Biometrics 简明教程

Biometric System Performance

生物特征识别系统制造商声称系统性能很高，而在实际操作环境中实际上很难实现这一点。可能的原因是，在受控的环境设置、硬件的限制等条件下进行的测试。

Biometric system manufacturers claim high system performance which is practically difficult to achieve in actual operating environments. The possible reasons are, tests conducted in controlled environment setups, limitations on hardware, etc.

例如，语音识别系统只能在安静的环境中有效工作，面部识别系统如果照明条件受到控制，并且受试者接受过适当清洗和放置手指的训练，则可以正常工作。

For example, a voice recognition system can work efficiently only in quiet environment, a facial recognition system can work fine if lighting conditions are controlled, and candidates can be trained to clean and place their fingers properly on the fingerprint scanners.

然而，在实践中，在目标操作环境中可能无法获得这样的理想条件。

However, in practice, such ideal conditions may not be available in the target operating environment.

Performance Measurements

生物特征识别系统的性能测量与拒绝错误率 (FRR) 和接受错误率 (FAR) 密切相关。

The performance measurements of a biometric system are closely tied to False Reject Rate (FRR) and False Accept Rate (FAR).

FRR 也称为 Type-I error 或假不匹配率 (FNMR)，它表示合法用户被系统拒绝的可能性。

FRR is also known as Type-I error or False Non Match Rate (FNMR) which states the likelihood of a legitimate user being rejected by the system.

FAR 被称为 Type-II error 或错误匹配率 (FMR)，它表明系统接受虚假身份声明的可能性。

FAR is referred to as Type-II error or False Match Rate (FMR) which states the likelihood of a false identity claim being accepted by the system.

理想的生物特征系统预计对 FAR 和 FRR 都产生零值。这意味着它应该接受所有真正用户并拒绝所有虚假身份声明，但这实际上是无法实现的。

An ideal biometric system is expected to produce zero value for both FAR and FRR. Means it should accept all genuine users and reject all fake identity claims, which is practically not achievable.

FAR 和 FRR 成反比。如果 FAR 得到改善，则 FRR 会下降。 high FRR ensures high security 的生物特征系统。如果 FRR 过高，则系统需要多次输入活体样本，这会降低效率。

FAR and FRR are inversely proportional to each other. If FAR is improved, then the FRR declines. A biometric system providing high FRR ensures high security. If the FRR is too high, then the system requires to enter the live sample a number of times, which makes it less efficient.

当前生物特征技术的性能远未达到理想状态。因此，系统开发人员需要根据安全要求在这两个因素之间保持良好的平衡。

The performance of current biometrics technologies is far from the ideal. Hence the system developers need to keep a good balance between these two factors depending on the security requirements.