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Department of Electrical EngineeringBiometrics such as fingerprint, iris, face, and electrocardiogram (ECG) have been investigated as convenient and powerful security tools that can potentially replace or supplement current possession or knowledge based authentication schemes. Recently, multi-spectral skin photomatrix (MSP) has been newly found as one of the biometrics. Moreover, since the interest of usage and security for wearable devices have been increasing, multi-modal biometrics authentication which is combining more than two modalities such as (iris + face) or (iris + fingerprint) for powerful and convenience authentication is widely proposed. However, one practical drawback of biometrics is irrevocability. Unlike password, biometrics can not be canceled and re-used once compromised since they are not changed forever. There have been several works on cancelable biometrics to overcome this drawback. ECG has been investigated as a promising biometrics, but there are few research on cancelable ECG biometrics. As we aim to study a way for multi-modal biometric scheme for wearable devices that is assumed circumstance under some limitations such as relatively high performance, low computing power, and limited information (not sharing users information to the public), in this study, we proposed a multi-modal biometrics authentication by combining ECG and MSP. For investigating the performances versus level of fusions, Adaboost algorithm was studied as a score level fusion method, and Majority Voting was studied as a decision level fusion method. Due to ECG signal is 1 dimensional, it provides benefits in wearable devices for overcoming the computing memory limitation. The reasons that we select MSP combination with ECG are it can be collected by measuring on inner-wrist of human body and it also can be considered as hardly stolen modality in remote ways. For proposed multi-modal biometrics, We evaluate our methods using collected data by Brain-Computer-Interface lab with 63 subjects. Our Adaboost based pro- posed multi modal biometrics method with performance boost yielded 99.7% detection probability at 0.1% false alarm ratio (PD0.1) and 0.3% equal error rate (EER), which are far better than simply combining by Majority Voting algorithm with 21.5% PD0.1 and 1.6% EER. Note that for training the Adaboost algorithm, we used only 9 people dataset which is assumed as public data and not included for testing data set, against for knowledge limitation as the other constraint. As initial step for user template protection, We proposed a cancelable ECG based user authentication using a composite hypothesis testing in compressive sensing do- main by deriving a generalized likelihood ratio test (GLRT) detector. We also pro- posed two performance boost tricks in compressive sensing domain to compensate for performance degradation due to cancelable schemes: user template guided filtering and T-wave shift model based GLRT detector for random projection domain. To verify our proposed method, we investigated cancelable biometrics criteria for the proposed methods to confirm that the proposed algorithms are indeed cancelable. For proposed cancelable ECG authentication, We evaluated our proposed methods using ECG data with 147 subjects from three public ECG data sets (ECG-ID, MIT- BIH Normal / Arrhythmia). Our proposed cancelable ECG authentication method is practically cancelable by satisfying all cancelable biometrics criteria. Moreover, our proposed method with performance boost tricks achieved 97.1% detection probability at 1% false alarm ratio (PD1) and 1.9% equal error rate (EER), which are even better than non-cancelable baseline with 94.4% PD1 and 3.1% EER for single pulse ECG authentication.ope

Cancelable ECG Biometrics using Compressive Sensing-Generalized Likelihood Ratio Test

Electrocardiogram (ECG) has been investigated as promising biometrics, but it cannot be canceled and re-used once compromised just like other biometrics. We propose methods to overcome the issue of irrevocability in ECG biometrics without compromising performance. Our proposed cancelable user authentication uses a generalized likelihood ratio test (GLRT) based on a composite hypothesis testing in compressive sensing (CS) domain We also propose a permutation-based revocation method for CS-based cancelable biometrics so that it becomes resilient to record multiplicity attack. In addition, to compensate for inevitable performance degradation due to cancelable schemes, we also propose two performance improvement methods without undermining cancelable schemes: a self-guided ECG filtering and a T-wave shift model in our CS-GLRT. Finally, our proposed methods were evaluated for various cancelable biometrics criteria with the public ECG-ID data (89 subjects). Our cancelable ECG biometric methods yielded up to 93.0% detection probability at 2.0% false alarm ratio (PD*) and 3.8% equal error rate (EER), which are comparable to or even better than non-cancelable baseline with 93.2% PD* and 4.8% EER for challenging single pulse ECG authentication, respectively. Our proposed methods met all cancelable biometrics criteria theoretically or empirically. Our cancelable secure user template with our novel revocation process is practically non-invertible and robust to record multiplicity attack

A Wearable Wrist Band-Type System for Multimodal Biometrics Integrated with Multispectral Skin Photomatrix and Electrocardiogram Sensors

Multimodal biometrics are promising for providing a strong security level for personal authentication, yet the implementation of a multimodal biometric system for practical usage need to meet such criteria that multimodal biometric signals should be easy to acquire but not easily compromised. We developed a wearable wrist band integrated with multispectral skin photomatrix (MSP) and electrocardiogram (ECG) sensors to improve the issues of collectability, performance and circumvention of multimodal biometric authentication. The band was designed to ensure collectability by sensing both MSP and ECG easily and to achieve high authentication performance with low computation, efficient memory usage, and relatively fast response. Acquisition of MSP and ECG using contact-based sensors could also prevent remote access to personal data. Personal authentication with multimodal biometrics using the integrated wearable wrist band was evaluated in 150 subjects and resulted in 0.2% equal error rate ( EER ) and 100% detection probability at 1% FAR (false acceptance rate) ( PD.1 ), which is comparable to other state-of-the-art multimodal biometrics. An additional investigation with a separate MSP sensor, which enhanced contact with the skin, along with ECG reached 0.1% EER and 100% PD.1 , showing a great potential of our in-house wearable band for practical applications. The results of this study demonstrate that our newly developed wearable wrist band may provide a reliable and easy-to-use multimodal biometric solution for personal authentication

Cancelable ECG Biometrics using GLRT and Performance Improvement using Guided Filter with Irreversible Guide Signal

Biometrics such as ECG provides a convenient and powerful security tool to verify or identify an individual. However, one important drawback of biometrics is that it is irrevocable. In other words, biometrics cannot be re-used practically once it is compromised. Cancelable biometrics has been investigated to overcome this drawback. In this paper, we propose a cancelable ECG biometrics by deriving a generalized likelihood ratio test (GLRT) detector from a composite hypothesis testing in randomly projected domain. Since it is common to observe performance degradation for cancelable biometrics, we also propose a guided filtering (GF) with irreversible guide signal that is a non-invertibly transformed signal of ECG authentication template. We evaluated our proposed method using ECG-ID database with 89 subjects. Conventional Euclidean detector with original ECG template yielded 93.9% PD1 (detection probability at 1% FAR) while Euclidean detector with 10% compressed ECG (1/10 of the original data size) yielded 90.8% PD1. Our proposed GLRT detector with 10% compressed ECG yielded 91.4%, which is better than Euclidean with the same compressed ECG. GF with our proposed irreversible ECG template further improved the performance of our GLRT with 10% compressed ECG up to 94.3%, which is higher than Euclidean detector with original ECG. Lastly, we showed that our proposed cancelable ECG biometrics practically met cancelable biometrics criteria such as efficiency, re-usability, diversity and non-invertibility