Computer Engineering and Applications ›› 2010, Vol. 46 ›› Issue (6): 160-162.DOI: 10.3778/j.issn.1002-8331.2010.06.046

• 图形、图像、模式识别 • Previous Articles     Next Articles

Visual cryptographic scheme with sub-block coding method

LIN Ke-zheng,FAN Bo,YANG Wei   

  1. College of Computer Science & Technology,Harbin University of Science and Technology,Harbin 150080,China
  • Received:2008-09-10 Revised:2008-11-10 Online:2010-02-21 Published:2010-02-21
  • Contact: LIN Ke-zheng

基于分块字典的可视密码改进方法

林克正,范 波,杨 微   

  1. 哈尔滨理工大学 计算机科学与技术学院,哈尔滨 150080
  • 通讯作者: 林克正

Abstract: In order to avoid pixel expansion and contrast of the gathered secret image compromise,a new visual cryptographic scheme,which is called visual cryptographic scheme with sub-block coding method,is presented.Instead of taking m subpixels to represent one pixel,the share image is divided into sub-blocks with same size,each of which is taken as a unit to encode and with same pixel size.Then sub-block coding method is adopted to convert each shadow image to numbers matrix,that is,every sub-block meets a number.After that,according to a secret key,these two number matrices are converted into a series of number.Last the series is encrypted to transport or do some other operations.This scheme is compared to the (k,n) visual secret sharing scheme in section 4 and it shows that there do not exist pixel expansion and contrast compromise in this new scheme.

Key words: visual cryptographic scheme, sub-block coding, pixel expansion

摘要: 针对目前可视密码术引起的像素膨张、与原密图相比,叠合图像的亮度、对比度降低问题,提出一种新的基于分块字典的可视密码改进方法。该方法首先根据确定大小的像素分块,列举每个子图各子块像素分布情况后建立相应的分块字典,并对分块字典条目进行编号;然后对原密图置乱后,将原密图分成两个子密图;再分别两个子密图进行均匀分割,将其分成若干子块,所有密图子块对应一个字典编号并进行一维化,则得出由两个子图所有子块编号组成的序列。由此,密图就由这个分块字典编号序列所确定,经过传输后,提取并组成字典编号序列,二维还原后与相应的分块字典条目对应,装配得出两个子图叠合后还原成原密图。与以前的可视密码算法,如(k,n)门限方案等相比,采用子图交错叠合、基于分块字典的可视密码改进方法,可减少算法复杂度,编码的比特序列长度是对原密图直接编码后的比特序列长度的两倍,从而减少像素膨胀,也不会引起叠合图像的亮度、对比度降低的问题。从而更具实用性。

关键词: 可视密码, 分块字典, 像素膨胀

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