To deal with the increasing number of cyber-attacks, intrusion detection system (IDS) plays an important role in monitoring and ensuring the security of the computer network. With the power of machine learning and deep learning, intelligent IDS systems have gained increasing attention due to their efficiency and high classification accuracy. However, the premise of machine learning/deep learning is that the data must be in one central entity (e.g., server) to train the model. This causes additional concerns, such as data transmission costs and privacy leakage. Federated learning complements this shortcoming with a privacy-preserving decentralized learning technique. In federated learning, the data are not shared with the server, local model training is performed where the data reside and only the model parameters are exchanged with the server. This work investigates the federated learning-based IDS approach in the context of IoT data to study the main challenges imposed by federated learning. Two main issues, such as data heterogeneity and poisoning attacks launched by malicious clients, are the main focus of this study. As real-world IoT datasets are heterogeneous, we propose a personalized federated learning-based IDS approach to handle imbalanced data distributions. Moreover, a curious yet malicious client can poison the local data or model to corrupt the global intrusion detection model due to the distributed nature of federated learning, where the central server has no control over the client’s local training process. This study demonstrates that the existence of a malicious client can degrade the performance of the federated learning-based IDS model. Accordingly, we propose a robust approach called pFL-IDS to combat poisoning attacks against the federated learning-enabled IDS on heterogeneous IoT data. Our approach introduces mini-batch logit adjustment loss to local model training to obtain a personalized model tailored to each local data distribution. Moreover, we design a detection mechanism at the server to identify malicious agents by considering the cosine similarity of local models from the non-poisoned client’s centroid. The non-poisoned centroid is determined from the similarity between the pre-computed global model and the local models. If the poisoning attack is successful, poisoned clients will be closer to the pre-computed global model; any models further from the pre-computed model are taken as the non-poisoned clients. With this two-phase client similarity alignment, we identify poisoned clients and restrict their aggregation on the global intrusion detection model. In comparison with the baseline methods, we demonstrate that our pFL-IDS can detect poisoning attacks without compromising performance.

User-centric data sharing is essential to encourage citizens' active participation in the digital economy. One key to smart cities, a form of the digital economy, is the promotion of public use of citizen data. Nevertheless, it is not easy to utilize data without citizens’ consent. In this study, we took a technological approach to these issues. User-managed access (UMA) is a well-known framework for delegating resource access rights to others on the Internet. In UMA, authorization mechanisms are designed to be centralized so that resource owners can centrally manage access rights for various resources stored in different domains. However, the lack of transparency in the authorization mechanism is a barrier to its implementation in large-scale systems such as smart cities. In this study, we developed a blockchain-based cross-domain authorization architecture that enables a resource-sharing ecosystem in which organizations that wish to utilize data can freely trade with each other. The proposed architecture solves the transparency problem that conventional authorization systems have had by designing the authorization mechanism on blockchain technology. We implemented the proposed architecture as smart contracts and evaluated its processing performance. The resultant time required for delegating access rights and accessing resources was less than 500 ​ms. Furthermore, we found that the fluctuation in the processing time overhead was small. Based on these results, we concluded that performance degradation with the proposed architecture is minor.

This paper studies adaptive modulation techniques aiming to implement secure transmission in practical communication systems imposed with finite alphabet constraints. As a baseline, the logarithm barrier method is applied to solve the adaptive modulation problem formulated with an inequality constrained secrecy capacity maximization. However, the interested problem requires to jointly solve plural sub-problems to select the best alphabet-set, which incurs a high complexity issue for the baseline technique due to identifying infeasible cases. Hence, we propose a new cache-aided power optimization algorithm that finds the optimal solution with a statistically independent complexity order of the number of the sub-problems. Simulation results obtained in MIMO-ME scenarios verify the effectiveness of the new cache-aided bisection (C-bisect) method that it achieves normalized throughput performance of 0.95.

In this paper, we investigate the error correction capability of irregular LDPC codes. We have shown relationships between the decoding failure and the structures of the Tanner graph of irregular LDPC codes under the Gallager A algorithm. In this analysis, we focused on the structures of connecting degree-two variable nodes, called 2-cycle. In this paper, we present new structures of the subgraph which induces the decoding failure of irregular LDPC codes under the Gallager A algorithm. Furthermore, we analyze relationships between the newly found structures of subgraph and the decoding failure of irregular LDPC codes.

Many physical devices and sensors make it possible to obtain more localized data and applications which provide more localized information for users will appear. Generally, those applications use a storage server for computing location-dependent data. Traffic of Internet of Things (IoT) devices may cause concentration, when data is stored into a server. It is desirable that each location-dependent data is stored in each area, because each data request can be processed there and each user can get the data from a nearby server. This paper proposes the virtual storage with Key-Value Stores over Named Data Networking. In proposed system, the location-dependent data is cached in local servers, which are located at network edge, and each user can get the data from a nearby local server. We evaluate the proposed system by simulation from the views of delay time and energy consumption. We compare the proposed system with the conventional system, in which all data is stored in a certain server and all users retrieve it from the server. We show that the proposed system can reduce the both of delay time and energy consumption compared with the conventional system.

By exchanging the information on the status and the surrounding environment between devices, devices can determine the optimal action. We focus on the construction of a digital signature scheme for local broadcast, which allows the devices with limited resources to securely transmit broadcast messages. A multi-group authentication scheme that enables a node to authenticate its membership in multi verifiers by the sum of the secret keys has been proposed for its use on devices with limited resources. This paper proposes a multi-group signature scheme by converting the multi-group authentication via the Fiat-Shamir transform. In the proposed scheme, a sender can sign a message by the secret keys which multiple certification authorities issue and the signature can validate the authenticity and integrity of the message to multiple verifiers. By comparing the proposed scheme with a code-based signature scheme, where a sender signs a message by individual secret key as many times as the number of the secret key and each of verifiers verify each signature, the proposed scheme provides efficient multi-group signature in terms of the amount of transmitted data.

While many two-party fair exchange protocols have been proposed, more than three-party fair exchange protocol is required depending on a type of applications. Asokan et al. have proposed a multi-party fair exchange protocol for mesh topology. This scheme can be adapted to all kinds of topologies but requires much communication costs, which is 4n(n-1) passes in the all n-participators honest cases and 8n2-n-10 passes in the worst case. In previous works, more efficient and multi-functional schemes specialized for a kind of topologies have been proposed but most of these are for ring topology and star topology. Zhou et al. have proposed an efficient multi-party contract signing protocol for line topology. It is shown the two protocols such that a simple protocol which is completed with 4(n-1) passes in the all honest cases and 5n-3 passes in the worst case and an optimized protocol which is completed with 3(n-1) passes in the all honest cases and 4n-2 passes in the worst. This result means that a fair exchange protocol for line topology is efficient in a number of communications nevertheless a certified email protocol specialized for line topology has not been proposed. That is, a certified email protocol run on line topology is only a protocol for mesh proposed by Asokan et al. adapted to line topology, therefore there is large room for reducing a number of communications by specializing for a certified email protocol. In this paper, we propose a three-party certified email protocol for line topology towards a design of n-party protocol. The proposed protocol has such basic properties of certified email as fairness, non-repudiation, trusted third party invisibility and timeliness, as same as the previous works. Our scheme is completed with eight passes in the case of all honest and twelve passes in the worst. The communication cost is less than the Asokan et al.'s scheme with 24 (n=3) passes even if the all n-participators are honest.

Cassuto and Blaum proposed new error correcting codes which are called symbol-pair codes. They gave a coding framework for channels whose outputs are overlapping pairs of symbols in storage applications. It is called symbol-pair read channel. The pair distance and pair error are used in symbol-pair read channel. Cassuto et al. and showed Yaakobi et al. presented decoding algorithms for symbol-pair codes. However, their decoding algorithms cannot always correct errors whose number is not more than half the minimum pair distance. In this paper, we propose a new decoding algorithm using the syndrome of symbol-pair codes. In addition, we show that the proposed algorithm can correct all pair errors within the pair error correcting capability.

In the analysis of maximum-likelihood decoding performance of low-density parity-check (LDPC) codes, the weight distribution is an important factor. Some methods based on the error impluse method have presented in order to estimate the weight distribution of LDPC codes. However, these methods have no scheme which determine the number of codeword in LDPC codes. In this paper, we propose a reliability-based computation method for the weight distribution of LDPC codes using the probabilistic algorithm. Using the proposed method, we can determine the weight distribution of LDPC codes with small failure probability.

No polynomial classical algorithms can distinguish between the 3-round Feistel cipher with internal permutations and a random permutation. It means that the 3-round Feistel cipher with internal permutations is secure against any chosen plaintext attack on the classical computer. This paper shows that there exists a polynomial quantum algorithm for distinguishing them. Hence, the 3-round Feistel cipher with internal permutations may be insecure against a chosen plaintext attack on a quantum computer. This distinguishing problem is an instance that can be efficiently solved by exploiting the quantum parallelism. The proposed algorithm is the first application of Simon's algorithm to cryptographic analysis.

The performance of LDPC codes decoded by iterative algorithm depends on the structural properties of their underlying Tanner graphs. For discrete memoryless channels, error patterns dominating the frame error rate (FER) in the error floor region are termed trapping set. We have shown approximate examinations of small trapping sets of LDPC codes using the probabilistic algorithm. In this paper, we propose an efficient method for the detailed evaluation of the FER of LDPC codes in the error floor region. The accuracy of the FER lies on the failure probability of the number of trapping sets determined by our probabilistic algorithm and the FER estimated by the importance sampling.

On the binary erasure channel (BEC), the performance of low-density parity-check (LDPC) codes decoded by iterative algorithms is estimated by the small stopping sets in the codes. The size of smallest stopping set is called the stopping distance. Since it depends on the structure of parity-check matrix for the code, we can construct the parity-check matrix by adding dependent rows so that the stopping distance is equal to the minimum distance. The stopping redundancy is defined as the smallest number of rows in such a parity-check matrix. In this paper, we propose a probabilistic algorithm for computing the stopping redundancy of LDPC codes. Additionally, we show numerical results of computing the stopping redundancy of (155,64), (504,252) and (1008,504) LDPC codes.

One of the serious problems in a fingerprinting system is the collusion attack such that several users combine their copies of a same content to modify/delete the embedded fingerprints. In IWSEC2007, we have proposed a collusion-resilient fingerprinting scheme based on the CDMA technique. In this paper, we formalize the model of collusion from the viewpoint of a communication channel, and design an effective detector considering the hierarchically embedded signals as a fingerprint.

On the binary erasure channel, the performance of LDPC codes decoded by iterative algorithms is estimated by small-size stopping sets. We have proposed a probabilistic algorithm for computing the minimum size of stopping sets of LDPC codes. In this paper, we analyze the probability and the complexity of finding the minimum-size stopping sets, and give an error probability of determining the minimum size of stopping sets after processing our algorithm. Additionally, we show the numerical results of computing the minimum size of stopping sets of several LDPC codes. In these result, we could compute the minimum size of stopping sets with high reliability.

On the binary erasure channel, the performance of LDPC codes decoded by iterative algorithms is dominated by small-size stopping sets, especially minimal stopping sets. In this paper, we propose a probabilistic algorithm for computing the minimum size of stopping sets of LDPC codes. In this algorithm, we generate efficiently small-size stopping sets by using the relation between small-size stopping sets and low-weight codewords. In numerical experiments, we could compute the minimum size of stopping sets of LDPC codes of length about 500, 1000 and 5000 with high reliability, and could find smaller stopping sets than that found by conventional methods.

Digital fingerprinting is used to trace back illegal users, where unique ID known as digital fingerprints is embedded into a content before distribution. On the generation of such fingerprints, one of the important properties is collusion-resistance. Binary codes for fingerprinting with a code length of theoretically minimum order were proposed by Tardos, and the related works mainly focused on the reduction of the code length were presented. In this paper, we present a concrete and systematic construction of the Tardos’s fingerprinting code using a chaotic map. Using a statistical model for correlation scores, a proper threshold for detecting colluders is calculated. Furthermore, for the reduction of computational costs required for the detection, a hierarchical structure is introduced on the codewords. The collusion-resistance of the generated fingerprinting codes is evaluated by a computer simulation.

Low-density parity-check (LDPC) codes achieve outstanding performance by the sum-product decoder. Its performance approaches the maximum-likelihood (ML) decoding performance at high SNR region. Upper bounds on the error probability of the ML decoded LDPC codes can be computed using the weight distribution. Recently, X.-Y. Hu et al. presented an approximate algorithm for estimating the weight distribution of LDPC codes. However, the weight distribution computed by their method depends on the iterative decoding algorithm, and is not always estimated exactly. In this paper, we propose a probabilistic method for computing the low-part weight distribution of LDPC codes. Using our method, the approximate weight distribution of LDPC codes can be computed with high accuracy

A key advantage of SSL (secure socket layer) VPN is that no specialized client software is required. When a user requests access to a server, the SSL client module, which is a Java applet code, is downloaded into the host first. However, it is quite likely that not all applications run well, because a client cannot connect with a server through an HTTPS tunnel in some applications. Moreover, there is the possibility that we can not use the VPN connections when the SSL port is under denial of service (DoS) or distributed DoS (DDoS) attack. We propose a port randomized VPN architecture such that any application can use the VPN and the VPN has strength against DoS or DDoS attack. The proposed VPN uses the same Java applet as existing SSL VPNs use, but the function of the applet, which we call mobile code, is dynamically changed by Java remote method invocation (RMI). The VPN client applet can cooperate with a VPN server and a firewall in the server side.

This paper proposes a new feedback picture sequence control (FPSC) for providing better QOS and more effective usage of network resource in ATM networks. The FPSC utilizes the feedback mechanism of the ABR service and the flexibility of MPEG video coding in order to resolve the collision of I-pictures at switches. The FPSC requires only a very little modification of usage of RM cell in the ABR service. We also describe the MPEG encoder which can change the number of pictures in a GOP. Simulation results show that the FPSC can improve the QOS such as the cell loss ratio and mean buffering delay in the cell buffer of the switch.

Recently D.K. Pradhan, S.K. Gupta and M.G. Karpovsky (1990) affirmed that the codes generated by (x- alpha )(x- beta ) were not Reed-Solomon, where alpha and beta were roots of the distinct primitive polynomials of degree m. It was assumed that beta = alpha /sup 8/, where s-1 and 2/sup m/-1 were mutually prime. The authors show that under the above assumption the respective codes are Reed-Solomon codes.>

A key equation of the remainder decoding algorithm is presented. It is noted that the key equation presents a general relationship between the errors on the received codeword and the coefficients of the remainder polynomial. It is shown that several key equations proposed by L. Welch and E.R. Berlekamp (1983) and others can be derived from the proposed key equation. Useful properties of the key equations in fast decoding of Reed-Solomon codes are given.>

Discrete-time Wiener-Hopf equations (DTWHEs) over finite fields are considered. It is shown that solving the DTWHE is equivalent to performing division over finite fields. The proof provides a new interpretation of the relationship between bit-serial multiplication and DTWHEs. The interpretation enables bit-serial multiplication over GF(2/sup m/) to be understood more easily. As an example, bit-serial multiplication methods for multiplying any two elements that can be done without performing any transformation, or with only a simple transformation of the bases, are presented.>