It is proved that if G is a (+1)-colorable graph, so are the graphs G×Pn and C×Cn, where Pn and Cn are respectively the path and cycle with n vertices, and the maximum edge degree of the graph. The exact chromatic numbers of the product graphs and are also presented. Thus the total coloring conjecture is proved to be true for many other graphs.
YANG Yi-xian, LIU Huan-ping (Information Security Center, Department of Information Engineering, Beijing University of Posts and Telecommunications, Beijing 100876, P. R. China )
A technology for combining digital watermarks with two-color bitmap image based on the threshold watermarking method is presented. Our technology doesn't add any thing to the digital media, but combines the watermarks in two-color bitmap image by looking for some characteristic values in the bitmap and uses the relationship between the watermarks and the characteristic values to prove the copyright protection. The choice of the characteristic values depends on the choice of a cryptographic key known by the owner of the bitmap. The benefit of using a cryptographic key is to combine the watermarks with the bitmap in a high secure way.
In this paper, we propose a novel Unequal Error Protection (UEP) scheme with two levels for image transmission using Multilevel Codes (MLC). By providing the best protection for the most important data, the final recovered image quality is remarkably improved both in visual effect and in Peak Signal to Noise power Ratio (PSNR) performance.
LI Zuo-wei~1, YANG Yi-xian~1, YUAN Dong-feng~2, HU Zheng-ming~1 1.Information Security Center,Beijing University of Posts and Telecommunications, Beijing 100876, P.R. China
After extending the forgery attacks to Nyberg-Rueppel’s signatures with message recovery, Atsuko Miyaji in 1997 proposed two suitable message recovery signatures, (F1) and (F2). In this paper, another new forgery attacks to (F1), (F2) and Nyberg-Rueppel’s signatures are presented.
Li Zichen Li Zhongxian Yang Yixian , Wu Weilin (PO Box 126, Information Security Center, Beijing Univ. of Posts and Telecom., Beijing 100876)
How to distribute a secret key information to n authorized departments, denoted as: S1, S2,…, Sn, respectively. For every autherized department Si(i = 1,2,… ,n), there are qi authorized persons, and every authorized person has the same secret key information as that of any other authorized persons in the same authorized department. The secret key information can be reconstructed completely from the secret key information of any k authorized persons, if there is at least one authorized person included for every authorized department. But other cases, the secret key information cannot be reconstructed completely. In this paper, based on the algebraic semigroup theory, a secret key sharing scheme is proposed, which can satisfy the demand.
Wang Yongchuan Li Zichen Yang Yixian (Info. Security Centre of Beijing Univ. of Posts and Telecomm., P. O. Box 126, Beijing 100876)
