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FMR / FAR / FRR settings

    Introduction

     

    In the world of biometrics, there are a few terms, which allow users to determin the effectiveness of fingerprint matching.  Some of them will be dealth with in this post. Three particular settings, namely FMR (False Match Rate), FAR (False Acceptance Rate) & FRR (False Rejection Rate) will assit in configuriing the reader for optimal effectiveness when implemented in various industries & onsite element exposures. Understanding the mechanisms of each will assist in analysing & applying the correct setting for optimum results. Each of these have a unique relationshipe with the other.

    Available from frimware versions 2.07c & 3.01d

     

    CONTENT

     

    FP relationship.png

    Definitions

     

    • FAR - The false acceptance rate is the measure of the likelyhood that the biometri reader will incorrectly accept an access attempt by an authorized user.
    • FRR - The false rejection rate is the measure of the likelyhood that the biometric reader will incorreclty reject an access attempt by an authorized user.
    • FMR - The false rejection rate is the measure of the likelyhood that the biometric reader will incorrectly match the authorized user to another authorized user's details.

    Symptoms

     

    In some cases a client may experience issues where an employee struggles to clock. Disecting the symptom will steer one towards applying the right setting. 

    • When a user is NOT enrolled & the device still accepts a presentation of his finger, the FAR persentage is too high & needs to be lowered.
    • When a user IS enrolled & the device denies him access by not accepting the presentation of his finger, the FRR persentage is too high & needs to be lowered.
    • When a user IS enrolled & the device accepts the presentation of his finger BUT, it shows a different employee's details, the FMR persentage is too high & needs to be lowered.

    Settings - FMR

    Set the minfpqf1 and/or minfpqf2 field in the daughter table to a value between 0 and 100. What this does is to reject the clocking if the reader determines the quality of the presented finger to be less than that specified.

     

    Example:

    minfpqf1 = 40 (All clockings with quality lower than 40% will not be validated & the employee would have to try again).

     

    Important:

    Setting this higher will result in the likelihood for ghost clockings to diminish but certainly will cause the individual to struggle if set too high. Our recommendation is to set this to 40%.

     

    Check out the screen dumps below. In Fig: 1 the setting has not been applied whereas in Fig: 2, it has. Immediately one notices that poor quality clockings are not considered “good enough” & forces the employee to try again until he gets a good score => 40%.

     

    Fig: 1

    Before.jpg

     

    Fig: 2

    After.jpg

     

    Statements to use when changing the setting using CMU:

     

    • select minfpqf1 from daughter;
    • update daughter set minfpqf1=40;
    • select minfpqf1 from daughter;

     

    Do the same for reader 2 if one has been connected.

    Don’t forget to reboot the clock!

     

    Settings - FAR & FRR

     

    Are two templates similar enough to call them a match. Most commonly configured, in aid of adapting to its exposure are the settings mentioned below & can be defined as detailed:

     

    1.       Security level - The lower the security level, the lower the percentage match that the reader will allow as a match.

    2.       Threshold level – Balancing the reader’s False Acceptance Rate (FAR) & False Rejection Rate (FRR).

     

    Performance setting 1 is easily set via CS Time or the clock’s onboard web interface. Performance setting 2 is done via the backend using our util CMU. This is because it is site dependent & only requires tweaking when the environment demands it.

     

    For sites with false acceptance issues, upping the threshold such that the FAR is reduced, at the expense of the FRR increasing, should solve the problem. Understanding this requires defining the FAR & FRR thresholds.

     

    In a practical scenario a low FAR & a high FRR would ensure that any unauthorized person will not be allowed access. It would also mean that the authorized people might have to put their finger on the device several times before they are allowed access. Therefore, it is good to have a very low FAR, but please remember that this low FAR is coming at the cost of high FAR. There is a distinct trade off between these two thresholds.

     

     In order to find a happy medium for each site one would have to tweak these values to such a degree where the employees are comfortably clocking but also that the integrity of the system is maintained.

     

    These values are stored in the clock’s database, in the daughter table as fpthreshold1 and fpthreshold2, one per FPR. The default the value is 22645, which gives both a false reject rate (FRR) and false accept rate (FAR) of under 1%. This default value was carefully chosen to meet the needs of most environments.

     

    Below then are the various values, which in turn will affect the readers FAR / FRR setting.


    FAR                  FRR                  Threshold

     

    0.01%               2.5%                 29990

    0.05%               1.8%                 27520

    0.1%                 1.4%                 26350

    0.5%                 1.0%                 23540

    0.82%               0.8%                 22645   -           Default

     

    Statements to use when changing the setting using CMU:

     

    • select fpthreshold1 from daughter;
    • update daughter set fpthreshold1=23540;
    • select fpthreshold1 from daughter;

     

    Do the same for reader 2 if one has been connected.

    Don’t forget to reboot the clock!

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    Page last modified 09:16, 7 Dec 2016 by Duaine CS TimeClock Documents > Hardware > FMR / FAR / FRR settings

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