Shoko Imaizumi

Partial-scrambling of images encoded using JPEG2000 without generating marker codes

A method is described for efficient partial-scrambling of JPEG2000 images that avoids generating marker codes and improves the ability to control the degree, strength, and computational complexity of scrambling. This higher control ability is due to the use of a parameter. This parameter also controls the scrambling time, an important consideration for real-time processing.

Generalized hierarchical encryption of JPEG 2000 codestreams for access control

This paper proposes an encryption scheme maintaining hierarchy of JPEG 2000 codestreams for flexible access control. JPEG 2000 generates hierarchical codestreams and has flexible scalability, such as, SNR, space, or color components. In a proposed method, only one managed key (master key) exists, and for a user permitted to access a reserved image quality, only one key generated by the master key is delivered. Also, a different key generated by the master key is delivered for a user permitted to access a different quality. The proposed access control method is available for all kinds of JPEG 2000 scalability. On the other hand, some conventional methods need several keys to control image quality. Another conventional method is not suitable for JPEG 2000 scalability.

Collusion Attack-Resilient Hierarchical Encryption of JPEG 2000 Codestreams with Scalable Access Control

This paper proposes a collusion attack-resilient method of encryption for access control of JPEG 2000 codestreams with hierarchical scalabilities. The proposed method generates one encryption key from one single key by multi-dimensional scanning to serve encryption keeping the scalability of codestrems. To avoid collusion attacks in which multiple users generate an illegal key from their own keys to overcome the access control, sufficient conditions are considered in this method. Moreover, a skip encryption is introduced to decrease the computational complexity and key management-and-de-livery cost of encryption. Simulation results show the effectiveness of the proposed method.

A Robust Identification Scheme for JPEG XR Images with Various Compression Ratios

A robust scheme for identifying JPEG XR coded images is proposed in this paper. The aim is to identify the images that are generated from the same original image under various compression ratios. The proposed scheme is robust against a difference in compression ratios, and does not produce false negative matches in any compression ratio. A new property of the positive and negative signs of lapped biorthogonal transform coefficients is considered to robustly identify the images. The experimental results show the proposed scheme is effective for not only still images, but also video sequences in terms of the querying such as false positive, false negative and true positive matches.

Efficient collusion attack-free access control for multidimensionally hierarchical scalability content

This paper proposes an efficient access control method for content with multiple dimensions of hierarchical scalability. The proposed method versatilely serves various quality content by simultaneous control in every dimensions of scalability. This method manages single entity for the content and single encipher key, though it prevents users from colluding. A user receives single ciphered content and single decipher key to obtain the content with the permitted quality. In comparison to the conventional collusion attack-resistant access control methods, the sophisticated key generation manner in the proposed method reduces the required length of the managed key and that of the managed codestream.

An efficient access control method for composite multimedia content

This paper proposes an access control method for composite multimedia content in which only a single key is delivered to a user. The proposed method simultaneously controls access to each medium in one composite multimedia content in which a medium can be hierarchically encoded. This method introduces recursive hash chains for key generation so that the number of delivered key is reduced to one, whereas the conventional method having the above mentioned features has to deliver multiple keys to a user. The managed key in the proposed method is also reduced to one.

A key derivation scheme for hierarchical access control to JPEG 2000 coded images

This paper proposes a key derivation scheme to control access of JPEG 2000 (JP2) coded images, which consist of hierarchical scalability such as SNR, resolution levels, and so on. The proposed scheme simultaneously controls access to each level of scalability. The proposed scheme derives keys through hash chains, and each JP2 packet is enciphered with each individual key. By introducing combinations of a cyclic shift and a hash function, the proposed scheme manages only a single key for a JP2 image; whereas the conventional access control schemes having the above mentioned features manage multiple keys. The single managed key is not delivered to any user. The proposed scheme is also resilient to collusion attacks. Performance analysis shows the effectiveness of the proposed scheme.

Multibit Embedding Algorithm for Steganography of Palette-Based Images

We propose a high-capacity data hiding scheme for palette-based images that does not seriously degrade the image quality in this paper. The proposed scheme can embed a multiple-bit message within the unit of a pixel matrix by using Euclidean distance, while some conventional schemes can embed only a one-bit message per pixel. The stego-images created by using our scheme offer a better quality compared to those by the conventional scheme. Moreover, we have obtained these results with low implementation cost. The experimental results show that the proposed scheme is efficient.

Improvement of Multi-bit Information Embedding Algorithm for Palette-Based Images

We propose a new approach that is an improvement on the conventional of a multi-bit information embedding algorithm for palette-based images. The proposed method embeds secret information by changing the pixel values for each of the