Passive Liveness Detection
The passive liveness detection is a process of determining whether the face presented on a photo is a real person, without requiring the user to perform any additional challenge (unlike active liveness detection).
This liveness detection method is recommended for applications where the user’s experience and seamless app flow is paramount.
DOT passive liveness detection achieved iBeta Level 2 PAD accreditation in accordance with ISO 30107-03 PAD. See the confirmation letter. More on the test specification.
Technical documentation
Details on using the liveness detection in Digital Identity Service can be found in the technical documentation in the Liveness functionality.
Photo Capture Method for Passive Liveness Detection
It is important that in the onboarding process the user cannot upload a photo him/herself. It has to be strictly enforced that the user has to take the selfie at the time of enrollment. It is strongly recommended to use the Innovatrics' face auto capture component, whether mobile or web one. Being able to upload a selfie photo allows the user to generate synthetic faces or do image manipulation that cannot be detected. Enforcing the usage of camera allows the liveness check to detect screen attack and injection is detected with the Video Injection Prevention.
Passive Liveness Image Requirements
The first step of performing the passive liveness detection is face detection in the image. It is important for the image to fullfill quality requirements in order to detect the face and to determine the liveness. Requirements for the image are:
- image size at least 600x600 pixels
- distance between the eyes at least 120 pixels
- shorter side of the image should be at least 4 times the distance between the eyes in pixels
- face should be near the center of the image
- not too strong backlight or sidelight
- no overexposed or underexposed images
- ICAO attributes are recommended to be compliant with the table at the bottom
- JPEG capture quality should be at least 80%
- image should not be cropped or manipulated between the capture and the processing step
Presentation Attack Detection Types
Our algorithm has been trained to detect real faces and also various kinds of spoof attacks. These include:
- Screen attacks - faces presented to camera on a screen
- Printed faces on a paper presented to camera
- 2D masks - faces printed on a cardboard with cutouts and worn by a person’s face
- 3D masks - silicone masks, dolls and manequins
(Synthetic face images and photo manipulation can be detected with Video Injection Detection)
We recognize that new attacks might emerge, so we regularly retrain the models to incorporate new attack vectors. It is also important that our customers keep the installed components up to date as we are releasing them.
Evaluating Passive Liveness Scores - Setting a Correct Threshold
The result of the passive liveness algorithm is a score. This is a value in the range 0 to 1. (Not to be mistaken with probability percentage, the behaviour here is nonlinear.)
The result whether a face photo is genuine or fraud attempt is decided by comparison of the passive liveness score and the threshold. If the score is above the threshold, it is classified as genuine and thus accepted. If the score is below the threshold, it is classified as a fraud and thus rejected.
Passive Liveness Scores, Error Rates and Accuracy
- FAR: Fraud attempt images that are classified as genuine are false accepts. The percentual rate of such error on a given dataset and given threshold represents the False Accept Rate (FAR).
- FRR: Genuine images that are classified as frauds are false rejects. The percentual rate of such error on a given dataset and given threshold represents the False Accept Rate (FAR).
- EER: Threshold at which are the FAR and FRR equal is called Equal Error Rate. This can be considered as the accuracy metric of the algorithm for given dataset.
Example:
Imagine a dataset of 10,000 genuine photos of real faces and 1,000 fraudulent photos, where measurements were made. Threshold of 0.895, which is at working point of 1% FAR results in 8.1% FRR. That means there are 10 fraudulent photos marked as genuine (false accepts) and 810 genuine photos are marked as frauds (false rejects).
Datasets and Extrapolating Measurements to Real World Usage
The measured results and accuracy of the liveness detection depend on the dataset used to calculate them. If such dataset is large and representative for required use case, the measurement results can be extrapolated for real world conditions.
However, the real world conditions and thus the accuracy of the algorithm differ from project to project. The behaviour and accuracy of liveness algorithm may be affected by the demographics of the user population, prevailing daylight conditions when it is used, quality of the phones used by the population and configuration of the autocapture components in the client app.
The Innovatrics' 2023 validation dataset consists of 125,000 photos with genuines and frauds represented equally. Unlike the dataset used previously, this one has sophisticated fraud attempts in order to better quantify the security precision.
Recommendations for Passive Liveness Deployment in Projects
It is recommended for the pilot phase of the project to set the threshold according to our measurements below. If there is available helpdesk personel and implementation allows it, there could be 2 thresholds set, one for automatic rejection and one for automatic acceptance. The photos between these two thresholds are to be evaluated by personel. Having processed thousands of photos, an accuracy measurement should be made on the collected dataset to adjust the used thresholds.
For onboarding and login use cases, the passive liveness detection has to be always combined with face matching. This ensures not only that the presented face is real, but it checks also whether it belongs to the person expected.
Thresholds for Passive Liveness
The tables below provide measured threshold for defined performance on the new Innovatrics' 2023 dataset.
Digital Identity Service 1.29 and above (new 2023 dataset)
The table below shows the thresholds for new UNIVERSAL liveness model, which is default since version 1.29. It is possible to revert to the older STANDARD model, which is the same as in v1.28. See the table for v1.28 for configuration.
| Use case type | Threshold | Performance |
|---|---|---|
| Convenience (minimum rejected attempts) | 0.805 | 2.3% FAR @ 1% FRR |
| Balanced (equal error rate) | 0.85 | 1.3% both FAR & FRR |
| Security (minimum accepted frauds) | 0.895 | 4.1% FRR @ 1% FAR |
Speed Comparison of the Models
The new UNIVERSAL model is slower compared to the STANDARD as a tradeoff for the higher accuracy. On a reference AWS machine c6a.large the STANDARD takes 180 ms, while the UN?IVERSAL takes 500 ms.
Digital Identity Service 1.22 till 1.28 (new 2023 dataset)
| Use case type | Threshold | Performance |
|---|---|---|
| Convenience (minimum rejected attempts) | 0.83 | 4.4% FAR @ 1% FRR |
| Balanced (equal error rate) | 0.87 | 1.8% both FAR & FRR |
| Security (minimum accepted frauds) | 0.905 | 5.1% FRR @ 1% FAR |
Digital Identity Service 1.10 till 1.19 (new 2023 dataset)
| Use case type | Threshold | Performance |
|---|---|---|
| Convenience (minimum rejected attempts) | 0.82 | 11% FAR @ 1% FRR |
| Balanced (equal error rate) | 0.885 | 3.8% both FAR & FRR |
| Security (minimum accepted frauds) | 0.93 | 13% FRR @ 1% FAR |
Passive liveness on Mobile Devices
For native mobile use cases where the liveness detection must be performed without the server connectivity fully offline - Mobile SDK libraries provide the lightweight version of passive liveness detection. Server-side liveness detection offers higher security and better user experience and should be used whenever possible. Passive liveness score can be obtained from the quality attributes returned by the Face Capture UI component.
Evaluating the ICAO Image Quality in Mobile Libraries
PassiveLivenessQualityProvider used in mobile auto capture components can ensure that all these conditions are met during the capture. These are the optimal values for liveness detection required in the quality provider:
| Attribute | Min | Max |
|---|---|---|
| BRIGHTNESS | 0.11 | 0.75 |
| CONTRAST | 0.25 | 0.8 |
| SHARPNESS | 0.3 | 1 |
| UNIQUE_INTENSITY_LEVELS | 0.525 | 1 |
| PITCH_ANGLE | -15 | 15 |
| YAW_ANGLE | -20 | 20 |
Passive liveness threshold - on client
The Passive liveness models on client (in DOT Face mobile libraries) are lightweight and therefore provide different FAR/FRR statistics. The Passive liveness detection on client is not recommended and should be used for features like face login, but not for authorization.
Thresholds for mobile libraries DOT Face (new 2023 dataset)
| Use case type | Threshold | Performance |
|---|---|---|
| Convenience (minimum rejected attempts) | 0.8 | 10% FAR @ 1% FRR |
| Balanced (equal error rate) | 0.88 | 3.2% both FAR & FRR |
| Security (minimum accepted frauds) | 0.93 | 11% FRR @ 1% FAR |