The Complete Guide to Biometric Authentication and Zero-Knowledge Technology
12 May 2025
The Complete Guide to Biometric Authentication and Zero-Knowledge Technology
12 May 2025
The most fundamental part of any authentication technology is its ability to prove that someone is who they say they are.
As passwords continue with their slow decline, passwordless authentication has stepped in to take their place. Technologies like call center verification, SMS one-time password OTPs, passkeys, and biometrics all offer ways for users to verify their identity without relying on a password.
But not all passwordless technologies work the same way. The landscape is varied and not every approach provides the same level of security, privacy, or user experience.
In this guide, we’ll explore the key differences between these technologies and explain why biometrics are more often than not the technology of choice when it comes to answering the first and most important question: Is this person really who they say they are?
The Different Types of Passwordless Authentication Solutions
There are several types of passwordless technologies - some are better suited for consumer use, while others are designed primarily for workforce environments.
- Call centers have long been a clunky fallback for verifying identity - expensive and prone to human error.
- SMS one-time passwords (OTPs) remain widely used despite being one of the least secure options on the list.
- Passkeys are gaining traction as a modern, cross-platform replacement for passwords - especially in the consumer space.
- Hardware tokens are still popular in enterprise environments, particularly for high-risk access control.
- App-based authentication has become the go-to for many organizations balancing usability and cost.
- Email-based authentication is a common quick fix - simple to roll out, but risky when email accounts are compromised.
- Biometrics have gone now mainstream - used everywhere from banking apps to airport gates.
We’ve compared them below:
Comparison Table: Passwordless Authentication Solutions
While several passwordless authentication solutions offer heightened convenience or improved security over others, biometrics stand out when it comes to identity assurance - the ability to confidently confirm that the person logging in is the same person who originally enrolled. Methods like SMS OTPs, email links, and passkeys may verify that a device or account is in use, but they don’t confirm who is behind the screen.
In contrast, biometric authentication links a real, living person to their digital identity. By using unique physical traits like a user’s face or fingerprint to create a biometric identity, it becomes significantly harder for fraudsters to impersonate legitimate users or take over accounts. This direct connection between a person and their biometric ID makes this technology the most reliable option for organisations that need to know - and not just assume - who they’re letting in.
You can access our dedicated blog on the different types of passwordless authentication solutions here.
The Evolution of Biometrics in Authentication
Biometrics have become an everyday part of modern digital life. From unlocking smartphones to authenticating payments, biometric verification is no longer futuristic - it’s expected.
But how biometric data is handled is just as important as what it does. The method used to process and store biometric data can have a major impact on security, privacy, and usability.
There are three primary models for biometric authentication, each with its own strengths and weaknesses. These are local, centralized, and decentralized biometric systems.
Note that centralized and decentralized biometric systems are together called third-party biometrics.
What are Local (Device-Native) Biometrics?
In this model, biometric data - such as a fingerprint or facial template - is processed and stored on the user’s device. This includes solutions like Apple FaceID and Android Biometrics.
- Pros: Strong privacy; data never leaves the device.
- Cons: Limited usability and reduced security. Biometrics are tied to the operating system; an iOS user cannot use their FaceID to authenticate on an Android device. Less secure - an app has no way of telling that the person registered to FaceID is the same person that originally signed up for their account.
What are Centralized Biometrics?
Here, biometric templates are stored and authenticated on a central server (usually in the cloud). This model enables consistent authentication using a user’s biometric ID across devices.
- Pros: Works across multiple devices and platforms. The facial template used to open an account is tied to it - only that face can open that account.
- Cons: Less privacy. Storing biometric data centrally introduces significant privacy and security risks - if a server is compromised or hacked, the biometrics are.
What are Decentralized Biometrics?
Decentralized biometrics is a modern approach to authentication that uses cryptography and other privacy-preserving techniques to offer the best of both worlds: a centralized system, with its security and convenience, but with the privacy that a local system the privacy of local biometrics and the security and convenience of centralized systems.
Instead of storing full biometric templates on a device or a single server, decentralized systems use techniques like sharding or secure Multi-Party Computation (sMPC) to split and protect biometric data across different systems.
- Pros: Strong privacy and security when implemented correctly. Works across platforms and devices. No biometric data is ever stored or shared.
- Cons: Many so-called “decentralized” systems still don’t actually protect privacy. Still new to many organizations, so trust and understanding can be low.
Comparison Table: Types of Decentralized Biometrics
Below is a comparison of the three approaches:
Local vs Third-Party Biometrics
The biggest difference between local and third-party (centralized and decentralized) biometrics is this:
- Local biometrics (like FaceID) only unlock the device. The bank or service has no idea who set it up.
- Third-party biometrics link your biometric to your actual account, creating a secure, verifiable connection between you and your digital identity.
For a more detailed explanation of the different types of biometrics, you can read our biometrics white paper.
Types of Decentralized Biometrics
There are two main ways decentralized systems try to protect biometric data:
Sharding
Biometric data is split into pieces and stored across different servers. During authentication, each server matches only part of the data. In theory, this means no one can reconstruct the full biometric unless the shares are combined.
The problem is that most of these servers are owned or controlled by the same vendor. So if that vendor - or a hacker - gains access to enough of them, they can piece the data back together.
Even a single compromised server could be used in a de-anonymization attack (matching fragments to public photos). This creates serious privacy concerns and may violate regulations like GDPR.
sMPC: Secure Multi-Party Computation
Keyless introduced a new approach to decentralized biometrics which uses sMPC, a cryptographic method that allows biometric data to be matched without ever being stored, reconstructed, or shared - not even with Keyless.
The underlying principle of sMPC is often illustrated by the “Millionaire’s Problem”: two millionaires want to know who is richer - without revealing how much either one is worth. sMPC solves this by allowing parties to compute a result without ever revealing their individual inputs.
Applied to biometrics, this means a user’s fresh facial scan can be matched (on a server) against a biometric template that has been transformed (on the user’s device) into unrecognizable cryptographic data, without either side ever revealing the actual data. Keyless matches the authentication template with the enrollment template without seeing the biometric information within. It proves identity without exposing it.
This is called Zero-Knowledge Biometrics™.
- Biometric data stays private at all times - in use, at rest, and in transit.
- Even if systems are hacked, there’s nothing usable to steal as data is processed in transformed format.
- Users don’t need to re-enroll if they lose their device, and accounts can’t be hijacked using local FaceID-style tricks.
We explain this in more detail in our technical white paper - access it here.
UX vs. Security vs. Privacy – The “Golden Triangle”
One of the biggest challenges in authentication is balancing three competing priorities: user experience (UX), security, and privacy. Most solutions force organizations to compromise - improving one often means weakening another.
This tension is what we call the Golden Triangle of Authentication.
The Golden Triangle Explained
- Security: The ability to prevent account takeovers, stop phishing, and defend against spoofing and deepfakes.
- Privacy: Ensuring that biometric data is never stored, shared, or exposed—keeping users in control of their identity.
- User Experience (UX): Making the authentication process fast, effortless, and seamless for users.
Striking the right balance is crucial. Strong security is essential, but if the process is too slow or frustrating, users will abandon it. If privacy isn’t respected, users and regulators will lose trust. And if UX is prioritised too heavily, it can open the door to fraud.
A fourth and fifth element to add to this mix are cost and integration. While these factors may not directly impact the end user, they’re often just as important to decision-makers within an organisation.
- Cost: Authentication that’s secure but unsustainable to run won’t scale. Technologies that reduce the need for OTPs, password resets, and support overhead can drive real operational savings - while still improving user experience.
- Integration Time: Even the most secure, private, and user-friendly solution loses appeal if it takes months to deploy. Rapid integration - via SDKs, APIs, and flexible deployment models - can make or break a project’s success.
The best biometric authentication solutions strike the right balance across all five: security, privacy, user experience, cost-efficiency, and ease of integration.
Deployment Models and Real-World Examples
When adopting passwordless authentication - especially biometric solutions - how you deploy it is just as important as what you deploy.
Modern biometric systems like those powered by Zero-Knowledge Biometrics™ are designed to be flexible and scalable, supporting a wide range of deployment models.
Keyless Deployment Options
- Cloud: Ideal for fast, scalable rollouts without needing to manage infrastructure. All security updates and compliance requirements are handled by the vendor.
- On-Premises: Often used in regulated industries like banking, where sensitive operations need to stay within the organization’s infrastructure.
- Hybrid: Combines the benefits of cloud scale with local control, allowing sensitive data to stay on-prem while leveraging cloud performance.
- SDKs and APIs: Easily integrated into mobile apps, web platforms, and shared devices—enabling both customer and workforce authentication.
Visit our Documentation Hub for full integration guides on how to integrate Keyless in apps and SSO flows.
Keyless Case Studies
Keyless has been trusted by banks, fintechs, crypto exchanges, gaming providers, and digital wallet platforms since 2019. Over that time, we’ve built a global customer base delivering both consumer-facing and workforce authentication solutions across four continents.
Our written case studies include:
- One of Europe’s largest banks replaced OTPs with facial biometrics for transaction approvals, reducing support tickets and improving user experience.
- A leading European finance automation platform achieved PSD2 compliance and improved security by replacing outdated SMS OTPs with Keyless’ facial biometric authentication.
- A major Italian university, in partnership with Cisco, transformed its exam process during the COVID-19 pandemic by enabling secure remote exams with privacy-preserving biometric authentication.
The Cost of Biometric Authentication Technologies
Switching to biometric authentication may seem like a significant step—but when weighed against the ongoing costs of traditional methods, it often delivers a fast and measurable return on investment.
Legacy authentication methods like passwords, PINs, and OTPs are not only less secure—they’re expensive. Biometric authentication helps organisations cut costs while improving security and user experience.
Direct Cost Savings
- Fewer password resets: Biometric login eliminates the need to remember anything, drastically reducing support centre tickets and reset requests.
- No more OTPs: SMS OTPs are not only vulnerable to interception and SIM swapping - they also come with a per-message cost. Biometric authentication removes this dependency.
- Lower re-verification costs: Re-KYC or manual account recovery processes are slow and expensive. With biometrics, users can re-authenticate or recover access instantly with a selfie - removing the need for re-KYC flows.
- Reduced fraud losses: Biometric systems that provide true identity assurance help prevent account takeovers, synthetic identity fraud, and credential-based attacks.
Although implementing biometric authentication may require upfront investment, the total cost of ownership is typically far lower than maintaining insecure and fragmented legacy systems.
Keyless clients consistently report reduced fraud losses, lower operational costs, and improved user retention. Most organisations see clear ROI within the first 12 months of deployment - while also strengthening security and privacy protections.
Future Outlook: Where Is This Headed?
Biometric authentication has already transformed how we think about identity - but the most exciting developments are still ahead.
Biometric Use Expanding Across Channels
Biometrics are moving beyond the mobile app. They’re now being used to authenticate users across:
- Web browsers
- Desktop environments
- Shared devices (like kiosks and terminals)
- Remote access platforms (VPNs and VDIs)
The future of biometric authentication is channel-agnostic—designed to work wherever users are, on whatever device they’re using.
AI-Driven Attacks Require AI-Resilient Defences
With generative AI making it easier than ever to create deepfakes and synthetic identities, biometric systems must evolve in parallel. Passive liveness detection, injection attack prevention, and behavioural signals will become core to any biometric platform that wants to stay ahead of these threats.
Solutions that can’t detect deepfakes in real time - or that rely solely on device-native biometrics - will struggle to keep up.
Keyless’ liveness is deepfake-resistant, stopping both presentation and injection attacks. Read our related press release here.
Beyond Authentication: Identity as Infrastructure
Biometrics won’t just be about logging in—they’ll become the invisible infrastructure for identity across the digital world.
This is already starting to happen, and it’s only going to accelerate. In the near future, biometrics will underpin:
- Digital identity wallets
- Biometric-based signing and encryption
- Frictionless payments and access control
- Secure remote onboarding
Imagine a world where you no longer need to remember passwords, carry hardware tokens, or answer security questions. A world where your face - or any unique biometric - is your secure, private, and portable identity across all channels and services. A world that is Keyless.
Keyless offers innovative solutions, including advanced biometric authentication with privacy safeguards, continuous authentication to prove user identity, and modern MFA for enhanced security. By combining these strategies, organizations can significantly reduce the risk of ATO fraud and protect both their business and their customers.
You can reach out to our support team if you have any questions regarding how to integrate our biometric solutions into your system or request a demo of our technology here.
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