Physical Badge Access & Passkeys: Technical Guide

Modern security is defined by the dissolution of old boundaries. For decades, organizations operated with a clear demarcation between physical security—guards, locks, and access badges - and logical or cybersecurity—firewalls, passwords, and network protocols. These two domains were managed in separate silos, with distinct teams, policies, and objectives.

Today, that separation is no longer viable. The proliferation of network-connected physical systems, from security cameras to smart door locks and HVAC controls, has created a deeply interconnected cyber-physical environment. This convergence means that a vulnerability in one realm can cascade into a catastrophic failure in the other. A cyberattack can unlock physical doors, and a stolen access card can lead to a server-room breach. Consequently, a holistic, converged security strategy is no longer a forward-thinking trend but a foundational requirement for any robust security posture, driving significant investment in unified platforms.

This new reality presents a challenge for workforce authentication. Employees, whether in-office, remote, or in hybrid roles, require access to a rapidly expanding portfolio of cloud and SaaS applications. This distributed access model creates a vast and complex attack surface. The traditional username and password, even when augmented with legacy multi-factor authentication (MFA) like SMS codes, remains the weakest link - a primary vector for phishing, credential stuffing, and account takeover attacks. In response, the industry is undergoing a shift towards passwordless, phishing-resistant authentication. Market forecasts project the passwordless authentication market to grow from over $18 billion in 2024 to more than $60 billion by 2032, with 87% of enterprises already deploying or in the process of deploying passkeys for their workforce.

Amidst this technological evolution lies a powerful, often-overlooked asset: the physical employee badge. Ubiquitous in nearly every medium to large organization, this simple card is the key to unlocking a more secure and frictionless digital future.

The central purpose of this article is to provide a neutral, deeply technical analysis of the architectural patterns available for integrating these physical badges with passkey-based authentication. Specifically, this analysis focuses on custom-built SaaS applications in a workforce context, where reliance on a traditional, on-premises corporate Identity Provider (IdP) is not a given. The following sections will dissect three distinct paths to this integration, evaluating their technical components, security models, and the critical trade-offs between them.

Before architecting a converged system, it is essential to establish a granular understanding of its fundamental components. The capabilities of the physical token and the mechanics of the digital credential dictate the available integration paths. A failure to appreciate the nuanced differences between a simple identifier and a true cryptographic authenticator can lead to flawed architectural decisions.

Employee badges are not a monolith; their underlying technology spans a wide spectrum of complexity and security. Understanding where a specific badge falls on this spectrum is the first step in determining its potential role in a modern authentication system. The following tables provide a detailed breakdown of this evolution.

Organizations upgrading from UID-based access systems to secure authentication tokens typically follow this path:

1. Basic UID Badge → used for physical access only.
2. Secure NFC Badge → adds encryption for access control but still not suited for digital authentication.
3. PKI Smartcard (PIV) → adds digital certificate-based access (VPNs, signed emails), requires middleware.
4. FIDO2 Smartcard → enables passwordless login via WebAuthn, can also combine with physical access functions.
5. Platform Passkeys → future vision where physical tokens become optional, but convergence is best served when one device handles both physical and logical access.

This detailed breakdown clarifies the distinction between a simple identifier and a cryptographic authenticator, which is the single most important concept in this analysis. A basic RFID badge can only provide a UID, which can at best serve as a username hint to initiate an authentication flow. It cannot participate in the cryptographic challenge-response that is the heart of WebAuthn. A FIDO2 smart card, conversely, is designed precisely for this purpose. This fundamental difference is what gives rise to the three distinct architectural patterns that follow. Options 1 and 2 are essentially workarounds designed to accommodate the limitations of identifier-only badges, while Option 3 represents the native integration of a true authenticator.

With a clear understanding of the underlying technologies, we can now explore the three primary architectural models for integrating physical badges with passkey authentication for a workforce SaaS application. Each path presents a unique set of trade-offs in security, cost, user experience, and complexity.

This model is conceptually the most abstract. The physical badge does not store a passkey itself. Instead, it functions as a low-assurance token used to authorize a centralized service to perform a high-assurance authentication on the user's behalf. The passkey's private key is not held by the user but is stored and managed within a Hardware Security Module (HSM) operated by a "Credential Vault" provider.

1. User Action & Identification: An employee taps their standard RFID/NFC badge on a reader connected to their workstation. The reader captures the badge's static UID.
2. Request to Vault: A client-side component sends the UID to a proprietary API endpoint hosted by the Credential Vault provider.
3. Server-Side WebAuthn Initiation: The Vault service receives the UID, looks up the associated user account, and then initiates a WebAuthn authentication ceremony with the target SaaS application (the Relying Party) on behalf of the user. The SaaS application returns a standard authentication challenge.
4. HSM-Based Signing: The Vault service passes this challenge to its internal HSM. The HSM securely stores the private key component of the user's passkey for that specific SaaS application. The HSM performs the cryptographic signing operation on the challenge and returns the resulting signature to the Vault service. The private key never leaves the HSM's secure boundary.
5. Authentication Completion & Token Issuance: The Vault service completes the WebAuthn flow by sending the signed challenge back to the SaaS application. The SaaS application verifies the signature using the user's public key (which it has on file) and, upon success, issues an authentication session token (e.g., a JSON Web Token).
6. Session Delivery: The Vault service forwards this session token back to the user's browser, which can then use it to establish an authenticated session with the SaaS application, completing the login.

• Advantages:
  • Leverages Existing Infrastructure: This model's primary appeal is its ability to work with the most common and inexpensive RFID/NFC badges already deployed in an organization, avoiding a costly and disruptive hardware refresh.
  • Highly Seamless User Experience: It can provide a true "tap-and-go" login. From the user's perspective, a single tap on the badge reader logs them directly into the application, representing extremely low friction.
  • Centralized Management: All passkey credentials are created, stored, and managed within the provider's ecosystem. This can simplify administrative tasks like revocation and policy enforcement.
• Disadvantages:
  • Proprietary and Closed-Loop System: This architecture effectively turns the badge and vault provider into a new, proprietary Identity Provider (IdP). The organization becomes deeply dependent on this single vendor for a critical function. Such "closed-loop" systems are inherently inflexible and create significant vendor lock-in, making future migrations difficult and costly.
  • Extreme Trust Requirement: The security of the entire system hinges on the trustworthiness and competence of the Vault provider. Since the provider's HSMs hold the private keys for all users across all applications, a compromise of the provider would be catastrophic.
  • High Cost and Complexity: This is not a simple solution. It requires either building or subscribing to a highly complex, mission-critical service that includes expensive HSM infrastructure, sophisticated software, and high-availability operations.
  • Deviation from WebAuthn Principles: This model fundamentally breaks with the core principle of WebAuthn, which is user-possessed, client-side authentication. The authenticator is server-side, which is an anti-pattern for general web authentication. As noted in the initial query, this approach is generally not recommended for authenticating to a standard Web SaaS application.

This model represents a pragmatic compromise. It uses the existing, simple badge not to authenticate, but to streamline and accelerate a standard WebAuthn flow. A piece of software installed on the user's computer acts as a "bridge" between the physical badge reader and the web browser.

1. User Action & Local Detection: An employee taps their basic RFID/NFC badge on a standard USB reader connected to their workstation.
2. Local Listener Agent: A lightweight background service or daemon running on the operating system (e.g., using the PC/SC API) is listening for smart card reader events. It detects the badge tap and reads the UID from the card.
3. Agent-to-Extension Communication: This local agent communicates the captured UID to a companion browser extension. This is typically achieved using the browser's Native Messaging Host API, which allows a sandboxed extension to exchange messages with a pre-registered native application.
4. Username Pre-fill and Flow Initiation: The browser extension contains logic to map the received UID to a specific username. Upon receiving the UID, it injects the corresponding username into the login form of the SaaS application. Modern login forms can also use the autocomplete="webauthn" attribute on input fields to signal to the browser that a passkey flow can be initiated for the autofilled user. The extension can then programmatically trigger the start of the passkey authentication process.
5. Standard WebAuthn Ceremony: From this point forward, a completely standard WebAuthn authentication ceremony takes place. The browser prompts the user to use their registered passkey authenticator. This could be the computer's platform authenticator (e.g., Windows Hello, macOS Touch ID) or a separate roaming authenticator (like a YubiKey or even the user's phone). The user completes the authentication gesture (e.g., fingerprint scan), and the login is completed as per the standard flow. The badge's role is now finished.

• Advantages:
  • Standards-Compliant Authentication: The most significant benefit is that the actual cryptographic authentication is a pure, unadulterated WebAuthn flow. The security model relies on the proven principles of FIDO2, not a proprietary workaround. The badge tap is purely a user experience enhancement.
  • Leverages Existing Hardware: Like Option 1, this approach works with the existing fleet of basic RFID/NFC badges and inexpensive USB readers.
  • Improved User Experience: While not a single-tap login, it significantly reduces friction. The user is saved from having to remember and type their username, which shortens the login process and reduces potential for error.
• Disadvantages:
  • Software Deployment and Maintenance: The primary drawback is the operational overhead. This architecture requires deploying, configuring, and maintaining two separate pieces of software—a native OS-level agent and a browser extension—on every single employee workstation. This can be a significant burden for IT departments, who must manage updates, troubleshoot compatibility issues with different OS and browser versions, and handle security patching.
  • Architectural Fragility: The communication channel between the hardware driver, the native agent, and the browser extension is a custom-built bridge. This "glue" can be brittle and is susceptible to breaking when the operating system or browser releases updates, leading to a poor and unreliable user experience.
  • Incomplete Solution: This is not a "tap-and-go" solution. The user must still perform a second, distinct action to complete the authentication with their actual passkey. The badge tap only automates the first step of the login process.

This is the most direct, secure, and standards-aligned architecture. In this model, the employee badge is itself a FIDO2-compliant smart card. It is a true cryptographic authenticator that can participate directly in the WebAuthn ceremony without any intermediary software.

1. User Navigation: An employee navigates to the login page of the SaaS application. The application is configured to support passkey authentication.
2. WebAuthn Initiation: The user clicks a "Sign in with a passkey" button, or the browser's Conditional UI (autofill) automatically detects available passkeys and presents them in a non-modal prompt. The browser's JavaScript calls

navigator.credentials.get() to start the authentication ceremony.

1. Authenticator Interaction: The browser, via the operating system, prompts the user to present their security key. The employee either taps their FIDO2 badge on an integrated NFC reader or inserts it into a connected smart card reader.
2. On-Card Cryptographic Signature: The browser sends the challenge from the SaaS application to the badge. The secure element within the badge uses its internally stored, non-exportable private key to sign the challenge. Depending on the Relying Party's policy and the card's capabilities, this step may also require user verification, such as entering a PIN on the workstation or placing a finger on a biometric sensor embedded in the card itself.
3. Authentication Completion: The badge returns the signed response to the browser, which forwards it to the SaaS server. The server verifies the signature, and the user is securely logged in. The entire process is orchestrated by the browser and operating system using standardized FIDO protocols.

• Advantages:
  • Highest Security and Standards-Alignment: This is the "gold standard" approach for converged access. It uses the FIDO2 and WebAuthn standards exactly as they were designed, providing the strongest possible protection against phishing and man-in-the-middle attacks. The user is in physical possession of the hardware token containing their private key.
  • Architectural Simplicity and Robustness: This model is elegant in its simplicity. There are no custom agents, browser extensions, or proprietary bridges to develop and maintain. The authentication flow relies on the highly robust and well-maintained APIs and drivers built into modern operating systems and browsers.
  • True Security Convergence: This architecture delivers on the promise of a truly converged credential. A single, manageable physical token is used to grant access to both physical spaces (doors) and logical resources (applications), simplifying the user experience and the security model.
• Disadvantages:
  • Significant Hardware Cost: The most substantial barrier to this approach is the upfront investment. It requires replacing an organization's entire fleet of basic RFID/NFC badges with more expensive FIDO2-compliant smart cards. Depending on the existing infrastructure, it may also necessitate upgrading physical door readers to be compatible with the new cards.
  • Complex Credential Lifecycle Management: Managing the full lifecycle of cryptographic credentials for a large workforce is more involved than managing a simple list of UIDs. Processes for secure issuance, key rotation, certificate renewal (if PKI is also used), and especially revocation and recovery become more critical and complex.
  • User Experience Nuances: While highly secure, the user experience can introduce different points of friction. If the card requires a PIN for user verification, it reintroduces a "what you know" factor that must be remembered. The physical action of inserting a card into a reader may be perceived as less fluid than a simple contactless tap, depending on the specific hardware deployed.

The decision between these three architectural paths is not merely technical; it is a strategic one that balances competing priorities. Option 1 prioritizes a seamless user experience and the use of existing hardware but does so by creating a high-cost, high-risk proprietary dependency that deviates from open standards. Option 2 also leverages existing hardware and improves the user experience while adhering to authentication standards, but it shifts the cost and complexity to the difficult and often-underestimated problem of managing software on every endpoint. Option 3 prioritizes security, robustness, and adherence to open standards above all, accepting a higher upfront hardware cost in exchange for a simpler, more future-proof architecture with lower long-term maintenance overhead. There is no universally "correct" choice; the optimal path depends on an organization's specific risk tolerance, budget, existing infrastructure, and IT support capabilities.

Choosing the right architecture requires a clear, side-by-side comparison of these trade-offs. This section provides a framework to distill the complex analysis into an actionable format for technical leaders and to address the practical, real-world challenges of implementation.

The optimal path for an organization depends on its primary business drivers.

• If your primary driver is minimizing upfront capital expenditure and leveraging your existing badge fleet, then Option 2 (Desktop Bridge) is the most pragmatic choice. It provides a tangible improvement in user experience and adopts a standards-compliant authentication core without requiring a large hardware investment. However, this path should only be chosen if the organization has a mature and robust endpoint management capability, as the success of this model hinges on the ability to reliably deploy and maintain the necessary client-side software.
• If your primary driver is achieving the highest level of security, aligning with industry best practices, and building a future-proof, low-maintenance architecture, then Option 3 (Converged Credential) is the clear strategic winner. This approach fully embraces open standards, eliminates brittle custom software, and provides the strongest phishing-resistant protection. The upfront hardware cost is an investment in long-term security and operational simplicity.
• If your primary driver is delivering a "magical," frictionless tap-to-login experience above all other considerations, then Option 1 (Centralized Vault) is the only one that truly provides it. However, this path must be approached with extreme caution. It introduces significant strategic risk through vendor lock-in and demands an exceptionally high level of trust in the provider's security architecture and operations. For most open web and SaaS applications, the proprietary, closed-loop nature of this model makes it a less desirable choice compared to standards-based alternatives.

A successful passkey strategy extends far beyond the login flow; it must encompass the entire identity lifecycle. The choice of architecture has profound implications for how users are onboarded, how access is revoked, and how accounts are recovered.

• Issuance and Onboarding: For a new employee, the process differs significantly. In Options 1 and 2, onboarding involves issuing a standard badge and then creating an entry in a database that maps the badge's UID to the user's account. In Option 3, the process is a formal FIDO2 registration ceremony, where the new FIDO2-compliant badge is used to generate a passkey that is then registered with the SaaS application. This process is more secure but also more complex to manage at scale.
• Revocation (Employee Termination): When an employee leaves, their physical access is always revoked in the central PACS. For logical access, the steps are:
  • Option 1: The vault provider must be immediately notified to disable or delete the credential stored in their HSM.
  • Option 2: The user's actual passkey (e.g., the one stored in their laptop's TPM via Windows Hello) must be revoked from the SaaS application's settings. The badge UID mapping becomes irrelevant once the underlying passkey is disabled.
  • Option 3: The public key associated with the employee's FIDO2 badge must be deleted from their user profile within the SaaS application, rendering the badge useless for logging in.
• Recovery (Lost or Stolen Badge): This is a critical failure mode that must be planned for. The implications vary drastically:
  • In Options 1 and 2, a lost badge is less critical for logical access, as it is only an identifier. The primary risk is unauthorized physical access. The user can still log in using their actual passkey authenticator.
  • In Option 3, a lost badge can be a major problem. If the FIDO2 badge is the only passkey registered for the user's account, they are completely locked out. This underscores a critical best practice for any enterprise passkey deployment: users must be required or strongly encouraged to register multiple authenticators. A robust policy would mandate that an employee registers both their FIDO2 badge (as a primary day-to-day authenticator) and a backup, such as their platform authenticator (Windows Hello/Face ID) or their phone, to be used for account recovery.

Ultimately, a successful passkey deployment is not just an authentication project; it is an identity and access management (IAM) project. The technical architecture for the login flow cannot be designed in a vacuum. It must be tightly integrated with a comprehensive strategy for provisioning, managing, and de-provisioning identities and their associated credentials throughout their lifecycle. This holistic view is essential for mitigating risks like account lockout and ensuring the long-term success and security of the system.

The journey to integrate physical access badges with modern digital authentication is a clear manifestation of two powerful, intersecting trends: the convergence of physical and cyber security and the inexorable industry-wide migration away from passwords. As this guide has detailed, organizations have three distinct architectural paths to choose from, each presenting a fundamental trade-off.

• The Centralized Vault offers a seamless user experience at the cost of proprietary lock-in and significant strategic risk.
• The Desktop Bridge offers a pragmatic, low-cost path to better UX while maintaining security standards, but introduces considerable software maintenance overhead.
• The Converged Credential offers the highest level of security and robustness by adhering strictly to open standards, but requires a significant upfront investment in hardware.

While each path represents a step toward a more secure, passwordless future, the long-term trajectory of enterprise security favors solutions built on open, interoperable standards. Architectures that embrace FIDO2 and WebAuthn natively—as exemplified by the Converged Credential model and, to a degree, the Desktop Bridge—provide the most robust and future-proof foundation. They empower organizations to build best-in-class security systems that leverage a competitive ecosystem of hardware and software, free from the constraints of a single vendor's closed-loop platform. For any organization building the next generation of workforce applications, embracing these open standards is not just a technical choice; it is a strategic commitment to a more secure, flexible, and interoperable digital world.