以图像为载体的最大意义位(MSB)信息隐藏技术的研究

加密技术是保障通信安全的一种重要手段,然而信息经过加密后容易引起攻击者的好奇和注意,容易遭到攻击和破坏.为解决这一问题,就要把加密技术与信息隐藏技术结合起来,即把经过加密的信息作为待隐藏信息,加载到载体文件(本文采用网上常用的彩色图像文件)中传播.只要做到隐藏信息加载前后,载体图像的视觉效果的变化不能被人眼察觉即可.目前已知的用于信息保密的信息隐藏技术可分为两种,第一种是基于频域的信息隐藏技术,如扩频隐藏、DCT隐藏、子波隐藏技术等,若以彩色图像为宿主,则此类技术主要利用人眼对高空间频率分量上噪声不敏感的特点将待隐藏信息编码到图像的高频分量,以实现信息隐藏的目的,一般地,此类技术较难实现大数据量隐藏;第二种技术为空域隐藏技术,其典型做法是将待隐藏信息编码隐藏到宿主的最小意义位(LSB)上,由于其信息隐藏位置对图像的影响不大,因此安全性不高.本文提供了一种在空域中,利用图像像素数据的最高位实现信息隐藏的方法.本方法利用颜色量化技术对图像颜色进行归并,然后按照特定的格式存储,产生冗余空间,最后把待隐藏信息装载入冗余空间.该方法不仅能实现大数据量的信息隐藏,而且信息隐藏的位置是图像的最大意义位,这就使得信息隐藏的安全性比以往的最小意义位(LSB)信息隐藏技术有了更大的提高.

Study of the MSB information-hiding technique in a carrier image

Encryption technique is an important method to ensure safe communication, but it has a shortcoming. Because the files encrypted are vulnerable to attackers, they may be destroyed.To solve the problem, the authors take advantages of the encryption technique and information_hiding technique, i.e. concealing the information encrypted into a carrier file. The authors adopts color image files being used in the Internet. If human eyes can not observe the diversifications of the carrier image before and after hiding, the method can be very safe.As far as the authors know, there are two kinds of encryption techniques. One is based on frequency region, such as expanding frequency hiding, DCT hiding and sub_wave hiding, etc. By these methods the information is concealed into the high frequency heft of the carrier image code, which can not be observed by human eyes. Generally speaking, not much data can be concealed into a carrier image. The other is based on space region, a typical method to conceal information in the least significance bits (LSB); however, due to their unsafety, they are not important to the carrier image. This paper provides a method that can create redundant space in a color image by color quantization and hiding information in the MSB of the image. The method is better than that in LSB since the MSB is very important to the visual effect of the image.