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Commonly confused · Security Fundamentals & Crypto

FAR vs FRR vs CER: Biometric Error Rates Explained

FAR is how often a biometric system wrongly accepts an impostor (Type II error), FRR is how often it wrongly rejects a legitimate user (Type I error), and CER is the point where FAR and FRR are equal, used to compare overall accuracy.

False Acceptance Rate (FAR)

Full definition
vs

False Rejection Rate (FRR)

Full definition
vs

Crossover Error Rate (CER)

Full definition
False Acceptance RateFalse Rejection RateCrossover Error Rate
Also calledType II errorType I errorEqual Error Rate (EER)
What goes wrongImpostor gets inValid user is deniedNot an error, a comparison point
Main impactSecurity breachUser frustration, productivity lossAccuracy benchmark
Raising sensitivityDecreasesIncreasesUnchanged, it is a property of the system
Lower is better?YesYesYes, lower CER means more accurate device
Remember it

FAR lets the Fake in; FRR Rejects the Real; CER is where they Cross.

Exam tip

Know that a lower CER means a better biometric system. CISSP tests Type I versus Type II naming, so tie Type II to the more dangerous false acceptance.

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