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Chapter 5

Chapter 5. Basic System Errors (Alireza Tavakkoli). Outline. Matching The Receiver Operating Curves (ROC) Error Conditions Specific to Biometrics Negative Authentication Trade-offs. Matching. Definition Notations:. Biometric Uniqueness. Similarity measure  Prob (B=B’)

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Chapter 5

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  1. Chapter 5 Basic System Errors (Alireza Tavakkoli)

  2. Outline • Matching • The Receiver Operating Curves (ROC) • Error Conditions Specific to Biometrics • Negative Authentication • Trade-offs

  3. Matching • Definition • Notations: Biometric Uniqueness

  4. Similarity measure  Prob (B=B’) Higher match score  Higher Prob. Similarity  d(B’,B) [0,Inf.)  [0,1] Matching Scores

  5. The Tail of Two Errors • Hypothesis Test and Errors: • Two Errors: • False Match (Type I) • Flase Non-match (Type II)

  6. Score Distributions Hard Decision Reliability of s

  7. FMR and FNMR

  8. Estimating Error from Data • Access to G(y) & F(x) • Estimation: • Need to be studied more

  9. Error Rates of Match Engines • FM and FNM • Accept/Reject Object • FA and FR • Accept/Reject Null Hypothesis

  10. Positive Authentication • Errors in Pos. Authentication: • False Accept (FA) • False Reject (FR) • Problems: • FA  Security Breach • FR  Convenience Problems

  11. ROC - Design vs Application - Security vs Convenience FMR ↑ FNMR ↓

  12. Semi-log plots Log-log plot Variations of ROCs

  13. Using the ROC Curve • Comparing matchers • Tradeoff between FMR & FNMR. • Specific Threshold  FMR(T)/FNMR(T)

  14. Expressing Quality of ROC • The Equal Error Rate: • d-prime: • Expected Overall Error • Cost Function

  15. Expressing Quality of ROC • The Equal Error Rate:

  16. Expressing Quality of ROC • d-prime:

  17. Expressing Quality of ROC • Expected Overall Error

  18. Expressing Quality of ROC • Cost Function

  19. Error Conditions Specific to Biometrics • FTAFTEFTU Significant Cost. • FTA: • FTE: • Manual vs Automatic Authentication • CMC or RPM

  20. Negative Authentication • Negative Hypotheses: • The Two Errors: • Falsely missing B • Incorrectly matching B and B’.

  21. Negative Authentication • Detection Theory Terminology: • False Negative • False Positive

  22. Different Errors  Different Outcomes False Accept  Security Breach. False Reject  Inconvenience. Convenience vs Security Cost vs Security Cost of Negative Authentication Trade Offs

  23. Convenience vs Security • Convenience of a Biometric • Convenience of Implementation

  24. Cost vs Security in Pos. Auth. • Why it is important • FRR ↑ Service denial  Exception handling • Dynamic Authentication Protocol

  25. Cost of Negative Authentication • Screening: • Higher FPR&FNR  Inconvenient to all

  26. Neg. Vs Pos. Authentiocation

  27. Questions?

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