Biometrics 简明教程
Behavioral Modalities
行为生物识别技术涉及人员的行为或人员执行任务（如走路、签名和键盘输入）的方式。
Behavioral biometrics pertains to the behavior exhibited by people or the manner in which people perform tasks such as walking, signing, and typing on the keyboard.
行为生物识别方式具有更高的差异性，因为它们主要取决于疲劳、情绪等外部因素。与基于生理生物识别技术的解决方案相比，这会导致较高的 FAR 和 FRR。
Behavioral biometrics modalities have higher variations as they primarily depend on the external factors such as fatigue, mood, etc. This causes higher FAR and FRR as compared to solutions based on a physiological biometrics.
Gait Recognition
Gait 是一个人的行走方式。人们在行走时表现出不同的特征，例如身体姿势、行走时两英尺之间的距离、摇摆等，这些特征有助于识别他们。
Gait is the manner of a person’s walking. People show different traits while walking such as body posture, distance between two feet while walking, swaying, etc., which help to recognize them uniquely.
基于对候选人走路视频图像进行分析的步态识别。候选人行走周期的样本由视频记录。然后分析样本以确定膝盖和脚踝等关节的位置，以及在行走时它们之间的角度。
A gait recognition based on the analyzing the video images of candidate’s walk. The sample of candidate’s walk cycle is recorded by Video. The sample is then analyzed for position of joints such as knees and ankles, and the angles made between them while walking.
为每个人员创建一个相应的数学模型并将其存储在数据库中。在验证时，该模型与候选人步态的实时样本进行比较以确定其身份。
A respective mathematical model is created for every candidate person and stored in the database. At the time of verification, this model is compared with the live sample of the candidate walk to determine its identity.
Merits of Gait Recognition System
-
It is non-invasive.
-
It does not need the candidate’s cooperation as it can be used from a distance.
-
It can be used for determining medical disorders by spotting changes in walking pattern of a person in case of Parkinson’s disease.
Signature Recognition System
在这种情况下，签名方式的行为模式比图形形式的签名外观得到更多强调。
In this case, more emphasis is given on the behavioral patterns in which the signature is signed than the way a signature looks in terms of graphics.
行为模式包括书写时间、停顿、压力、笔画方向和签名过程中的速度的变化。复制签名的图形外观可能容易，但要模仿签名的行为模式却不容易。
The behavioral patterns include the changes in the timing of writing, pauses, pressure, direction of strokes, and speed during the course of signing. It could be easy to duplicate the graphical appearance of the signature but it is not easy to imitate the signature with the same behavior the person shows while signing.
此项技术包括一支笔和平板电脑，两者都连接到计算机，用于模板比较和验证。高品质平板电脑可以在签名时捕获速度、压力和时间等行为特征。
This technology consists of a pen and a specialized writing tablet, both connected to a computer for template comparison and verification. A high quality tablet can capture the behavioral traits such as speed, pressure, and timing while signing.
在注册阶段，候选人必须在绘图板上多次签字以获取数据。然后，签名识别算法提取唯一特征，如时间、压力、速度、笔画方向、签名路径上的重要点和签名大小。算法为这些点指定不同的权重值。
During enrollment phase, the candidate must sign on the writing tablet multiple times for data acquisition. The signature recognition algorithms then extracts the unique features such as timing, pressure, speed, direction of strokes, important points on the path of signature, and the size of signature. The algorithm assigns different values of weights to those points.
在识别时，候选人输入签名的实时样本，将其与数据库中的签名进行比较。
At the time of identification, the candidate enters the live sample of the signature, which is compared with the signatures in the database.
Constraints of Signature Recognition System
-
To acquire adequate amount of data, the signature should be small enough to fit on tablet and big enough to be able to deal with.
-
The quality of the writing tablet decides the robustness of signature recognition enrollment template.
-
The candidate must perform the verification processes in the same type of environment and conditions as they were at the time of enrollment. If there is a change, then the enrollment template and live sample template may differ from each other.
Merits of Signature Recognition System
-
Signature recognition process has a high resistance to imposters as it is very difficult to imitate the behavior patterns associated with the signature.
-
It works very well in high amount business transactions. For example, Signature recognition could be used to positively verify the business representatives involved in the transaction before any classified documents are opened and signed.
-
It is a non-invasive tool.
-
We all use our signature in some sort of commerce, and thus there are virtually no privacy rights issues involved.
-
Even if the system is hacked and the template is stolen, it is easy to restore the template.
Keystroke Recognition System
在二战期间，军事情报部门使用一种称为发送者拳头（Fist of the Sender）的技术，根据打字节奏来确定莫尔斯电码是由敌人还是盟军发送的。如今，就硬件而言，击键动力学是最容易实现的生物识别解决方案。
During the World War II, a technique known as Fist of the Sender was used by military intelligence to determine if the Morse code was sent by enemy or ally based on the rhythm of typing. These days, keystroke dynamics the easiest biometric solution to implement in terms of hardware.
此生物识别分析候选人的打字模式、节奏和在键盘上打字的速度。击键识别中使用 dwell time 和 flight time 测量。
This biometric analyzes candidate’s typing pattern, the rhythm, and the speed of typing on a keyboard. The dwell time and flight time measurements are used in keystroke recognition.
Dwell time −它是一个键被按下的持续时间。
Dwell time − It is the duration of time for which a key is pressed.
Flight time −它是在松开一个键和按下下一个键之间经过的时间。
Flight time − It is the time elapsed between releasing a key and pressing the following key.
候选人在键盘上的打字方式有所不同，因为他们找到正确按键所需的时间、飞行时间和停留时间有所不同。他们的打字速度和节奏也根据他们对键盘的熟练程度而异。击键识别系统在一次尝试中每秒监测键盘输入数千次，以根据他们的打字习惯识别用户。
The candidates differ in the way they type on the keyboard as the time they take to find the right key, the flight time, and the dwelling time. Their speed and rhythm of typing also varies according to their level of comfort with the keyboard. Keystroke recognition system monitors the keyboard inputs thousands of times per second in a single attempt to identify users based on their habits of typing.
击键识别有两种类型−
There are two types of keystroke recognition −
-
Static − It is one time recognition at the start of interaction.
-
Continuous − It is throughout the course of interaction.
Application of Keystroke Dynamics
-
Keystroke Recognition is used for identification/verification. It is used with user ID/password as a form of multifactor authentication.
-
It is used for surveillance. Some software solutions track keystroke behavior for each user account without end-user’s knowledge. This tracking is used to analyze if the account was being shared or used by anyone else than the genuine account owner. It is used to verify if some software license is being shared.
Merits of Keystroke Recognition System
-
It needs no special hardware to track this biometric.
-
It is a quick and secure way of identification.
-
A person typing does not have to worry about being watched.
-
Users need no training for enrollment or entering their live samples.
Demerits of Keystroke Recognition System
-
The candidate’s typing rhythm can change between a number of days or within a day itself because of tiredness, sickness, influence of medicines or alcohol, change of keyboard, etc.
-
There are no known features dedicated solely to carry out discriminating information.