With the widespread deployment of biometric authentication in Internet of Things (IoT) applications, protecting biometric templates while maintaining recognition performance and low resource consumption has become an important issue. However, existing revocable biometric template protection methods are mainly based on random projection, whose linear structure poses a reversibility risk when both transformation parameters and multiple protected templates are compromised. To address this issue, this paper proposes a revocable biometric template generation method, termed Weighted Absolute Value Transformation based on Random Bezier Matrices (WAVTRBM). The proposed method employs random Bezier matrices to preserve the discriminative information of biometric features during transformation, and introduces a random weight vector into the absolute value transformation to improve similarity preservation and matching performance. The method can generate both real-valued and binary protected templates, with the advantages of low storage overhead and fast computation, making it suitable for resource-constrained IoT devices and real-time authentication scenarios. Experiments on face, fingerprint, palmprint, and palm vein databases show that, compared with conventional random projection-based methods and existing absolute value transformation-based methods, the proposed method improves template security while maintaining good recognition performance and supporting efficient template generation and matching. Theoretical and experimental analyses further demonstrate that the proposed method satisfies the requirements of revocable biometrics and can resist various attacks.

With the rapid development of Internet of Things (IoT), biometric-based authentication systems have been widely used for access control. The wide application of biometric recognition systems has brought convenience but also raised privacy and security concerns. When unprotected templates are stolen, it will permanently leak the original biometric data. Therefore, it is important to ensure the security of biometric templates while meeting the real-time device requirements. Motivated by these issues, in this paper, we proposed a scheme based on partial Cake-cutting transformation and spherical hashing to generate cancelable binary face templates. Firstly, with external random parameters, partial Cake-cutting transformation is established to introduce randomness and preserve the relative distance similarity of face features. Then spherical hashing is utilized to encode the face features into protected binary codes. The protected template has the advantages of high entropy value, low storage consumption, and fast generation speed. Extensive experiments conducted on LFW, CFPW, and CASIA-FaceV5 databases along with theoretical analyses indicate that the proposed scheme shows good matching accuracy and strong resistance to various attacks. Besides, the protected templates can achieve equal or even better accuracy than the unprotected counterparts. Furthermore, the proposed scheme also satisfies the requirements of cancelable biometrics, i.e., irreversibility, revocability, and unlinkability.

Existing partial fingerprint matching methods use fingerprint ridge features and minutiae or employ algorithms like SIFT and A-KAZA to create new feature points that can replace minutiae for feature extraction and matching. While these methods have achieved some success in improving matching performance, they rely on manually designed rules for extracting local area features, which limits their accuracy and generalization capability. To address these limitations, this paper proposes a novel partial fingerprint matching algorithm that leverages Feature Similarity and Pre-training. Specifically, Feature Similarity is integrated into a deep learning-based model to emulate traditional partial fingerprint matching techniques. Additionally, Pre-training guides the model to learn subtle yet identity-discriminative features within partial fingerprints. Experimental results on partial fingerprint databases constructed from FVC2004 DB1, DB2, and DB3 show that our algorithm achieves low EER and ZeroFMR, outperforming several state-of-the-art matching methods.

With the widespread application of biometric, unprotected biometric data is still at risk of serious security and privacy breaches. When large amounts of unprotected biometric data leak, cancelable biometric become a powerfully remedial measure. In this paper, we propose a new method to generate stable and cancelable face templates based on multiple partial Walsh transformations (MPWT) and Simhash. Firstly, multiple partial Walsh matrices generated with random external parameters perform projection transformation on the original real-valued face features, ensuring the irreversibility and unlinkability of the system. Subsequently, the projected features are transformed into discrete binary codes (protected templates) using Simhash. And the random permutation seed ensures the revocability of generated protected template. Furtherly, the protected templates have small storage space and is more suitable for fast comparison but also yields improvements in recognition accuracy compared with several state-of-the-arts. Numerous experiments on CASIA-WebFace, LFW, FEI, and Color FERET databases show that the protected templates are nearly identical to the unprotected ones in the comparison performance. The scheme also meets the requirements of non-invertibility, revocability, unlinkability, as well as resistance for various types of attacks like attacks via record multiplicity, false accepts, brute force and pre-image. Therefore, the proposed methodology strikes a balance between recognition accuracy and security.

Cancelable biometrics is a powerful remedy for information leakage caused by the extensive usage of unprotected biometric data. Current measures usually suffer from deteriorated accuracy, which is known as the security–performance tradeoff. Motivated by these concerns, in this article, a novel cancelable fingerprint approach, i.e., Indexing-Min–Max (IMM) hashing, is proposed to securely transform a fixed-length fingerprint feature vector to a discrete index hashed code. IMM hashing is essentially established upon the min–max hash and further strengthened by the integration of the partial Hadamard transform, which alleviates performance deterioration while maintaining a high security level. Extensive experiments on FVC2002 and FVC2004 fingerprint datasets coupled with comprehensive theoretical analyses demonstrate the favorable accuracy and strong anti-attack resilience of the proposed method. Besides, compared to the unprotected counterpart, the matching precision of the protected templates yields little accuracy loss or even improved performance, which means the security–performance tradeoff is well handled. Furthermore, IMM hashing also meets the unlinkability and revocability requisites of cancelable biometrics.

Representing fingerprint templates in binary form can provide outstanding merits compared to the conventional minutiae-based fingerprint recognition system. The existing fixed-length fingerprint feature extraction methods either suffer from redundant feature magnitude or lack of template security. In this letter, we present a compact (128 bytes) and cancelable fingerprint binary codes generation scheme which enables accurate and efficient comparison as well as high security. This binary representation is also available for advanced encryption schemes (e.g., fuzzy commitment). Specifically, a kernel learning-based real-valued fingerprint feature is converted into compact and cancelable binary code via one permutation hashing. A partial Haar transform is deployed to further strengthen the irreversibility of the whole system. Experimental results on six benchmark datasets FVC2002 and FVC2004 coupled with security analysis demonstrate the superiority of the proposed method compared with several state-of-the-arts.

The minutiae set defined by the ISO/IEC 19794‐2 is one of the prevalent feature used in fingerprint recognition systems. Unfortunately, such characteristic of unordered and variable‐sized minutiae information causes a restriction on the operation in some advanced template protection methods (e.g. fuzzy commitment), which usually require an ordered and fixed‐length binary feature representation as the system input. In this study, in order to simultaneously extend the application of fingerprint recognition and provide satisfactory system performance, the authors propose a novel fixed‐length bit‐string conversion framework based on spectral clustering and the proposed newly designed discriminative fingerprint representation called minutia vicinity combined feature (MVCF). The proposed method consists of three stages: (i) the extraction of MVCF, (ii) bit conversion via the spectral clustering algorithm, and (iii) matching. Benefiting from feature invariance, fixed‐length and bit‐oriented coding, merits such as fast matching and decent accuracy are well guaranteed. The performance evaluation is conducted on six publicly available benchmark data sets: FVC2002 DB1, DB2, DB3 and FVC2004 DB1, DB2, DB3 confirms the superiority of the proposed method and suggests the promise of migrating to some other domains (e.g., template protection).

Small‐sized fingerprint sensors, due to the convenience of integration, are widely used in many applications, especially on smart phones. However, the friction ridge information decreases with the reduction of the collected fingerprint area, resulting in degraded recognition performance. Mosaicking fingerprint impressions has been proved to be effective in boosting the recognition accuracy. Nonetheless, the minutiae‐based mosaicking methods do not work well when there is no sufficient number of minutiae in the overlapping area while existing minutia‐free mosaicking methods are not robust to distortion and result in low mosaicking accuracy. In this study, a novel minutia‐free mosaicking algorithm used the coarse‐to‐fine approach is proposed to obtain a larger fingerprint impression from a couple of small‐sized fingerprint impressions. It consists of three stages: an orientation field‐based coarse alignment, a ridge matching‐based fine alignment, and a nonlinear deformation correction with block‐correspondence Thin Plate Spline model. Experimental results on the XDfinger database demonstrate that the proposed method outperforms the other six mosaicking methods in terms of reject‐to‐fuse rate, registration accuracy, and verification performance. Specifically, in the verification scenario, the equal error rate is reduced from 1.98% of a single impression to 0.41% of two impressions mosaicked by the authors' method.

In recent years, palmprint recognition has made great progress and many methods have been put forward. The extraction of robust orientation features and finding efficient matching strategies are two key points for palmprint recognition. Traditional coding methods usually only use a dominant filter response to extract orientation features of palmprint images while not taking into account the other useful filter responses. Without increasing the number of filers, this study presents a modified Competitive Code to extract orientation features more accurately, which makes use of the relation between the filter responses. Besides, a distinctive extended eight‐pixel neighbourhood method is proposed to select the sample points for matching by extracting the local features. At the matching stage, an effective fusion matching scheme with a double‐layer image pyramid is designed to calculate the similarity between two palmprint images. Extensive experiments on four types of public palmprint databases show that the proposed method has excellent performance compared with the other state‐of‐the‐art algorithms.

Local energy pattern, a statistical histogram-based representation, is proposed for texture classification. First, we use normalized local-oriented energies to generate local feature vectors, which describe the local structures distinctively and are less sensitive to imaging conditions. Then, each local feature vector is quantized by self-adaptive quantization thresholds determined in the learning stage using histogram specification, and the quantized local feature vector is transformed to a number by N-nary coding, which helps to preserve more structure information during vector quantization. Finally, the frequency histogram is used as the representation feature. The performance is benchmarked by material categorization on KTH-TIPS and KTH-TIPS2-a databases. Our method is compared with typical statistical approaches, such as basic image features, local binary pattern (LBP), local ternary pattern, completed LBP, Weber local descriptor, and VZ algorithms (VZ-MR8 and VZ-Joint). The results show that our method is superior to other methods on the KTH-TIPS2-a database, and achieving competitive performance on the KTH-TIPS database. Furthermore, we extend the representation from static image to dynamic texture, and achieve favorable recognition results on the University of California at Los Angeles (UCLA) dynamic texture database.

The naturally occurring aurora phenomenon is a dynamically evolving process. Taking temporal information into consideration, the auroral image sequence analysis is more reasonable and desirable than using static images only. However, the enormous richness of space structures and temporal variations make automatic auroral sequence analysis a particularly challenging task. In this paper, a hidden Markov model (HMM) based representation method including features of spatial texture and dynamic evolution is presented to characterize auroral image sequences captured by all-sky imagers (ASIs). The uniform local binary patterns are employed to describe the 2-D space structures of ASI images. HMM is feasible to characterize the doubly stochastic process involved in the auroral evolution-measurable polar light activities and hidden dynamic plasma processes. We present an affine log-likelihood normalization technique to manage the sequences with different lengths. The proposed method is used in the automatic recognition of four primary categories of ASI auroral observations between the years 2003 and 2009 at the Yellow River Station, Ny-Ålesund, Svalbard. The supervised classification results on manually labeled data in 2003 demonstrate the effectiveness of the proposed technique. Compared with frame-based classification, the higher accuracies and the lower rejection rates show the advantages of the sequence-based method. The occurrence distributions of the four aurora categories were obtained through automatic classification of data gathered from 2004 to 2009. Their agreement with the multiple-wavelength intensity distribution of the dayside aurora and the conclusions made from the frame-based method further illustrate the validity of our method on auroral representation and classification.

Information fusion offers a promising solution to the development of a high-performance classification system. In this paper, the problem of multiple gait features fusion is explored with the framework of the factorial hidden Markov model (FHMM). The FHMM has a multiple-layer structure and provides an alternative to combine several gait features without concatenating them into a single augmented feature. Besides, the feature concatenation is used to directly concatenate the features and the parallel HMM (PHMM) is introduced as a decision-level fusion scheme, which employs traditional fusion rules to combine the recognition results at decision level. To evaluate the recognition performances, McNemar's test is employed to compare the FHMM feature-level fusion scheme with the feature concatenation and the PHMM decision-level fusion scheme. Statistical numerical experiments are carried out on the Carnegie Mellon University motion of body and the Institute of Automation of the Chinese Academy of Sciences gait databases. The experimental results demonstrate that the FHMM feature-level fusion scheme and the PHMM decision-level fusion scheme outperform feature concatenation. The FHMM feature-level fusion scheme tends to perform better than the PHMM decision-level fusion scheme when only a few gait cycles are available for recognition.