新型文本信息隐藏算法研究

发布时间：2019-07-01 17:17

【摘要】：信息隐藏是一门通过迷惑性的手段在无害的载体数据中嵌入秘密信息的科学与艺术。它要求嵌入过程对载体造成的失真是不可感知的。信息隐藏既是一门古老的技术,也是一门年轻的学科。曾在古希腊和罗马战争时期被军队广泛应用于实现安全通信,但之后逐渐边缘化。直到互联网技术发展起来以后,信息隐藏才真正被关注并获得广泛的研究。加密技术过去被认为足以保护人们通信的安全。加密技术只阻止了未被授权的人对信息的读取,但加密后的乱码数据暴露了信息本身的重要性反而更容易引起拦截者针对性的监视和攻击。不同于密码学,信息隐藏的目的在于隐藏秘密信息存在的事实,从而避免引起拦截者的注意力。但是信息隐藏并不是用来取代加密技术的,通过对两者的结合使用往往能实现更安全的保护。常被用作信息隐藏载体的有文本、图像、视频、音频、网络协议数据单元等。图像、视频等多媒体数据由于其本身冗余空间大,对修改不敏感的特性,相关的研究成果较丰富,而文本受限于嵌入难度大,系统鲁棒性差和自然语言处理技术的发展不成熟,针对文本的信息隐藏和检测算法的研究收到的关注较少。尽管使用文本作为信息的载体受到诸多的限制,但在开放的互联网环境中,文本的应用更加广泛,且攻击者的在注意力不在文本上,研究基于文本的信息隐藏算法具有广阔的应用前景。因此,设计一个隐蔽性更好、嵌入率更高、鲁棒性更好的算法成为科研人员急需解决的问题。我们在本文中主要做了以下工作:1)对基于不可见字符的隐藏算法进行安全性分析,给出了一个简单的检测方法。该方法能够对目前基于不可见字符的隐藏算法中的秘密信息进行有效的检测;在最新的Unicode标准中发现了一些新的可用于不可见字符隐藏算法的字符,以此增大算法嵌入率和躲避目前针对常用不可见字符的检测算法。2)提出了一种基于新的不可见字符和哈希函数的文本信息隐藏算法。算法有效利用了不可见字符和哈希函数,算法在执行嵌入过程前对秘密信息进行了分段和奇偶编码,秘密信息将以块为单位进行嵌入。算法在安全性,嵌入率上有较好的表现。3)利用哈希函数中存在的哈希碰撞现象,定义了奇碰撞和偶碰撞概念,并实现了将一个发生碰撞的文本分段的嵌入容量转移给其后一个分段(而不是浪费这个容量),增强了算法的嵌入率和安全性。
[Abstract]:Information hiding is a science and art of embedding secret information into harmless carrier data by confusing means. It requires that the distortion caused by the embedding process to the carrier is imperceptible. Information hiding is not only an ancient technology, but also a young subject. It was widely used by the army to achieve secure communication during the ancient Greek and Roman wars, but then gradually marginalized. It was not until the development of Internet technology that information hiding was really concerned and widely studied. Encryption technology used to be considered sufficient to protect the security of people's communications. Encryption technology only prevents unauthorized people from reading the information, but the encrypted random code data exposes the importance of the information itself, but it is more likely to cause targeted surveillance and attack by interceptors. Different from cryptography, the purpose of information hiding is to hide the fact that secret information exists, so as to avoid attracting the attention of interceptors. However, information hiding is not used to replace encryption technology, through the combination of the two can often achieve more secure protection. Text, image, video, audio, network protocol data unit and so on are often used as information hiding carriers. Image, video and other multimedia data are rich in related research results because of their large redundant space and insensitive to modification, while text is limited to embedding, poor system robustness and immature development of natural language processing technology, and less attention has been paid to the research of text information hiding and detection algorithms. Although the use of text as the carrier of information is limited, but in the open Internet environment, the application of text is more extensive, and the attacker's attention is not on the text, so the research on text-based information hiding algorithm has a broad application prospect. Therefore, the design of an algorithm with better concealment, higher embedding rate and better robustness has become an urgent problem for researchers to solve. In this paper, we mainly do the following work: 1) the security analysis of the hidden algorithm based on invisible characters is carried out, and a simple detection method is given. This method can effectively detect the secret information in the current invisible character hiding algorithm, and find some new characters that can be used in the invisible character hiding algorithm in the latest Unicode standard, so as to increase the embedding rate of the algorithm and avoid the current detection algorithm for common invisible characters. 2) A text information hiding algorithm based on new invisible characters and hash functions is proposed. The algorithm makes effective use of invisible characters and hash functions. Before the embedding process, the algorithm segment and odd-even code the secret information, and the secret information will be embedded in blocks. The algorithm has a good performance in security and embedding rate. 3) the concepts of odd collision and even collision are defined by using the hash collision phenomenon in hash function, and the embedding capacity of a collided text segment is transferred to the next segment (instead of wasting this capacity), which enhances the embedding rate and security of the algorithm.
【学位授予单位】：安徽大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TP309

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