問69
頻出度★★★
バイオメトリクス認証の他人受入率と本人拒否率に関する次の記述中の a，b に入れる字句の適切な組合せはどれか。 バイオメトリクス認証の認証精度において，他人受入率を低く抑えようとすると a が高くなり，本人拒否率を低く抑えようとすると b が高くなる。
令和7年度 ITパスポート試験 問69
This question's explanation and your answers so far.
解説
問 69
Incorrectア
a = security is correct, but b = availability is wrong. Keeping the false rejection rate low lets legitimate users pass authentication smoothly without being rejected. This is an improvement in ease of use, i.e., "convenience", not "availability", which refers to the degree to which the system stays up and usable.
- イ
正解 In biometric authentication, the "false acceptance rate (FAR)" and the "false rejection rate (FRR)" are in a trade-off relationship: when the decision threshold is adjusted, lowering one raises the other. Trying to keep the false acceptance rate low means tightening the decision to reject impostors, which reduces improper acceptances and raises "security" (a). On the other hand, trying to keep the false rejection rate low means loosening the decision so that the genuine user passes smoothly, making it easier for legitimate users to be authenticated and raising "convenience" (b). Therefore the combination a = security, b = convenience is correct, and the answer is イ.
Incorrectウ
a and b are swapped. Keeping the false acceptance rate low (making it harder for impostors to pass) improves "security", not "convenience", while keeping the false rejection rate low (making it easier for the genuine user to pass) improves "convenience", not "security". Because the combination is reversed, it is wrong.
Incorrectエ
a = convenience is wrong (keeping the false acceptance rate low improves security), and b = availability is also wrong (keeping the false rejection rate low improves convenience). Neither holds.
ここがポイント
- The false acceptance rate (FAR) and the false rejection rate (FRR) are in a trade-off relationship. Lowering one raises the other, so the decision threshold is adjusted according to the use case.
- Lowering FAR = making it harder for impostors to pass → security improves. Lowering FRR = making it easier for the genuine user to pass → convenience improves.
用語