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

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 Variations of ROCs Semi-log plots Log-log plot

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

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?