Abstract Passwords remain the most widely used authentication method and play a critical role in maintaining practical security. Previous research has highlighted the influence of linguistic factors on the strength of user-created passwords, demonstrating that evaluating passwords created by users speaking languages other than English requires specific contextual knowledge. Despite this, no prior studies have specifically investigated the passwords of Japanese users. This paper presents the first study of the characteristics of Japanese user-created passwords across websites offering five types of services. Using a dataset of 48.5 million real-world leaked passwords, we conduct a comprehensive analysis of various aspects of password behavior. Our findings reveal several unique characteristics of Japanese web passwords. For instance, Japanese passwords exhibit greater dispersion compared to those of English and Chinese users, with keyboard-walk patterns being particularly prevalent among the most frequently used passwords. To address these findings, we propose a suggestion for helping users improve their password selection strategies. The experimental results demonstrate that the suggestion led to 82.15% and 93.88% of passwords being strengthened as evaluated by two effective PSMs, and reduced the cracking success rate of PCFG-guesser by up to 56.12%.

Abstract Visual cryptography (VC) is a powerful technique with high security and requires no PC or device to reconstruct the secret information. Progressive visual cryptography (PVC) is a variation of the VC scheme in which the quality of the reconstructed image is improved by increasing the number of shared images. The previous study focused directly on maximizing the value of the quality in the completely reconstructed image; thus, there is a difference in the quality of the shared images. In this paper, we focus on the aforementioned issue and propose a new approach based on inductive reasoning. Our basic idea is to maximize the quality of the reconstructed images each time the number of shared images increases. We call this method the bottom-up approach. Moreover, hitherto, PVC has been evaluated based on the value of relative difference or by sight. Such evaluation methods are only subjective or difficult to execute without the knowledge of basis matrices. In addition, PVC users cannot easily confirm the effectiveness of their shared images. In this paper, we propose a new information-theoretic evaluation method for PVC, which only uses shared images, to solve the aforementioned problems. Our proposed method can objectively and quantitatively evaluate PVC based on the numerical value, and PVC users can easily confirm the effectiveness of their shared images.

RECTANGLE is a 64-bit block cipher with 80 and 128-bit key length proposed by Zhang et al(Lightweight Cryptography Workshop 2015). Integral attack is one of the typical evaluation tools of block cipher. The designers showed 7-round integral distinguisher. On the other hand, we find 8-round integral distinguisher which has balanced columns by our proposal search method of integral distinguisher. In this paper, we present the first integral attack on reduced-round RECTANGLE. Based on 8-round distinguisher, we can attack 12-round RECTANGLE-128 with computational complexity 2^109.98 with partial sum technique. Also, we can attack 10-round RECTANGLE-80 with computational complexity 270.08.

Integral distinguisher is the main factor of integral attack. In the conventional search strategy of integral distinguisher (ID), there are two steps. In the first step, first order ID is obtained. In the second step, first order ID is extended by increasing the order. We find it is problematic to apply the conventional strategy for Feistel ciphers whose number of sub blocks N is large such as TWINE and LBlock (N = 16). To solve the problem, we propose new search strategy which has large search scope and feasibility in realistic computational condition. By the reduction of the computational complexity, it is reduced from O((nN)×(2mn)) to O(N×2mn). And for the acceleration of the experiment, we use GPGPU (general-purpose computing on graphics processing units) platform. By using GPGPU platform, we can test substantially higher order ID than existing CPU platform. We execute computer experiment to discover the precise fifteenth order ID of TWINE and LBlock by proposal strategy. As a result, we find new fifteenth order ID which has 8 balanced sub blocks (32-bit) after 15-round encryption both in TWINE and LBlock. These results are the most precise evaluatiPon of TWINE and LBlock.

Intrusion Detection System (IDS) detects attacks using pattern files which are known as “signature”. Effectiveness of detection depends on the kind of signature. In this paper, we propose a signature generation method using Discrete Fourier Transformed regards payload between client and server as discrete waveform. Regarding normal communication spectrum as noise, we can clarify the characteristics of attack sessions. From the viewpoint of spectrum analysis, our method detect unknown attack session. The proposed method simulated using Kyoto2006+ dataset which is currently used as intrusion detection evaluation. As the result, we have 5% of false positives for detecting attacks.

We numerically evaluate the wavelength division multiplexing (WDM) data transmission of coherent phase-shift keying (PSK) and quadrature amplitude modulation (QAM) signals in optical fiber communication and deep-space communication channels with conventional homodyne-based(dyne-type) detections and various quantum detection strategies. We show the quantitative gap between these detection strategies and especially in the quantum-limited region where the quantum noise seriously limits the transmission rate. For an extremely weak signal input power, there is a crucial gap between the capacity limit and the transmission rates of the WDM system with dyne-type detections. We show that this gap is filled by applying a collective square root detection (SRD) only for each channel, not necessary for quantum collective decoding among WDM channels.