What to Know About PKI Smart Card Authentication

Companies and governments around the world are rapidly adopting PKI smart cards, especially for identity management. These tiny chips can be found in a multitude of applications including ID cards, credit/debit cards, SIM cards, security keys, and more.

Smart cards are often used in physical security tokens (otherwise known as “security keys”) like the Yubikey. Enterprises use them to render their networks impervious to over-the-air attacks and virtually eliminate phishing.

For the purposes of this article, our references to smart cards will primarily be in regard to security keys. They’re a common choice for organizations that want to deploy supplementary cyber security measures.

What is a PKI Smart Card?

Smart card and PKI smart card are used interchangeably in the context of enterprise network security. Just about every smart card is capable of being integrated with a public key infrastructure (PKI) because they all share the same fundamental component – a secure cryptoprocessor chip.

In fact, smart cards often have the capacity to perform some of the basic functions of a PKI by themselves (creating private keys, storing digital certificates, etc.). They don’t, however, natively have a convenient graphical user interface or the capacity to be managed at scale.

To overcome that obstacle, organizations use a smart card management system (SCMS) like the SecureW2 system. SCMSs offer the ability to integrate smart cards into your PKI so that you can simultaneously configure multiple devices and enroll them for x.509 digital certificates.

How PKI Smart Card Authentication Works End to End

PKI smart card authentication combines certificates, hardware-bound keys, and a centralized trust model to rigorously verify users and devices. Here’s what that looks like when we break down the key building blocks and process flow.

The PKI trust chain (CA, intermediates, revocation)

Public key infrastructure relies on a trust chain that starts with root certificate authority (CA) and often includes one or more intermediate CAs. A trusted CA issues each smart card certificate, and systems validate that the issuing CA is part of this chain.

During authentication, the system checks the certificate for expiration and status via mechanisms such as certificate revocation lists (CRLs) or Online Certificate Status Protocol (OCSP) to verify it has not been revoked. This strategy lets enterprises centralize control over which smart cards and identities remain trusted over time.

Here are the steps in that process:

1. Root and intermediate CA define what the environment trusts.
2. Smart card certificates are signed by a CA inside that chain.
3. Expired or revoked certificates are rejected at authentication.
4. CRL and OCSP can provide real-time revocation information.

Smart card user authentication flows

In a typical flow, the user inserts their smart card and grants access by either a PIN or biometric input. The application or OS sends a cryptographic challenge that only the card’s private key can sign, and the smart card generates a digital signature without the need to expose the key.

The server or service then validates the signature using the certificate’s public key and then verifies the certificate itself against the trust chain. If both checks are passed, and the identity maps to a known account or device record, user access is granted.

Here are the steps in that flow:

1. Users inserts card and unlocks it locally.
2. System sends a challenge tied to the specific session or request.
3. Smart card then signs the challenge with its private key.
4. Finally, the server verifies the signature and certificate before granting access.

Mutual TLS and smart card-based web access

For web and VPN use cases, smart cards are frequently used as client certificates in mutual Transport Layer Security, or TLS. The browser or VPN client presents the certification from the smart card during the TLS handshakes, and the server validates it before allowing access to protected resources. This creates a stronger, phishing-resistant channel where both client and server authenticate each other using PKI.

The steps are:

1. The smart card certificate is selected as a client certificate.
2. TLS handshake includes client certificate presentation.
3. Server validates the certificate against trusted CAs.
4. Access to apps or VPN is then tied to that authenticated identity.

Why Use a PKI Smart Card?

The primary purpose of a smart card is identity authentication. The smart card in a credit card confirms that the card is unique and legitimate just as the smart card in a government PIV access card confirms that the bearer is authorized for access to restricted areas.

All authentication methods are greatly strengthened by having multiple factors of authentication (MFA). Simply swiping your debit card isn’t enough; you have to also put in a PIN for a second factor of authentication to make purchases.

Some smart card devices, like the Yubikey security key, can perform multiple factors of authentication themselves. Using private keys or one-time-passwords, requiring physical touch to send the authentication request, and biometric scanning of fingerprints are three different factors of authentication Yubikey is capable of. The device is incredibly effective for preventing unauthorized access.

How to Configure a PKI Smart Card for 802.1x Authentication

There’s no single process that can configure every smart card for 802.1x authentication since there are many manufacturers and many different devices that smart cards can be found in. For this section, we use Yubico’s titular Yubikey as an archetypal example of configuring security keys.

Yubikeys have a predefined list of applications they can integrate with, though they can be coaxed into working with many other services either directly through API or indirectly through integration with a PKI. By loading the Yubikey with x.509 certificates tied to an external identity provider, the Yubikeys can be used to authenticate most any web-based service.

In our capacity as an official Yubico Partner, SecureW2 has engineered a solution that massively enhances the potential integrations of a Yubikey. Instead of having to manually configure each key via command line interface, our software allows you to push automatic configuration profiles to each device for self-enrollment of certificates and integration into our enterprise cloud PKI solution.

Here’s a short video that illustrates how easy it is for the end user to set up their Yubikey. The guided onboarding process prompts the user to set up a PIN and PUK (with customizable complexity requirements).

Once tied into your PKI via SecureW2, Yubikeys can be used for 802.1x authentication for access to Wi-Fi, VPN, desktop login, and virtually any web app with support for certificates (and you can continue using the intrinsic private key generator for services that don’t support certificates).

Managing PKI Smart Cards in the Enterprise

Managing PKI smart cards at scale requires industrializing the way you issue, track, and retire credentials so that security can keep pace with growth and not become a barrier or blocker.

Enrollment, distribution, and de-provisioning

Smart card programs succeed when enrollment can be streamlined, predictable, and carefully tied to identity lifecycle events. Centralizing issuance through HR/IT workflows guarantees every new hire gets a card, backing certificate, and policy-aligned profile.

Self-service portals and automated provisioning cut help desk workloads while also enforcing more consistent configuration. Equally important, de-provisioning must be immediate when people leave or change roles to ensure no active certificates remain associated with former users or devices.

The steps are:

• Integrate enrollment with HRIS and identity governance
• Use automated issuance and renewal versus manual processes
• Support secure remote or distributed card distribution
• Trigger revocation automatically on termination or role change

Certificate status and revocation checks

Even well-issued smart cards can potentially become risky if certificate status isn’t validated and enforced in real time. Every authentication should verify that a certificate remains unexpired, unrevoked, and issued by a trusted CA. 

Online checks using OCPS or frequently updated CRLs make sure compromised/lost cards can’t be used. This closes the gap between business/policy decisions (e.g. firing an employee) and their impact at the authentication layer.

• Enforce expiry checks on every auth decision
• Use CRLS or OCSP to block revoked certificates
• Apply different validity periods to different risk profiles: higher risk should drive shorter cert lifetimes
• Monitor failures to detect widespread trust or CA issues

Auditing, reporting, and policy enforcement

Once smart cards are widely deployed, visibility becomes absolutely critical for both security and compliance. Centralized logs must be used to show which cards authenticate where, when, and under which policies. Reporting can help identify stale, underused, or misconfigured credentials that should be either rotated or revoked.

Policy engines can enforce requirements such as strong PINs, specific key lengths, or particular assurance level for higher-risk systems. Together these capabilities turn PKI smart cards from a one-time rollout to continuously managed control.

The Best Enterprise PKI Smart Card Management System

Despite being geared towards enterprise cybersecurity, PKI smart cards rarely have the capacity to be managed at scale. Insufficient smart card management can lead to vulnerabilities more dangerous than simply not using the cards at all, which is why a robust SCMS is important.

Fortunately, the SecureW2 SCMS can be integrated into your existing network infrastructure or be included as part of our larger Cloud PKI solution. We help organizations of all types secure their network perimeter with digital certificates and MFA provided by security keys. Schedule a demo to learn more.