As the popularity of mobile credentials grows and more users adopt it within the organization, IT managers should consider an important usability aspect…certificate validation speed and availability. In this blog, we will discuss what it takes to ensure mobile device certification validation is fast and scalable to handle the ever growing needs of mobile based certificate validation.


This blog will help you learn how to build a fast and resilient credential validation infrastructure. It desribes:

  1. Basics of certificate validation
  2. Impacts of mobile device certificate validation
  3. Considerations for adding speed and resiliency

Basics of Certificate Validation

To understand ways to improve certificate speed, we need to understand the process of how certificate validation works. To ensure a certificate is valid and has not been revoked, the certificate is electronically checked against a file known as a Certificate Revocation List (CRL) each time it is used. This is very important but can be a timely process.  This CRL contains all certificate information (in this case, the certificate information) that have been revoked. If the certificate information is on this list, then the certificate is deemed to be revoked and the certificate cannot be used.

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To obtain the CRL information, the computer that is verifying the card performs what is known as a certificate validation process. During this process, the CRL is downloaded from the Certificate Authority (CA) and then the certificate is checked against the CRL file to determine whether the certificate is in good standing. If the certificate is in good standing, then the transaction can occur.

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Drawbacks of CRL Validation

Although the CRL validation technique works to validate the card, it is very slow and is prone to a single point of failure. This is due to the size of the CRL and the fact that each computer must download a fresh copy of the CRL list.

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In enterprise environments, this leads to very slow validation times and outages. When this occurs, the end users cannot use their certificate for authentication…which leads to the end user being locked out of their computer. This can quickly become a huge problem for the enterprise.

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Impacts of Mobile Device Certificate Validation

The biggest impact has to do with the number of certificates that now must be validated by the enterprise. As we will see below, there are numerous factors that could drastically change the validation requests that occur in the enterprise during typical work day.

1 Person – many devices

Think of how many devices you own? I know personally, I have two laptops, one phone, and one tablet. Some people have two phones, two laptops and a tablet or two. Now, multiply the number of devices by the employees, partners and external users across the enterprise. That’s a lot of devices that will need be validated if a person wants to use their certificate on any of their devices. This drastic increase in validation transactions can bring a traditional validation architecture to a halt.

Upgrade cycle

Each year, the mobile device vendors create a better phone, tablet or ultra cool laptop than the year before…encouraging the end user to upgrade their multiple devices. Because of this upgrade cycle, users are constantly getting new devices which require new certificates… which as you can imagine is doubling the amount of certificates that are being generated and revoked which causes your CRL to grow and grow which makes the validation slower and slower.

1 Certificate – multiple devices

With new certifiate synchoronization technologies, a user’s certificate on one device can be syncronized other devices. This occurs when a user wants to read an encrypted email on their laptop and smart phone. Although this makes it easier to check your secure email on any device you own, it also increases the validation workload because now the certificate is being used in multiple places.

Considerations for Adding Speed and Resiliency

To overcome the limitations of the CRL Validation technique, a technology known as Online Certificate Status Protocol (OCSP) was developed. With OCSP, the CRL list is replaced with a micro file, known as an OCSP response that only contains the information for one card. This greatly streamlines the PIV validation process for the computer and network since now only a very small file is downloaded and processed.


The OCSP architecture is significantly faster since each workstation only downloads the micro file (OCSP Response). Additionally, the enterprise is no longer vulnerable to a single point of failure since the OCSP technology can be distributed to different areas of the enterprise.

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  • Faster transactions- Using the micro file OCSP technology, certificates can be validated instantaneously whereas the CRL Validation technique could take minutes (or longer) and consume large amounts of network bandwidth.
  • “Always there” validation-With CRL Validation, a single point of failure exists. For example, if the network is interrupted and CRL list cannot be downloaded, then all of the computers needing the list will fail to validate the PIV card. This could result in locking end users out of their computers for hours. With OCSP technology, the validation elements can be distributed throughout the environment so the computers have the ability to validate against different servers thus providing “always there” validation.
  • Scalable- The distributed design of OCSP technology enables enterprises to finely tune and optimize their PIV validation capability. For example, as their PIV Card user base grows, they can add more OCSP processing power with additional OCSP servers.

Implementation Approaches

Adding speed and resiliency has been made much easier thanks to the adoption of OCSP by many software vendors. For example, Apple and Microsoft now provide OCSP clients in their operating systems out of the box. Enterprises also now have easy to deploy options to immediately add OCSP power to their internal networks. For example, the HID ActivID Validation Authority  implements OCSP and other fast validation protocols and is easy to install as a hardware device or as software.


It is clear that the NIST Derived Credential publications, industry support for Virtual Smart Cards and general need for strong MFA will continue to drive the need for PKI on mobile devices. Enterprises must be ready for this growth to ensure the validation architecture continues to be as robost and fast as possible.