Keiichi Iwamura

Secret Sharing Scheme Suitable for Cloud Computing

Secret sharing schemes have recently been considered to apply for cloud computing in which many users distribute multiple data to servers. However, when Shamirs (k, n) secret sharing is applied to cloud systems, the amount of share increases more than n times the amount of the secret. Therefore, in this paper we propose a new secret sharing scheme that can reduce the amount of share different from Ramp type secret sharing, suitable for cloud systems, and we prove that it is computationally secure.

Cryptographie key generation from PUF data using efficient fuzzy extractors

Physical unclonable functions (PUFs) and biometrics are inherently noisy. When used in practice as cryptographic key generators, they need to be combined with an extraction technique to derive reliable bit strings (i.e., cryptographic key). An approach based on an error correcting code was proposed by Dodis et al. and is known as a fuzzy extractor. However, this method appears to be difficult for non-specialists to implement. In our recent study, we reported the results of some example implementations using PUF data and presented a detailed implementation diagram. In this paper, we describe a more efficient implementation method by replacing the hash function output with the syndrome from the BCH code. The experimental results show that the Hamming distance between two keys vary according to the key size and information-theoretic security has been achieved.

Information Hiding Method Using Best DCT and Wavelet Coefficients and Its Watermark Competition

In recent years, information hiding and its evaluation criteria have been developed by the IHC (Information Hiding and its Criteria) Committee of Japan. This committee was established in 2011 with the aim of establishing standard evaluation criteria for robust watermarks. In this study, we developed an information hiding method that satisfies the IHC evaluation criteria. The proposed method uses the difference of the frequency coefficients derived from a discrete cosine transform or a discrete wavelet transform. The algorithm employs a statistical analysis to find the best positions in the frequency domains for watermark insertion. In particular, we use the BCH (Bose-Chaudhuri-Hocquenghem) (511,31,109) code to error correct the watermark bits and the BCH (63,16,11) code as the sync signal to withstand JPEG (Joint Photographic Experts Group) compression and cropping attacks. Our experimental results showed that there were no errors in 10 HDTV-size areas after the second decompression. It should be noted that after the second compression, the file size should be less than 1 25 of the original size to satisfy the IHC evaluation criteria.

A Study of Information Hiding Performance Using Simple Dot Pattern with Different Tile Sizes

There are several proposed techniques on the information hiding for printed document. Most of them detect embedded information using directional components which consists of a line element or group of dots. Therefore those techniques have serious problems regarding a visual quality and information capacity. In this paper, we use single dot pattern instead of the line element or group of dots. It is turned out that information capacity is improved for its small amount of dot and compact embedded area. We acquire possible information capacity 50688 bits in business card size with 93.45% information extraction accuracy. This information capacity is more than six times bigger than the conventional technique.

A Zero-Watermarking-Like Steganography and Potential Applications

We propose a new steganographic method which is similar to zero-watermarking. In general, digital steganography and digital watermarking, which both embed secret information in host data, have different intended uses. Digital steganography carries embedded secret information through public networks, and the host data serves only as camouflage. Digital watermarking is used to protect host data by embedding secret information. However, the concept of zero-watermarking was proposed in 2001. It does not embed secret information in host data and a result obtained by the interaction of secret information and host data is registered into a certificate authority for protecting the copyright of host data. Our method is also intended to be included in the concept of zero-watermarking broadly. In this paper, we will clarify the difference of zerowatermarking and our method, evaluate the noise immunity of our method, and discuss with various application possibilities.

Watermarking based on the difference of discrete cosine transform coefficients and an error-correcting code

Digital watermarking has been considered as a solution for copyright protection applications. However, very few researchers have published extensive tests of their algorithms. In recent years, Information Hiding and its Criteria for evaluation (IHC) was developed by the IHC Committee of Japan. In this study, we developed a method that satisfies the IHC evaluation criteria. The proposed method uses a discrete cosine transform and an error-correcting code. In particular, we selected the BCH(511,31,109) code for error correcting the watermark bits and the BCH(63,16,11) code for the sync signal to withstand JPEG compression and cropping attack. The experimental results showed that there were no errors in 10 HDTV-size areas after the second decompression.

Secret sharing scheme for cloud computing using IDs

Secret sharing schemes can be used in cloud computing to allow many participants to distribute multiple data. However, the application of (k, n) secret sharing to cloud systems causes a large increase in storage capacity, making it unsuitable for systems with many secrets to distribute. Moreover, using the ramp scheme to reduce the required storage capacity causes gradual information leakage. Therefore, in this paper, we propose a new secret sharing scheme that is computationally secure and can reduce the number of shares. We compare the proposed method with conventional schemes.

Information Hiding Method Utilizing Low Visible Natural Fiber Pattern for Printed Documents

Digital watermarks provide the capability to add extra information to various media, such as still images, movies and audio, by utilizing features of its content. Several methods for printed document have already been proposed using features of the text or images. In this paper we treat the paper media itself as content and propose a new information hiding methodology which utilizes the fiber pattern of paper. The proposed method is expected to improve the quality of watermarked documents and the geometric sensitivity in the watermarked documents. In this paper we show the principle of the paper-like pattern as a watermark, its possibility, advantages in terms of visual quality and geometric sensitivity.

Asymmetric secret sharing scheme suitable for cloud systems

The asymmetric secret sharing scheme that we proposed at AINA2013 has a feature that reduces the required storage capacity of a specific server. This means that it can be used as the server not only for the entity of a cloud system but also for a device that is managed by a user, such as a smart phone. In this paper, first we propose a new method, which is an AINA method modified such that it is more suitable for application in a cloud system in which multiple users participate, and then, we propose an application to a life log, as an example of a specific application to which this method can be applied.

An Improvement of Robustness Against Physical Attacks and Equipment Independence in Information Hiding Based on the Artificial Fiber Pattern

Digital watermarks provide the capability to insert additional information onto various media, such as still images, movies and audio, by utilizing features of the content. Several methods for printed documents have already been proposed using features of the text or images. In order to overcome the disadvantages of existing methods, we have proposed a new information hiding scheme for printed documents; namely, the artificial fiber pattern by using the features of the paper instead of those of the contents. The method has features of rotational invariance and low visibility. In this paper, we improve the algorithm aimed at equipment independence and the robustness against physical attacks.