"签名的签名"技术研究

本文探讨了"签名的签名"技术。针对签名图像的特点,对二值图像水印嵌入方法和灰度图像水印嵌入方法进行了研究,建立了二值图像的像素可翻转值查找表,给出了签名图像的4级灰度表示法。实验结果表明,本文给出的基于4级灰度的LSB水印嵌入方法具有嵌入容量大,不可见性好,简单易行等特点。     

微机辅助印文鉴别系统的设计

利用微机进行印章等图像鉴别比较的软硬件系统,可用于印章、车票、发票等方面的鉴别.     

算法化"主体":组织抑或契约?

传统民商法组织理论面临多元发展需求与信息技术的挑战.在通证经济中,区块链网络参与者借助分布式记账技术,形成了根植于智能合约、以共识算法为治理机制的算法化主体.算法化主体不具备法人的科层治理结构,也不符合商业信托的法律构造,若将其界定为合伙或合伙企业,将使通证持有成员陷入互负连带责任的困境,不利于加密财产的交易.因此,研究算法化主体的技术构造,引入制度经济学以治理为核心对组织与契约关系进行讨论成为选择.共识算法去除了传统组织的科层机制,智能合约克服了不完全契约的局限,分布式记账与加密技术等区块链融合技术生态支撑了算法化主体客观性的交易特征,使得算法化主体具有动态性的组织特征.可将算法化主体认定为民法典上的非法人组织,适用民法典第104条与未来特别规定解决其责任归属问题.     

活体指纹图像质量自动评估的参数选择与实现

1前言随着计算机技术、信号信息处理和模式识别技术的乱,难以准确提取到中心点,而且为了提高比对精度,多数指纹算法对于模糊区在匹配时不参与比对。因此,模糊区域多或清晰区域少,都表明指纹质量差。2.1灰度均值和方差下式用于计算指纹灰度均值M和灰度方差Var,图像大小为N×N,G(i,j)是指纹图像第i行第j列的图像元素的灰度值。M=1N2∑N-1j=0∑N-1i=0G(i,j);VAR=1N2∑N-1j=0∑N-1i=0[G(i,j)-M]22.2均衡化均衡化是降低指纹脊线和谷线间的灰度偏差,调刑事技术2007年第6期整指纹灰度均值和方差接近给定的期望均值M0和期望方差Var0,均衡化…     

“同版“印章的实验研究

制作了13枚"同版"渗透型印章和激光雕刻印章,分析了这些"同版"印章的印面特征和盖印印文特征.研究发现,相同条件下制作的"同版"印章的个体差异十分微小,如果考虑到各种盖印条件下,这些印章盖印印文特征的变化范围,"同版"印章印文的检验是十分困难的,甚至是不可能的.     

算法商业秘密与算法正义

算法时代中,"算法黑箱""算法歧视"和"算法茧房"等非正义现象引发了算法规制的需要.但算法商业秘密的存在使算法处于"黑箱"之中,成为算法正义实现的障碍.面对算法商业秘密与算法正义的张力可以从三个角度加以考量:商业秘密的公共利益平衡;算法知情同意权、算法解释权和算法拒绝权等私权制约;算法正当程序.由于对商业秘密的公共利益考量主要局限于维系商业道德和市场秩序,无法实现对算法商业秘密的有效制约.算法私权中基于一般道德和法理的算法拒绝权能够成为制衡算法商业秘密的强理由,同时,算法正义需要建构一种基于过程的,而不是仅基于结果的正当程序观念.     

基于直方图均衡化算法的数字电视画面亮度保持技术研究

本文针对直方图均衡化算法进行了详细的算法分析,得出该算法非常适合针对数字电视图像进行增强清晰度的预处理.基于此,笔者对直方图均衡化算法在数字电视画面亮度保持中的算法技术进行了初步研究.     

同源光敏印章印文鉴别方法的研究

目前伪造同源光敏印章印文的案件已呈上升趋势.通过对同源光敏印章制作原理、工艺过程及盖印过程等方面进行实验研究,找出了同源印章印文之间的差异,总结出了同源光敏印章印文的特点、鉴别方法及检验注意事项,可为鉴别此类案件提供可靠的依据.     

铜导线一次和二次短路熔痕的显微共聚焦激光拉曼光谱特征研究

目的 为了判定火灾发生的原因,依据激光拉曼光谱(RMS)能够反映出经过不同高温热处理炭材料的石墨化程度,以此来探索电气短路判定的技术依据.方法 利用显微共聚焦激光拉曼光谱仪对火灾中不同环境下生成的铜导线短路熔痕表面碳痕斑进行检测分析,利用碳痕斑两个拉曼特征位移峰的比值,计算不同短路熔痕表面碳化斑的石墨化度.结果 铜导线的一次短路、二次短路和火烧熔痕上残留碳斑石墨化度不同,一次短路熔珠碳痕的石墨化度R值最小,火烧熔痕的石墨化度R值最大.结论 该研究建立了显微激光拉曼光谱法无损检测分析铜导线短路熔痕的新方法.     

算法私人执法对版权公共领域的侵蚀及其应对

利用“通知—移除”规则以网络服务商代替公权力机构居中处理侵权纠纷被视为版权领域的私人执法。随着算法技术的应用,版权领域的私人执法模式从人工操作转向全程算法化,表现为查找侵权行为算法化、发送侵权通知算法化、处置侵权信息算法化、预防侵权发生算法化。私人执法算法化在极大提高执法效率的同时,也造成了对版权公共领域的侵蚀,主要表现为压缩“个人使用”空间、剥夺“适当引用”机会、阻碍“科学研究”开展、架空用户“反通知”权利等。造成上述负面后果的根源在于侵权认定的复杂性与算法技术的局限性以及利益驱动下算法执法机制被滥用。可以从以下4个方面来应对算法的私人执法对版权公共领域的侵蚀,即将版权公共领域考量植入算法设计中、在特殊情形下以人工审查辅助算法执法、完善过滤机制下的用户申诉程序、针对恶意通知行为规定惩罚性赔偿责任。     

A robust detection algorithm for copy-move forgery in digital images

With the availability of the powerful editing software and sophisticated digital cameras, region duplication is becoming more and more popular in image manipulation where part of an image is pasted to another location to conceal undesirable objects. Most existing techniques to detect such tampering are mainly at the cost of higher computational complexity. In this paper, we present an efficient and robust approach to detect such specific artifact. Firstly, the original image is divided into fixed-size blocks, and discrete cosine transform (DCT) is applied to each block, thus, the DCT coefficients represent each block. Secondly, each cosine transformed block is represented by a circle block and four features are extracted to reduce the dimension of each block. Finally, the feature vectors are lexicographically sorted, and duplicated image blocks will be matched by a preset threshold value. In order to make the algorithm more robust, some parameters are proposed to remove the wrong similar blocks. Experiment results show that our proposed scheme is not only robust to multiple copy-move forgery, but also to blurring or nosing adding and with low computational complexity.     

Pinpoint authentication watermarking based on a chaotic system

Watermarking technique is one of the active research fields in recent ten years, which can be used in copyright management, content authentication, and so on. For the authentication watermarking, tamper localization and detection accuracy are two important performances. However, most methods in literature cannot obtain precise localization. In addition, few researchers pay attention to the problem of detection accuracy. In this paper, a pinpoint authentication watermarking is proposed based on a chaotic system, which is sensitive to the initial value. The approach can not only exactly localize the malicious manipulations but reveal block substitutions when Holliman-Memon attack (VQ attack) occurs. An image is partitioned into non-overlapped regions according to the requirement on precision. In each region, a chaotic model is iteratively applied to produce the chaotic sequences based on the initial values, which are determined by combining the prominent luminance values of pixels, position information and an image key. Subsequently, an authentication watermark is constructed using the binary chaotic sequences and embedded in the embedding space. At the receiver, a detector extracts the watermark and localizes the tampered regions without access to the host image or the original watermark. The precision of spatial localization can attain to one pixel, which is valuable to the images observed at non-ordinary distance, such as medical images and military images. The detection accuracy rate is defined and analyzed to present the probability of a detector making right decisions. Experimental results demonstrate the effectiveness and advantages of our algorithm.     

Forged seal detection based on the seal overlay metric

This paper describes a method for verifying the authenticity of a seal impression imprinted on a document based on the seal overlay metric, which refers to the ratio of an effective seal impression pattern and the noise in the neighborhood of the reference impression region. A reference seal pattern is obtained by taking the average of a number of high-quality impressions of a genuine seal. A target seal impression to be examined, often on paper with some background texts and lines, is segmented out from the background by an adaptive threshold applied to the histogram of color components. The segmented target seal impression is then spatially aligned with the reference by maximizing the count of matching pixels. Then the seal overlay metric is computed for the reference and the target. If the overlay metric of a target seal is below a predetermined limit for the similarity to the genuine, then the target is classified as a forged seal. To further reduce the misclassification rate, the seal overlay metric is adjusted by the filling rate, which reflects the quality of inked pattern of the target seal. Experiment results demonstrate that the proposed method can detect elaborate seal impressions created by advanced forgery techniques such as lithography and computer-aided manufacturing.     

利用ImageXpress系统灰度特征区分激光打印复印一体机的打印及复印文件初探

目的探索区分激光打印复印一体机的打印文件及复印文件的方法。方法利用ImageXpress系统对理光MP4000BSP激光打印复印一体机的打印文件和复印文件进行灰度特征值的测量。结果两种文件的灰度平均值的平均值和95%置信区间存有明显的差异,且这种差异较为稳定：打印件的平均值约为50,而复印件约为53;打印件的95%置信区间介于50和51.5之间,而复印件的置信区间介于52.5与54之间。结论本方法通过量化对激光打印复印一体机打印及复印文件进行区分是可行的。     

傅立叶显微红外化学成像在朱墨时序鉴定中的应用研究

目的建立朱墨时序的傅里叶显微红外成像检验方法。方法根据印文及油墨的红外光谱特征峰,使用傅立叶变换红外（FTIR）成像系统直接对纸张上印文及文字油墨进行化学成像,根据成像特征从而判断朱墨时序。结果先打印后盖章的红外成像中油墨字迹的红外成像不完整,有被印章所覆盖的痕迹,而印章的红外成像完整,在字迹中可见印章成像斑点。先盖章后打印的红外成像中油墨字迹的红外成像完整,没有被印章所覆盖,而印章的红外成像不完整,被字迹的油墨所覆盖。结论该方法较传统的鉴定方法更加快速、简单,可以更加直观的反映行文顺序,并且具有不破坏检验样本的特点。     

JPEG steganography detection with Benford's Law

In this paper we present a novel approach to the problem of steganography detection in JPEG images by applying a statistical attack. The method is based on the empirical Benford's Law and, more specifically, on its generalized form. We prove and extend the validity of the logarithmic rule in colour images and introduce a blind steganographic method which can flag a file as a suspicious stego-carrier. The proposed method achieves very high accuracy and speed and is based on the distributions of the first digits of the quantized Discrete Cosine Transform coefficients present in JPEGs. In order to validate and evaluate our algorithm, we developed steganographic tools which are able to analyse image files and we subsequently applied them on the popular Uncompressed Colour Image Database. Furthermore, we demonstrate that not only can our method detect steganography but, if certain criteria are met, it can also reveal which steganographic algorithm was used to embed data in a JPEG file.     

A Simple Computer‐assisted Quantification of Contrast in a Fingerprint

A simple method for quantification of contrast in a fingerprint is proposed. Contrast is defined as the average difference in intensity of pixels between valleys and ridges in a fingerprint. It is quantified from a scanner‐acquired image of the fingerprint using a histogram function of Adobe Photoshop. The method was validated with black inked prints and marks developed with aluminum powder. Moreover, we tested resistance of the method to rater‐dependent errors and dependence of the measurements on the resolution of an image and the model of the scanner. For both groups of fingerprints, the method gave coherent and easily interpretable quantitative values for contrast. There were no significant differences between measurements performed by different raters and by the same rater in a test–retest procedure. However, the method was found to be instrument dependent, as measurements were significantly affected by image resolution and the model of the scanner.     

Distributed password cracking with BOINC and hashcat

Considering today's challenges in digital forensics, for password cracking, distributed computing is a necessity. If we limit the selection of password-cracking tools strictly to open-source software, hashcat tool unambiguously wins in speed, repertory of supported hash formats, updates, and community support. Though hashcat itself is by design a single-machine solution, its interface makes it possible to use the tool as a base construction block of a larger distributed system. Creating a “distributed hashcat” which supports the maximum of hashcat's original features requires a smart controller that employs different distribution strategies in different cases. In the paper, we show how to use BOINC framework to control a network of hashcat-equipped nodes and provide a working solution for performing different cracking attacks. We also provide experimental results of multiple cracking tasks to demonstrate the applicability of our approach. Last but not least, we compare our solution to an existing hashcat-based distributed tool - Hashtopolis.     

Determination of the sequence of intersecting lines from laser toner and seal ink by Fourier transform infrared microspectroscopy and scanning electron microscope / energy dispersive X-ray mapping

The aim of this study was to verify that the combination of Fourier transform infrared microspectroscopy and scanning electron microscope / energy dispersive X-ray mapping could be applied to line intersection problems. The spectral data of red seal ink, laser toner and their intersections, such as peak location and peak intensity, were described. Relative peak height ratios of different chemical components in intersecting lines were used to distinguish the sequences. Energy dispersive X-ray mapping characteristics of intersecting areas were also detailed. The results show that both the laser toner and the seal ink appear on the surface of intersections, regardless of the sequence. The distribution of the two inks on the surface is influenced not only by the sequence of heterogeneous lines but also by diffusion. Fourier transform infrared microspectroscopy and scanning electron microscope/energy dispersive X-ray mapping are able to explore the chemical components and the corresponding elemental distribution in the intersections. The combination of these two techniques has provided a reliable method for sequencing intersecting lines of red seal ink and laser toner, and more importantly, this method may be a basis for sequencing superimposed lines from other writing instruments.