Cheonshik Kim

A secure and efficient SIP authentication scheme for converged VoIP networks

Session Initiation Protocol (SIP) has been widely used in current Internet protocols such as Hyper Text Transport Protocol (HTTP) and Simple Mail Transport Protocol (SMTP). SIP is a powerful signaling protocol that controls communications on the Internet for establishing, maintaining and terminating sessions. The services that are enabled by SIP are equally applicable to mobile and ubiquitous computing. This paper demonstrates that recently proposed SIP authentication schemes are insecure against attacks such as off-line password guessing attacks, Denning-Sacco attacks and stolen-verifier attacks. In order to overcome such security problems, a new secure and efficient SIP authentication scheme in a converged VoIP network based on elliptic curve cryptography (ECC) is proposed and it works to exploit the key block size, speed, and security jointly.

Improved modification direction methods

The original exploiting modification direction (EMD) method proposed by Zhang and Wang is a novel data hiding technique which can achieve large embedding capacity with less distortion. The original EMD method can hide (2n+1)-ary numbers by modifying at most one least-significant bit (LSB) of n pixel values. The proposed methods in this paper, 2-EMD and EMD-2, modify at most two pixels of the LSB values. Efficiency of the proposed methods is shown theoretically and through experiments. The 2-EMD and EMD-2 can hide even larger numbers than the EMD with similar distortion under the same conditions. This paper shows that the EMD-2 is much better than the EMD, and slightly better than 2-EMD when n is 3, 4 and 5. The way to generate basis vector can be used for the generalization of the n-EMD and EMD-n where n>1.

Data hiding by an improved exploiting modification direction

This paper represents an improved data hiding scheme, CIE, which uses a codebook to improve the Exploiting Modification Direction (EMD) embedding scheme. In our scheme, one secret (2n + x − 1)-ary digit is hidden in a group of pixels in an image as a modified secret digit. Our proposed scheme has an embedding rate

(N, 1) secret sharing approach based on steganography with gray digital images

R=\log_2(2^{n+x}-1)/n

Data hiding in a halftone image using hamming code (15, 11)

, which is greater than the rate of the EMD scheme, which is R = log2(2n + 1)/n for n ≥ 2 . Embedding rate R is the number of secret bits embedded in each cover pixel. Our experimental results demonstrate that our scheme is able to embed 3 times as many secret bits in an image compared to the original EMD embedding scheme when n = 2 and x = 5. Our scheme has low time complexity and achieves this higher embedding performance while retaining reasonable perceptual quality for the image. An experiment verifies these features of our proposed data hiding scheme.

Aspect ratio invariant visual cryptography by image filtering and resizing

We present a description of a technique to embed secret data to an image, called information hiding or stegnography. We utilize some simple observed relationships between the binary representation of a pixel, the gray code representation, and the utilization of a simple Exclusive-OR operation based upon N images available to the sender and the receiver, called the cover images. We present the algorithms for embedding the secret data in the altered, last image, N+1, called the stego image; as well as extracting this data on the receiving side. We present some experimental images utilizing two cover images, and one stego image and show that the procedure we propose has a high PSNR value, and an almost identical histogram when compared to the before stego image. We also discuss the robustness of this algorithm under attack methods such as steganalysis.

Product control system using rfid tag information and data mining

This paper presents a data hiding technique for a halftone image. Each block of halftone bitmaps is transformed into a sequence of binary bits, and then regarded as a codeword. From the codeword, we can get a syndrome value. The XOR operation between a syndrome and 4- bits secret message is used to conceal 4-bits in the codeword. If the value of a XOR operation is not decimal zero, the position in a codeword should be flipped. In this way, one can hide a message. When every embedding procedure is finished, a sender transmits a stego halftone image to a receiver. A receiver can then extract secret data with a stego image, using a hamming code scheme. Using this procedure, we can conceal secret data in a halftone image and vice versa. Our proposed method is to hide 4-bits in a 4 × 4 block to flip a bit, is easy to implement, and achieves a high embedding capacity with good perceptual quality. It can be used to copyright and secret communications.

Improved Steganographic Embedding Exploiting Modification Direction in Multimedia Communications

In visual cryptographic scheme (VCS), each secret pixel is expanded to m subpixels in shadow images to encrypt a secret image. Apparently, we should put these m subpixels as a rectangle such that the blocks can be arranged compactly with each other. However, if the aspect ratio is viewed as important information of the secret image, the distortion occurs at the case that m is not a square. An aspect ratio invariant VCS (ARIVCS) was accordingly proposed to address the arrangement of subpixels. However, the existing ARIVCSs relied on adding dummy subpixels to the shadow images. In addition, their method needs a mapping pattern that reduces the number of dummy subpixels, but how to design a mapping pattern is a huge challenge. In this paper, we propose an easy solution to construct ARIVCS by image filtering and resizing.

Improving stego image quality in image interpolation based data hiding

In this paper, we suggest a method that applies RFID tag information and a data mining technology to a manufacturing execution system (MES) for efficient process control. The MES is an efficient process control method for many enterprises. But, the MES is not an analysis technique for process control. Therefore, we will supplement a data mining technology and RFID tag information to generate a more efficient process control system. In order to accomplish this, we designed and implemented an efficient product control system and adapted it to a TFT LCD production line using RFID tag information and data mining. As a result, the method proposed solved defects in parts and problems of personnel expenses.

Wear performance of self-mating contact pairs of TiN and TiAlN coatings on orthopedic grade Ti-6Al-4V.

Steganography provides secure communications over the Internet with a cover image. However, it is difficult to transfer many messages with small-sized images. We have improved EMD (Exploiting Modification Direction), proposed by Zhang and Wang, to solve this problem. In this paper, we have developed a (2 n + 2-1)-ary scheme. Our scheme shows a higher embedding rate, R=log2(2 n + 2-1)/n, which is greater than that of the EMD scheme, because the EMD scheme embedding rate is R=log2(2n+1)/n, for n>=2. The experimental results show that our scheme is able to embed twice as many secret bits in multimedia communications compared to the existing EMD embedding method. Our method has low complexity and achieves higher embedding performance with good perceptual quality against the earlier arts. An experiment verified our proposed data hiding method in multimedia communications.