A example of template The simplest one can be represented as t(i,j); 0<i<M, 0<j<N; (M and N are constant) 0<t(i,j)<256

A example of matching For (i=0;i<M;i++) For (j=0;j<N;j++) { If (a(i,j)==b(i,j)) S ab ++; }

True Acceptance Rate A genuine individual is accepted. (TAR) Threshold=0 means that the attempts whose matching score >0 will be accepted; (everybody will be accepted) Threshold=∞ means that the attempts whose matching score > ∞ will be accepted (nobody will be accepted)

False Rejection Rate A genuine individual is rejected. (FRR) Threshold=0 means that the attempts whose matching score <0 will be rejected; (nobody will be rejected) Threshold=∞ means that the attempts whose matching score < ∞ will be rejected (everybody will be rejected)

True Rejection Rate A impostor is rejected. (TRR) Threshold=0 means that the attempts whose matching score <0 will be rejected; (nobody will be rejected) Threshold=∞ means that the attempts whose matching score < ∞ will be rejected (everybody will be rejected)

False Acceptance Rate A impostor is accepted. (FAR) Threshold=0 means that the attempts whose matching score >0 will be accepted; (everybody will be accepted) Threshold=∞ means that the attempts whose matching score > ∞ will be accepted (nobody will be accepted)

ROC There are some trade off among TAR, FRR, TRR, FAR. We need a particular threshold to keep the TAR and TRR as high as possible and to keep FAR and FRR as low as possible. We need the ROC curve to find the optimal threshold. We also use ROC curve to evaluate the system

ROC(2) Find the optimal point (threshold)

ROC(3) Evaluate the system

Tut 1 Question 4

Tut 1 Question 5