Challenge Response Mechanism

In biometric authentication, challenge-response mechanisms confirm that the user is a live person and not an attempted spoof or replay attack. It presents randomized challenges (e.g., displaying specific instructions or prompts) to the user during the biometric capture process, ensuring a live and responsive interaction.

There are two main approaches:

1. Active Challenge-Response

Active solutions require the user to perform some kind of prompted action or response during the authentication process. Common examples include:

• Single-action responses like blinking, smiling, or nodding when prompted
• Variable-action responses, where the user is asked to perform a different randomized action each time, like turning their head in varying and unique directions.

Active challenge responses have limitations. Single-action prompts are predictable and vulnerable to scalable injection attacks using threats such as deepfakes or face swaps. However, active challenge response processes give fraudsters the key to reverse engineer attacks against the system. Face swaps could be used to meet the active challenge-response requirements in real time, too. Ultimately, an active challenge response is not an effective deterrent for fraudsters.

At the same time, active challenge-response mechanisms (by nature) create barriers for individuals with disabilities, as the required actions may be difficult or impossible for some users to complete. Impairing inclusivity and accessibility for those unable to perform challenge responses reliably can reduce its addressable market and damage organizational reputation. 

2. Passive Challenge-Response

The alternative is a passive approach, where the challenge-response process happens without requiring explicit user actions.

iProov advocates for passive, multi-frame biometric liveness processes that incorporate an unpredictable challenge-response sequence. Passive biometrics can ensure a high level of assurance without impeding inclusivity and accessibility. They provide the highest assurance that the user is not only ‘live’ but also authenticating in real-time – which is essential for defense against many sophisticated attack vectors.

Passive challenge-response mechanisms are randomized, making the authentication process unpredictable, impervious to replay attacks, and highly challenging to reverse-engineer. They also shift the complexity of the verification process to the background of the technology itself, minimizing user interaction and reducing barriers for individuals with disabilities.

How does iProov’s unique challenge-response mechanism work?

iProov’s patented Flashmark technology uses a structured sequence of coded illuminations from the user’s device as a passive challenge-response factor (alongside other core liveness detection capabilities). Flashmark illuminates a sequence of colors from the device screen onto the user’s face for a few seconds. The facial imagery with the sequence of colors is streamed back to iProov through the cloud, where it is determined if the color sequence is as expected. This confirms real-time authenticity.

While other liveness technologies require effort from the user, Flashmark enables users to authenticate by only looking at their device. It’s passive, inclusive, and highly secure.

By combining robust multi-frame liveness with a truly randomized passive challenge-response factor, you can achieve one of the highest levels of biometric assurance available without sacrificing user experience or inclusivity – a key advantage over traditional active challenge-response approaches.