherwise of a five-card AND protocol in committed format using only uniform closed shuffles has been one of the most important open questions in this field. In this paper, we answer the question affirmatively by designing five-card committed-format AND protocols using only uniform cyclic shuffles. The shuffles that our protocols use are the random cut and random bisection cut, both of which are uniform cyclic shuffles and can be easily implemented by humans.

Card-based cryptography is an attractive and unconventional computation model; it provides secure computing methods using a deck of physical cards. It is noteworthy that a card-based protocol can be easily executed by non-experts such as high school students without the use of any electric device. One of the main goals in this discipline is to develop efficient protocols. The efficiency has been evaluated by the number of required cards, the number of colors, and the average number of protocol trials. Although these evaluation metrics are simple and reasonable, it is difficult to estimate the total number of operations or execution time of protocols based only on these three metrics. Therefore, in this paper, we consider adding other metrics to estimate the execution time of protocols more precisely. Furthermore, we actually evaluate some of the important existing protocols using our new criteria.

A threat of eavesdropping display screen image of information device is caused by unintended EM leakage emanation. QR bar-code is capable of error correction, and its information is possibly read from a damaged screen image from EM leakage. A new design of QR bar-code proposed in this paper uses selected colors in consideration of correlation between the EM wave leakage and display color. Proposed design of QR bar-code keeps error correction of displayed image, and makes it difficult to read information on the eavesdropped image.

In card-based cryptography, a commitment to a Boolean value is usually represented by two face-down cards of different colors or numbers, whose order specifies the one-bit value (namely, 0 or 1). One of the most important primitives in card-based cryptography is a "copy protocol," which is supposed to make two identical copies of a given commitment. In the literature, there are several copy protocols, which can be categorized by kinds of shuffles they use; this paper focuses on those using only the so-called random cut, which is the simplest shuffle, and we propose two copy protocols that are more efficient than the existing ones. Specifically, we first work on a standard deck of cards and design a six-card copy protocol using three random cuts (on average). Since the previous protocol needs 5.5 random cuts, our protocol improves upon it. Next, we shift our attention to the case of a two-colored deck of cards, and construct a six-card copy protocol using three random cuts (on average). Because the previous protocol requires eight cards, our protocol uses two cards fewer than the previous one (although it uses one more shuffle). In addition, going back to the standard-deck setting, we provide a four-card XOR protocol using only one random cut for the first time.

International audience; We propose a technique to construct physical Zero-Knowledge Proof (ZKP) protocols for puzzles that require a single loop draw feature. Our approach is based on the observation that a loop has only one hole and this property remains stable by some simple transformations. Using this trick, we can transform a simple big loop, which is visible to anyone, into the solution loop by using transformations that do not disclose any information about the solution. We illustrate our technique by applying it to construct physical ZKP protocols for two Nikoli puzzles: Slitherlink and Masyu.

Card-based cryptography typically uses a physical deck comprising black and red cards to perform secure computations, where a one-bit value is encoded using a pair of cards with different colors such that the order of black to red represents 0 and red to black represents 1. One of the most fundamental classes of card-based protocols is the class of “card-minimal” n-input AND protocols, which require 2n face-down cards as input to securely evaluate the AND value after applying a number of shuffles; here, the 2n cards are minimally required to describe an n-bit input. The best n-input AND protocols currently known use two shuffles for \(n=2\), five shuffles for \(n=3\), and \(n+1\) shuffles for \(n>3\). These upper bounds on the numbers of shuffles have not been improved for several years. In this work, we present a better upper bound for the \(n=3\) case by designing a new card-minimal three-input AND protocol using only two shuffles. Therefore, our proposed protocol reduces the number of required shuffles from five to two; we believe that this is a significant improvement.

Card-based protocols are used to perform cryptographic tasks such as secure multiparty computation using a deck of physical cards. While most of the existing protocols use a two-colored deck consisting of red cards and black cards, Niemi and Renvall in 1999 constructed protocols for securely computing two-input Boolean functions (such as secure logical AND and XOR computations) using a commonly available standard deck of playing cards. Since this initial investigation, two-input protocols with fewer cards and/or shuffles have been designed, and by combining them, one can perform a secure computation of any Boolean circuit. In this paper, we directly construct a simple card-based protocol for the three-input AND computation. Our three-input AND protocol requires fewer cards and shuffles compared to that required when applying any existing two-input AND protocol twice to perform the three-input AND computation. Our protocol is unique in the sense that it is card minimal if we use two cards to encode a single bit.

Zero-Knowledge Proof (ZKP) is a cryptographic technique that enables a prover to convince a verifier that a given statement is true without revealing any information other than its truth. It is known that ZKP can be realized by physical objects such as a deck of cards; recently, many such “card-based” ZKP protocols for pencil puzzles (such as Sudoku and Numberlink) have been devised. In this paper, we shift our attention to graph theory problems from pencil puzzles: We propose card-based ZKP protocols for the graph 3-coloring problem and the graph isomorphism problem. Similar to most of the existing card-based ZKP protocols, our two protocols have no soundness error. The proposed protocols can be implemented without any technical knowledge, and the principle of zero-knowledge proof is easy to understand. In particular, our protocol for the graph isomorphism problem requires only three shuffles regardless of the sizes of a pair of given graphs. In addition, to deal with our proposed protocols more rigorously, we present a formal framework for card-based ZKP protocols which are non-interactive and have no soundness error.

Before starting to play a two-player board game such as Chess and Shogi (namely, Japanese chess), we have to determine who makes the first move. Players’ strategies of Chess and Shogi often rely on whether they will move first or not, and most players have their own preferences. Therefore, it would be nice if we can take their individual requests into account when determining who goes first. To this end, if the two players simply tell their preferable moves to each other, they will notice the other’s strategy. Thus, we want the players to determine the first move according to their requests while hiding any information about them. Note that this problem cannot be solved by a typical way done in Chess, namely, a coin-flipping. In this paper, we formalize this problem in a cryptographic perspective and propose a secure protocol that solves this problem using a deck of physical cards. Moreover, we extend this problem to the multi-player setting: Assume that there is a single prize in a lottery drawing among more than two players, each of who has an individual secret feeling ‘Yes’ or ‘No’ that indicates whether he/she really wants to get the prize or not. If one or more players have ‘Yes,’ we want to randomly and covertly choose a winner among those having ‘Yes.’ If all of them have ‘No,’ we want to randomly pick a winner among all the players. We solve this extended problem, which we call the “covert lottery” problem, by proposing a simple card-based protocol.

Executing a card-based cryptographic protocol is an attractive way to perform secure multiparty computation (MPC) with a deck of physical cards. Crepeau and Kilian at CRYPTO 1993 proposed card-based AND and XOR protocols that can deal with a logical conjunction and exclusive-or of variables. Their protocols use a familiar shuffling action called a random cut that can be easily implemented by humans, while the numbers of required cards and shuffles are not small enough to be efficient and the protocols are Las Vegas algorithms, i.e., they are not finite-runtime. Several researchers have improved upon the protocols for a quarter of a century. Eventually, there are many AND protocols in the literature, some of which are quite efficient and practical to execute. By contrast, there are only three XOR protocols including the Crepeau--Kilian protocol mentioned above. In this paper, we design an efficient XOR protocol using only random cuts; the numbers of required cards and shuffles are six and two (which is fixed), respectively. Our proposed XOR protocol is the first construction of a finite-runtime XOR protocol if we restrict ourselves to use only random cuts.

Side-channel attack is a serious threat that can retrieve the secret key by analyzing side channel information leakage from cryptographic devices. The analysis to extract the key is affected by quantization error in the measurement. We conducted measurements on correlation power analysis (CPA) by controlling the quantization resolution and the authors showed that the key extraction is difficult in the reduced resolution, and there is a limit to the extraction efficiency.

A risk of eavesdropping the screen image of a device by exploiting unintended electromagnetic (EM) emanation is reported. Estimating the source of EM emanation from the device is an efficient method to protect the device from eavesdropping by use of EM shield to reduce unintended EM emanation. The authors estimated, multiple EM emanation sources by observing the EM distribution at leakage frequencies of a tablet and a display monitor. The mersurement, showed estimation of the EM emanation sources such as a cable that connects LCD panel to the integrated circuit in the tablet, HDMI cable, and the edge of the screen.

Card-based protocols allow to perform secure multiparty computations using a deck of physical cards, and rely on shuffle actions such as the (normal) shuffle, the random cut, and the random bisection cut. A shuffle action is mathematically defined by a pair of a permutation set (which is a subset of the symmetric group) and a probability distribution on it; while one can theoretically consider any shuffle action in mind, he or she may be unable to determine whether it can be easily implemented by human hands. As one of the most general results, Koch and Walzer showed that any uniform closed shuffle (meaning that its permutation set is a subgroup and its distribution is uniform) can be implemented by human hands with the help of additional cards. However, there are several existing protocols which use non-uniform and/or non-closed shuffles. To implement these specific shuffles, Nishimura et al. proposed an idea of using (special) physical cases that can store piles of cards as well as Koch and Walzer proposed an implementation of a specific non-closed shuffle with additional cards. Because their implementations handle a limited class of non-uniform and/or non-closed shuffles, it is still open to find a general method for implementing any shuffle. In this paper, we solve the above problem; we implement “any” shuffle with only additional cards, provided that every probability of its distribution is a rational number. Therefore, our implementation works for any non-closed or non-uniform shuffle (if the distribution is rational as above).

Secure multiparty computation (MPC) is a cryptographic technique that enables us to evaluate a predetermined function over players’ private inputs while hiding information about the inputs. MPC can be conducted using a “private PEZ protocol,” that uses PEZ candies and a dispenser. Specifically, in a private PEZ protocol, players first fill a predetermined sequence of candies in a dispenser. Then, each player in turn privately pops out a number of candies, wherein the number depends on their private input (without anybody else knowing how many candies pop out). The next candy to be popped out of the dispenser indicates the output value of the function. Thus, private PEZ protocols are fun and useful. One drawback would be that every player must pop out candies from the dispenser secretly, implying that a private PEZ protocol is vulnerable to dishonest players, for example, a player could peep the candies inside the dispenser. To overcome this drawback, we herein propose MPC protocols that do not need private actions such as secretly popping out candies after the setup (although each player rearranges the candies secretly in a setup phase, any illegal actions can be caught). That is, we construct a computational model of “public-PEZ cryptography,” where any protocol within the model can be publicly executed. Especially, the proposed public-PEZ AND protocol, which uses only five candies and two dispensers, is simple and easy for conducting a secure computation of the AND function.

In this paper, we present a new information leakage threat combining intentional electromagnetic interference (IEMI) and observations of EM leakage. In previous studies, the analysis of secret key information in cryptographic modules using fault injection has led to methods whereby faults can be injected via low-voltage IEMI. However, the timing of fault injections cannot be controlled with this approach, and it is difficult to obtain faulty ciphertexts for use in secret key analysis by differential fault analysis (DFA). To overcome this problem, we propose a method for estimating the fault-injection timing by detecting characteristic fluctuations in the EM leakage from the device. As a result, it may be possible to implement a realistic secret information analysis method applicable to a wide range of devices. First, to show the feasibility of the proposed method, we describe an experiment using an on-chip fault-injection circuit that can control the injection timing. Furthermore, we apply a fault analysis method that combines the injection timing estimation method and fault injection by IEMI in a practical experimental environment. We select useful faulty ciphertexts using the proposed method, and then perform secret key analysis by DFA. Experimental results demonstrate that the secret key can be successfully analyzed.

Card-based cryptographic protocols can perform secure computation of Boolean functions. In 2013, Cheung et al. presented a protocol that securely produces a hidden AND value using five cards; however, it fails with a probability of 1/2. The protocol uses an unconventional shuffle operation called an unequal division shuffle; after a sequence of five cards is divided into a two-card portion and a three-card portion, these two portions are randomly switched so that nobody knows which is which. In this paper, we first show that the protocol proposed by Cheung et al. securely produces not only a hidden AND value but also a hidden OR value (with a probability of 1/2). We then modify their protocol such that, even when it fails, we can still evaluate the AND value in the clear. Furthermore, we present two five-card copy protocols (which can duplicate a hidden value) using unequal division shuffle. Because the most efficient copy protocol currently known requires six cards, our new protocols improve upon the existing results. We also design a general copy protocol that produces multiple copies using an unequal division shuffle. Furthermore, we show feasible implementations of unequal division shuffles by the use of card cases.

In 1989, den Boer presented the first card-based protocol, called the “five-card trick” that securely computes the AND function using a deck of physical cards via a series of actions such as shuffling and turning over cards. This protocol enables a couple to confirm their mutual love without revealing their individual feelings. During such a secure computation protocol, it is important to keep any information about the inputs secret. Almost all existing card-based protocols are secure under the assumption that all players participating in a protocol are semi-honest or covert, i.e., they do not deviate from the protocol if there is a chance that they will be caught when cheating. In this paper, we consider a more malicious attack in which a player as an active adversary can reveal cards illegally without any hesitation. Against such an actively revealing card attack, we define the t-secureness, meaning that no information about the inputs leaks even if at most t cards are revealed illegally. Subsequently, we design a 1-secure AND protocol. Thus, our contribution is the construction of the first formal framework to handle actively revealing card attacks and their countermeasures.

It is established that secure computation can be achieved by using a deck of physical cards. Almost all existing card-based protocols are based on a specific deck of cards. In this study, we design card-based protocols that are executable using any deck of cards (e.g., playing cards, UNO, and trading cards). Specifically, we construct a card-based protocol for any Boolean function based on any deck of cards. As corollaries of our result, a standard deck of playing cards (having 52 cards) enables secure computation of any 22-variable Boolean function, and UNO (having 112 cards) enables secure computation of any 53-variable Boolean function.

In card-based cryptography, designing AND protocols in committed format is a major topic of research. The state-of-the-art AND protocol proposed by Koch, Walzer, and Hartel in ASIACRYPT 2015 uses only four cards, which is the minimum permissible number. Their protocol»s minimality relies on somewhat complicated shuffles having non-uniform probabilities of possible outcomes. Restricting the allowed shuffles to "practical»» ones, namely uniform closed shuffles, to our knowledge, six cards are sufficient: The six-card AND protocol proposed by Mizuki and Sone in 2009 utilizes the random bisection cut, which is a uniform and cyclic (and hence, closed) shuffle. Thus, a question has arisen: Can we improve upon this six-card protocol using only practical shuffles? In other words, whether there exists a five-card AND protocol in committed format using only uniform closed shuffles has been one of the most important open questions in this field. In this paper, we answer the question affirmatively by designing a five-card committed-format AND protocol using only practical shuffles. The shuffles that our protocol uses are random cut and random bisection cut, both of which are uniform cyclic shuffles and can be easily implemented by humans.

A method of the fault injection to a cryptographic equipment injects intentional electromagnetic interference (IEMI) on its power line. An IEMI fault is caused when the injection is superimposed on the rising portion of the clock signal, and the vulnerability increases if the clock pulse has long rise time. If the rise time is short, the clock signal has widely spread frequency spectrum, and may cause electromagnetic disturbance. The clock rise time should be considered as trade-off between resistance against fault injection and electromagnetic compatibility (EMC). An experimental study showed how clock rise time effects on occurrence of fault injection, and distribution of high frequency components of the clock signal was observed.

A method for evaluating electromagnetic (EM) information leakage through EM emanation from displays is introduced. This method judges the leakage by detecting an audio signal without needing to reconstruct the image. A leakage frequency of 140 MHz for the display was successfully obtained using a controlled image.

Card-based cryptography is an attractive and unconventional computation model; it provides secure computing methods using a deck of physical cards. It is noteworthy that a card-based protocol can be easily executed by non-experts such as high school students without the use of any electric device. One of the main goals in this discipline is to develop efficient protocols. The efficiency has been evaluated by the number of required cards, the number of colors, and the average number of protocol trials. Although these evaluation metrics are simple and reasonable, it is difficult to estimate the total number of operations or execution time of protocols based only on these three metrics. Therefore, in this paper, we consider adding other metrics to estimate the execution time of protocols more precisely. Furthermore, we actually evaluate some of the important existing protocols using our new criteria.

In the history of cryptography, many cryptographic protocols rely on random coin tosses to discuss their provable security. Although flipping coins is indispensable in this manner, the coins themselves have never been in the spotlight. Therefore, we would like to make physical coins go up to the stage of cryptography, as a deck of physical playing cards has been used to perform a secure multi-party computation. Such a card-based protocol is helpful both to perform a secure computation without any black-box computers and to understand the principles of secure protocols. In this paper, we propose a new framework of secure multi-party computation using physical coins, named a coin-based protocol. Whereas a face-down card can conceal the information about its face side, one side of a coin leaks the information of its other side. Hence, more careful design is required for a secure coin-based protocol than the card-based one. We introduce a computational model of the coin-based protocol and explicitly give protocols for NOT, AND, and copy computations. We also discuss how to implement the protocols in practice.

Card-based protocols provide secure multi-party computation using a deck of physical cards, via a series of operations such as shuffling and turning over cards, which are supposed to be executed by humans. Although almost all existing protocols have been designed to be perfectly secure, operative errors by humans would cause information leakage. In this paper, we propose a technique for analyzing information leakage due to operative errors in card-based protocols. To be specific, we introduce a concept, which we call a “probability trace,” and propose a new diagram for displaying how much information leaks, by enhancing the KWH diagram proposed by Koch, Walzer, and Hartel. By applying our diagram to a card-based protocol with an operative error, we can precisely reveal the leakage of players’ inputs from the protocol output. We also discuss an application of the diagram to human-error-free implementations of the existing six-card AND protocol.

This paper investigates the mechanism underlying faulty outputs from cryptographic modules due to intentional electromagnetic interference IEMI, which causes information leakage in electronic devices without disrupting their functions or damaging their components. We show this fault mechanism through experiments using the faulty ciphertexts and pulse injection to a specific round in the encryption process. The experimental results indicate that faulty outputs from cryptographic modules are caused by setup time violation in the cryptographic module.

An efficient analysis method in the frequency domain for the extraction of information under the degradation of signal-to-noise ratio SNR is proposed. When the electromagnetic emission from the cryptographic module on the hardware is analyzed, the electromagnetic fields caused by operation on the other modules interfere to the electromagnetic field from the cryptographic module. Therefore, the amount of the measured data required for the extraction of information under the condition of degraded SNR increases and the analysis for this increase in data needs additional computation time. In order to accelerate the analysis under the degradation of SNR, we focus on only the processing of analysis target data. Furthermore, the signal of information and noises is separated with the analysis on the frequency domain. The proposed method is examined through experiments.

In 2015, Koch et al. proposed a five-card finite-runtime committed protocol to compute securely the AND function, showing that their protocol was optimal: there is no protocol computing the AND function with four cards in finite-runtime fashion and committed format. Thus, necessary and sufficient numbers of cards for computing single-bit output functions are known. However, as for two-bit output functions, such an exact characterization is unknown. This paper gives a six-card (or less) protocol for each of all two-bit output functions and proves that our finite-runtime committed protocols are optimal by providing a lower bound. In other words, we give the necessary and sufficient number of cards for any two-bit output function to be computed by a finite-runtime committed protocol. Our lower bound can also be applied to any function which outputs more than two bits.

Consider a face-down card lying on the table such that we do not know whether its suit color is black or red. Then, how do we make identical copies of the card while keeping its color secret? A partial solution has been devised: using a number of additional black and red cards, Niemi and Renvall proposed an excellent protocol which can copy a face-down card while allowing only a small probability of revealing its color. In contrast, this paper shows the nonexistence of a perfect solution, namely, the impossibility of copying a face-down card with perfect secrecy. To prove such an impossibility result, we construct a rigorous mathematical model of card-based cryptographic protocols; giving this general computational model is the main result of this paper.

This paper presents an efficient map generation technique for evaluating the intensity of electromagnetic (EM) radiation associated with information leakage for cryptographic devices at the printed circuit board level. First, we investigate the relation between the intensity of the overall EM radiation and the intensity of EM information leakage on a cryptographic device. For this purpose, we prepare a map of the magnetic field on the device by using an EM scanning system, after which we perform correlation electromagnetic analysis (CEMA) at all measurement points on the device, including points above the cryptographic module. The examined device is a standard evaluation board for cryptographic modules (side-channel attack standard evaluation board), where a cryptographic circuit is implemented on one of the field-programmable gate arrays on the board. With this experiment, we demonstrate that both an EM radiation map and an information leakage map can be generated simultaneously by scanning the board only once. We also confirm that the generated map is in good agreement with the corresponding map obtained from exhaustive CEMAs.

This paper presents a novel analysis of electromagnetic (EM) information leakage from cryptographic devices, based on the electromagnetic interference (EMI) theory. In recent years, side-channel attack using side-channel information (e.g., power consumption and EM radiation) is of major concern for designers of cryptographic devices. However, few studies have been conducted to investigate how EM information leakage changes according to device's physical parameters. In this paper, we introduce a cryptographic device model to analyze EM information leakage based on the EMI theory in a systematic manner. This device model makes it possible to acquire the frequency characteristics of EM radiation depending on physical parameters, such as board size and power-line length, accurately. The analysis results show that EM information leakage can be explained by the major EMI parameters such as board size and cable length attached to the board. In addition, we demonstrate that the intensity of EM information leakage from a generic device is also explained by board size and cable length.

This paper presents a new type of intentional electromagnetic interference (IEMI) which causes information leakage in electric devices without disrupting their functions or damaging their components. Such IEMI could pose a severe threat to a large number of electric devices with cryptographic modules since it can be used for performing fault injection attacks, which in turn allows for obtaining faulty outputs (i.e., ciphertexts) from cryptographic modules and exploiting them to reveal information about secret keys. Such faulty outputs are usually generated by inducing faults into target modules through modification or invasion of the modules themselves. In contrast, IEMI-based fault injection can be performed on the target modules from a distance by using an off-the-shelf injection probe, without leaving any hard evidence of the attack. We demonstrate the impact of the aforementioned IEMI through experiments using the Advanced Encryption Standard, which is one of the ISO/IEC 18033 block ciphers, implemented as a module on a standard evaluation board. The experimental results indicate that generating exploitable faults is feasible and, therefore, such IEMI presents a tangible threat to various existing electric devices and systems that use cryptographic modules for secure communication and transactions.

Authentication based on cryptographic protocols is a key technology for recent security systems. This paper proposes a new authentication method that utilizes the side channel that already exists in many authentication systems. Side-channel analysis has been studied intensively from the attacker viewpoint and is best known for key-recovery attacks against cryptographic implementations using physical information. In this paper, reversing the traditional thought, we propose to use the key-dependent side-channel information constructively to enhance, or as an alternate to, existing cryptographic protocols. Using Advanced Encryption Standard (AES)-based authentication as an example, we demonstrate, based on experiments using an Field Programmable Gate Array (FPGA), that the side-channel information leaked from cryptographic devices is sufficiently unique for authentication.

It is known that secure multiparty computation can be performed using physical cards with identical backs, and numerous card-based cryptographic protocols have been proposed. Almost all existing protocols require multiple cards that have the same pattern on their face sides; thus, a standard deck of playing cards cannot be used for executing these protocols. However, there is one exception: Niemi and Renvall’s protocols, proposed in 1999, can be used with standard playing cards. In this paper, we continue their efforts to improve secure multiparty computation using a standard deck of playing cards, and propose efficient AND, XOR, and copy protocols that require significantly fewer shuffles compared to previous protocols.

By using a deck of cards, it is possible to realize a secure computation. In particular, since a new shuffling operation, called a random bisection cut, was devised in 2009, many efficient protocols have been designed. The shuffle functions in the following manner. A sequence of cards is bisected, and the two halves are swapped randomly. This results in two possible cases, depending on whether the two halves of the card sequence are swapped or not. Because there are only two possibilities when a random bisection cut is performed, it has been suggested that information regarding the result of the shuffle could sometimes be leaked visually. Thus, in this paper we propose some methods for implementing a random bisection cut without leaking such information.

Cryptographic modules are now mounted on many commercial products for secure transactions and communications. On the other hand, a new class of physical attacks against cryptographic modules, which is called “side channel attack,” is drawing much attention due to the non-invasive nature and effectiveness. This paper presents an overview of the research trends in side-channel attack and the related activities to counteract such attacks and evaluate the security of cryptographic modules.

Electromagnetic (EM) radiation from information hardware under normal operating conditions can compromise secret information (EM, information leakage), such as operations or processed data contained in the hardware. Methods for analyzing EM radiation with the intention of extracting secret information have been proposed, and EM side-channel attacks on cryptographic hardware are a major concern. This paper investigates how EM information leakage changes with the configuration of the information hardware, focusing on the frequency characteristics of the hardware. We assume that the frequency characteristics of the EM radiation correspond to physical aspects of the hardware configuration. To address the issue of information leakage, this paper presents a novel analysis of EM radiation from information hardware by using a model circuit board. Using this model, we show that the intensity of the EM emissions can be correlated to the layout of the hardware. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 182(4): 1–9, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22386

When contact failure occurs in a connector in a coaxial high-frequency (HF) signal transmission line, it is well known that common-mode (CM) radiation occurs on the line. We focus on contact conditions in a connector causing such CM radiation. Experiments and simulations verify that CM radiation increases as the contact resistance increases. While the CM current strongly depends on the distribution pattern of contact resistances at a low resistance, the CM current does not depend on these pattern at a high resistance. Our results indicate that it is important to maintain a symmetrical distribution of contact spots whenever the number of such spots is four or more.