On-line signature verification system with failure to enrol management

In this paper we introduce a new biometric verification system based on on-line signatures and simulate its operation. For this purpose we have split the MCYT signature database in three subsets: one for classifier training, another for system adjustment and a third one for system testing simulating enrolment and verification. This context corresponds to a real operation, where a new user tries to enrol an existing system and must be automatically guided by the system in order to detect the failure to enrol (FTE) situations. The main contribution of this work is the management of FTE situations by means of a new proposal, called intelligent enrolment, which consists of consistency checking in order to automatically reject low quality samples. This strategy enhances the performance of the system to 22% when 8% of the users are left out. In this situation 8% of the people cannot be enroled in the system and must be verified by other biometrics or by human abilities. These people are identified with intelligent enrolment and the situation can be thus managed. In addition we also propose a DCT-based feature extractor with threshold coding and discriminability criteria.     

On-line signature recognition based on VQ-DTW

This paper studies some pattern recognition algorithms for on-line signature recognition: vector quantization (VQ), nearest neighbor (NN), dynamic time warping (DTW) and hidden Markov models (HMM). We have used a database of 330 users which includes 25 skilled forgeries performed by five different impostors. This database is larger than the typical ones found in the literature.Experimental results reveal that our first proposed combination of VQ and DTW (by means of score fusion) outperforms the other algorithms (DTW, HMM) and achieves a minimum detection cost function (DCF) value equal to 1.37% for random forgeries and 5.42% for skilled forgeries. In addition, we present another combined DTW-VQ scheme which enables improvement of privacy for remote authentication systems, avoiding the submission of the whole original dynamical signature information (using codewords, instead of feature vectors). This system achieves similar performance than DTW.     

HMM-based on-line signature verification: Feature extraction and signature modeling

A function-based approach to on-line signature verification is presented. The system uses a set of time sequences and Hidden Markov Models (HMMs). Development and evaluation experiments are reported on a subcorpus of the MCYT bimodal biometric database comprising more than 7000 signatures from 145 subjects. The system is compared to other state-of-the-art systems based on the results of the First International Signature Verification Competition (SVC 2004). A number of practical findings related to feature extraction and modeling are obtained.     

On-line signature verification using vertical signature partitioning

In this paper we propose a new approach to identity verification based on the analysis of the dynamic signature. Considered problem seems to be particularly important in terms of biometrics. Effectiveness of signature verification significantly increases when dynamic characteristics of the signature are considered (e.g. velocity, pen pressure, etc.). These characteristics are individual for each user and difficult to forge. The effectiveness of the verification on the basis of an analysis of the dynamics of the signature can be further improved. A well-known way is to consider the characteristics of the signature in the sections called partitions. In this paper we propose a new method for identity verification which uses partitioning. Partitions represent time moments of signing of the user. In the classification process the partitions, in which the user created more stable reference signatures during acquisition phase, are more important. Other important features of our method are: using capabilities of fuzzy set theory and development on the basis of them the flexible neuro-fuzzy systems and interpretable classification system for final signature classification. In this paper we have included the simulation results for the two currently available databases of dynamic signatures: free SVC2004 and commercial BioSecure database.     

一类基于超椭圆曲线密码的批验证签名方案

分析了现有批验证签名方案秘密信息泄漏、签名伪造等安全漏洞以及协议过程复杂、签名认证运算开销大等不足之处。基于超椭圆曲线密码提出了一类批验证签名方案,该方案由交互式与非交互式批验证签名协议组成;方案充分发挥了超椭圆曲线密码系统密钥量小、效率高的优势,其协议与算法安全、简洁、高效,降低了软硬件实现的系统开销,可广泛应用于计算机与无线通信等网络环境。     

Off-line signature verification by the tracking of feature and stroke positions

There are inevitable variations in the signature patterns written by the same person. The variations can occur in the shape or in the relative positions of the characteristic features. In this paper, two methods are proposed to track the variations. Given the set of training signature samples, the first method measures the positional variations of the one-dimensional projection profiles of the signature patterns; and the second method determines the variations in relative stroke positions in the two-dimension signature patterns. The statistics on these variations are determined from the training set. Given a signature to be verified, the positional displacements are determined and the authenticity is decided based on the statistics of the training samples. For the purpose of comparison, two existing methods proposed by other researchers were implemented and tested on the same database. Furthermore, two volunteers were recruited to perform the same verification task. Results show that the proposed system compares favorably with other methods and outperforms the volunteers.     

基于门限的无可信中心的盲签名方案*

提出了一种新的无须可信中心的门限盲签名方案。方案基于Shamir 秘密共享方案而构建。签名过程分为三个阶段,即系统初始化、部分签名的生成和验证阶段、系统签名的生成和验证阶段。为了保证分布性,方案无须可信中心的参与,并且部分签名的生成、系统签名的生成和验证均可以方便地实现。通过对方案的安全性分析显示,部分签名和系统签名都是不可伪造的,并且在整个签名过程中都没有秘密信息的泄露,方案本身的安全性和高效性使得此方案具有较高的实用性。     

Security reconsideration of the Huang-Wang nominative signature

To prevent potential misuse and to enhance privacy, signatures with restricted verifiability have been recently extensively discussed in the literature. Unlike undeniable signatures and designated verifier signatures, nominative signatures restrict the ability of signature verification and confirmation to a designated verifier only. In this paper, security issues of a nominative signature scheme proposed by Huang and Wang are reconsidered. The first result obtained is that the cryptanalysis reported recently by Susilo and Mu is shown to be incompletely correct; namely, the nominator in fact cannot verify but can only screen signatures, and therefore any third party should not be convinced by the confirmation done by the nominator. The second observation is that the scheme proposed by Huang and Wang may not be as strong as originally claimed. Nevertheless, the overall result is optimistic that the security properties provided by the Huang-Wang nominative signature scheme are sufficient for most applications.     

The practicality of text signatures for accelerating string searching

This paper studies the use of text signatures in string searching. Text signatures are a coded representation of a unit of text formed by hashing substrings into bit positions which are, in turn, set to one. Then instead of searching an entire line of text exhaustively, the text signature may be examined first to determine if complete processing is warranted. A hashing function which minimizes the number of collisions in a signature is described. Experimental results for two signature lengths with both a text file and a program file are given. Analyses of the results and the utility and application of the method conclude the discussion.     

Drift-correcting template update strategy for precision feature point tracking

In this paper we present a drift-correcting template update strategy for precisely tracking a feature point in 2D image sequences. The proposed strategy greatly complements one of the latest published template update strategies by incorporating a robust non-rigid image registration step. Previous strategies use the first template to correct drifts in the current template; however, the drift still builds up when the first template becomes different from the current one particularly in a long image sequence. In our strategy the first template is updated timely when it is revealed to be quite different from the current template and henceforth the updated first template is used to correct template drifts in subsequent frames. Our method runs fast on a 3.0 GHz desktop PC, using about 0.03 s on average to track a feature point in a frame (under the assumption of a general affine transformation model, 61 × 61 pixels in template size) and less than 0.1 s to update the first template. The proposed template update strategy can be implemented either serially or in parallel. Quantitative evaluation results show the proposed method in precision tracking of a distinctive feature point whose appearance is constantly changing. Qualitative evaluation results show that the proposed method has a more sustained ability to track a feature point than two previous template update strategies. We also revealed the limitations of the proposed template update strategy by tracking feature points on a human’s face.     

改进VDDTW的在线手写签名认证算法

在线手写签名认证是一种基于生物特征的身份认证技术。将VDDTW算法应用于在线手写签名认证,该算法改进了DTW中局部匹配距离的计算方法,考虑了时间序列局部曲线的变化趋势,使得时间序列的局部点到点的对正更加合理。在采用有训练的伪造样本的情况下,对累积匹配距离进行时间加权,加大了真伪签名的区分度。实验结果表明了VDDTW算法用于在线签名认证的有效性。     

Writer-independent off-line signature verification using surroundedness feature

The paper presents a novel set of features based on surroundedness property of a signature (image in binary form) for off-line signature verification. The proposed feature set describes the shape of a signature in terms of spatial distribution of black pixels around a candidate pixel (on the signature). It also provides a measure of texture through the correlation among signature pixels in the neighborhood of that candidate pixel. So the proposed feature set is unique in the sense that it contains both shape and texture property unlike most of the earlier proposed features for off-line signature verification. Since the features are proposed based on intuitive idea of the problem, evaluation of features by various feature selection techniques has also been sought to get a compact set of features. To examine the efficacy of the proposed features, two popular classifiers namely, multilayer perceptron and support vector machine are implemented and tested on two publicly available database namely, GPDS300 corpus and CEDAR signature database.     

An approach for on-line signature authentication using Zernike moments

In this work, shape analysis of the acceleration plot, using lower order Zernike moments is performed for authentication of on-line signature. The on-line signature uses time functions of the signing process. The lower order Zernike moments represent the global shape of a pattern. The derived feature, acceleration vector is computed for the sample signature which comprises on-line pixels. The Zernike moment represent the shape of the acceleration plot. The summation value of a Zernike moment for a signature sample is obtained on normalized acceleration values. This type of substantiation decreases the influence of primary features with respect to translation, scaling and rotation at preprocessing stage. Zernike moments provide rotation invariance. In this investigation it was evident that the summation of magnitude of a Zernike moment for a genuine sample was less as compared to the summation of magnitude of a imposter sample. The number of derivatives of acceleration feature depends on the structural complexity of the signature sample. The computation of best order by polynomial fitting and reference template of a subject is discussed. The higher order derivatives of acceleration feature are considered. Signatures with higher order polynomial fitting and complex structure require higher order derivatives of acceleration. Each derivative better represents a portion of signature. The best result obtained is 4% of False Rejection Rate [FRR] and 2% of False Acceptance Rate [FAR].     

Relational consistency in on-line signature validation

An input signature is validated by elastic matching with a reference specimen signature. The matching algorithm is based on checking relational consistency only to an extent that is practicable in a low-cost real-time system.     

基于遗传算法的离线签名鉴定

提出一种基于遗传算法的离线签名鉴定方法。将签名图像分成多个子区域,提取各区域的分形维数矢量来描述笔迹的抖动程度,在此基础上,以形状特征、伪动态特征、分形维数作为签名的特征;运用加权欧式距离法构建分类器,并运用遗传算法对不同人的签名样本进行最优阈值选择。实验结果表明该方法能够取得较高的鉴别率。     

基于改进MFD距离的快速模板匹配新算法

针对最小远离距离MFD（Minimum Far Distance）算法对局部尖锐噪声易产生误匹配的问题,提出了一种改进的算法。新算法通过加入噪声阈值,对应点的灰度差值的相似阈值和单调递减累加阈值的方式,有效地去除了图像中的尖锐噪声,快速终止了非匹配点的计算,从而减少了总体的计算量。同时新算法采用了一种包含像素点差值的相关方法来解决同时出现多个匹配点的情况,从而显著抑制了模板的漂移问题。实验结果表明,算法在图像存在噪声、遮挡时都取得了比较满意的匹配效果。     

A new spontaneous pupillary oscillation-based verification system

A novel pupillary-based verification system is introduced, along with the early identity authentication results and analysis, based on the spatio-temporal features computed from the spontaneous pupillary oscillations. The authors demonstrate that this biometric trait has the capability to provide enough discriminative information to authenticate the identity of a subject. A new methodology to compute the spatio-temporal biometric template recordings of the pupil area changes, in a video-oculography sequence under constant luminance level, is also introduced in this paper. According to the authors’ knowledge, there is no evidence that other attempts were made, addressing this methodology to distinguish individuals based on the spatio-temporal representations, computed from the normal dilation-contraction behavior of the pupil. In this work, liveness will be detected by using the information obtained from the spontaneous pupillary oscillation mechanism. Preliminary experiments were conducted by using a particular own collected database, resulting in a (Equal Error Rate) in the order of 0.2338%.     

Fast template matching algorithm for contour images based on its chain coded description applied for human face identification

A new matching algorithm for contour images described by chain coded expression is presented. In our face authentication system, the isodensity contours has been introduced to differentiate between the facial features. These isodensity contours can be transformed into chain codes. By using these coded isodensity contours, remarkable improvement in the processing performance can be expected in terms of the processing time and memory requirements.From the computer simulation performed using images of 50 people, it turned out clear that the processing time was decreased to approximately one-seventh compared to the conventional method. With respect to memory requirement, it was reduced to a quarter.     

基于串匹配的源码抄袭检测技术研究

研究了基于字符串比较的代码抄袭检测技术,探讨了程序代码复制检测技术中代码预处理、标记串的生成及字符串比较等个关键问题.