총평:
- Coursework에서 Paper critique 해서 읽었습니다 (지능형모바일시스템)
- 딥러닝과 관련 되어있지만, 새로운 학습적 novelty를 제안한 것은 아닙니다.
- 일반적인 지문인식을 통한 authentication이 아니라, 손가락과 휴대폰의 상호작용을 통해 발생하는 소리를 통해 사용자를 identify/authenticate하는 논문입니다. 신기한 내용이어서 재미있게 읽었습니다.
- 음성 전처리/후처리 부분은 잘 몰라서 제대로 읽지 못했습니다.
- best paper를 받을만한 innovation/실험 설정 / 실험 결과 라고 생각합니다.
Task: Biometric system for user identification
Contributions
- Hypothesizes that the FiSe(finger-induced sonic effect) from "finger" swiping on "phone" contains intrinsic fingerprint information
- Design SonicPrint: a biometric system applicable to smart devices using this FiSe
- Shows up to 97% accuracy on mobile phones, and resilience against fake-finger and replay attacks
- Note that since this method uses the 'sound' input, it does not require touch sensors - and is (in theory) applicable to all smart devices
Motivation: Adopting touch sensors in small smart devices in infeasible (hardware constraints)
Method outline
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Background isolation
- Pre-process sound input (high pass filter)
- Sonic effect enhancement using Multi-band spectral subtraction
- Denoising-aware wavelet reconstruction
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Friction event detection
- Adaptive detection via Hidden Markov Model (acoustic event detection)
- phase-based detection & duration verificatino for robustness
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Acoustic fingerprint analysis
- Identify fingerprint features (by level) -> then determine fingerprint-induced sonic features
- ex) Arch, Line-Unit, Pores are fingerprint features
- ex) Temporal centroid, Mel-frequency cepstral coefficients are fingerprint-induced sonic features
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Ensemble classification
- Uses ensemble of the following models for final identification:
- Logistic Regression
- SVM
- Random Forest
- Linear Discriminant Analysis
- Gaussian Mixture Model
- Uses ensemble of the following models for final identification:
Evaluation / Discussions
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based on data & reponses from 31 users
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Balanced accuracy around 80% ~ 90% based on the type of interaction (type of swipe)
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Reaches up to 97% when the surface is rough, and the sound is more distinguishable
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Successfully eliminates alien fingers (untrained fingers) at test time
- FP rate around 2%
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As the number of subjects increase, performance decreases
- But usually do not register a lot of subjects in one phone
- After 15 subjects, learns more accurate features for better identification! (performance bounces)
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more suitable for rough spaces vs smooth spaces
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The more curved the surface, lower performance
- since only partial fingerprint is in contact with the surface
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Performance is proportional to complexity of swipe pattern
- more complex -> longer length -> more user-specific information for identification
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Performance also depends on position of swipe w.r.t microphone position
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Resilient against fingerprint phantom attack (fake finger) and replay attack (record sound and replay)
- due to different surface characteristics & small sound
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May be vulnerable to inaudible ultrasound signals
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Not robust when trained only in controlled environment (with controlled noise)