How to use Secure Certificate Pinning in Android & iOS Apps

Last updated November 6, 2023 by Appdome

Learn to Prevent Redirecting the Mobile User to a Malicious Site in Mobile apps, in mobile CI/CD with a Data-Driven DevSecOps™ build system.

What is Secure Certificate Pinning?

Certificate Pinning is the process of embedding a mobile app with valid SSL certificate for trusted servers. An application that pins a certificate or public key no longer depends on external elements such as DNS or intermediate/public certificate authorities, when making security decisions relating to a peer server’s identity.

The most common form of certificate pinning is embedding the server certificates inside the mobile app, to ensure that the server certificate is always trusted. This will prevent hackers from presenting modified fraudulent certificates to the mobile app in an attempt to redirect the mobile user to a malicious site. A host or service’s certificate or public key can be added to an application at development time, or it can be added upon first encountering the certificate or public key. The former – adding at development time – is preferred since preloading the certificate or public key out of band means the attacker cannot taint the pin by intercepting the session before the TLS handshake completes.


How Appdome Implements Secure Certificate Pinning?

Certificate Pinning is the practice of embedding the certificate(s) of the known trusted server(s) inside the mobile application (obfuscated and encrypted for protection). Each time a TLS session is initiated by either end, Appdome inspects the pinned certificate stored inside the app to make sure it matches that of the trusted server. In case of a mismatch, the session i not allowed.

When setting up Certificate Pinning, here are the Certificates expected for each evaluation scheme:

  • Strict Evaluation scheme: server certificate
  • Chain Evaluation scheme: Root CA cert + the intermediate certificate or/and the server certificate
  • Root Evaluation scheme: root CA certificate
  • Public Key Evaluation scheme: server certificate

Note: Appdome validates uploaded certificates before the build step. During this validation process, Appdome detects and alerts on known errors in the certificates, including expired certificates, invalid certificate format, missing certificates in the chain, non-valid Root certificate, and invalid files and file types. Appdome supports certificate file types such as .cer, .crt, .pem, .der or a .zip. It is important to remember that a single certificate file cannot contain multiple certificates. For entries requiring more than one certificate, each certificate must  be provided as a single file and then all files can be zipped together.

In addition, by defining Service Domain, mobile app developers can use a variety of methods to verify and pin certificates for specific domains. Each Service Domain can be configured by using * as a wildcard value, and can be applied to multiple domains.

Please be aware that Security Certificate Pinning and the Anti Bot Secure Certificate Pinning are mutually exclusive. Implementing them together will result in a conflict within the engine. Ensure to use only one method at a time to avoid potential issues.


Prerequisites for Using Secure Certificate Pinning:

To use Appdome’s mobile app security build system to Prevent Redirecting the Mobile User to a Malicious Site , you’ll need:

Prevent Redirecting the Mobile User to a Malicious Site on Mobile apps using Appdome

On Appdome, follow these 3 simple steps to create self-defending Mobile Apps that Prevent Redirecting the Mobile User to a Malicious Site without an SDK or gateway:

  1. Upload the Mobile App to Appdome.

    1. Upload an app to Appdome’s Mobile App Security Build System

    2. Upload Method: Appdome Console or DEV-API
    3. Mobile App Formats: .ipa for iOS, or .apk or .aab for Android
    4. Secure Certificate Pinning Compatible With: Obj-C, C+, Java, JS, C#, C++, Swift, Kotlin, Flutter, React Native, Unity, Xamarin, and more
  2. Build the feature: Secure Certificate Pinning.

    1. Building Secure Certificate Pinning by using Appdome’s DEV-API:

      1. Create and name the Fusion Set (security template) that will contain the Secure Certificate Pinning feature as shown below:
      2. fusion set that contains Secure Certificate Pinning

        Figure 1: Fusion Set that will contain the Secure Certificate Pinning feature
        Note: Naming the Fusion Set to correspond to the protection(s) selected is for illustration purposes only (not required).

      3. Follow the steps in Sections 2.2.1-2.2.2 of this article, Building the Secure Certificate Pinning feature via Appdome Console, to add the Secure Certificate Pinning feature to this Fusion Set.

      4. Open the Fusion Set Detail Summary by clicking the “...” symbol on the far-right corner of the Fusion Set, as shown in Figure 1 above, and get the Fusion Set ID from the Fusion Set Detail Summary (as shown below): fusion Set Detail Summary image

        Figure 2: Fusion Set Detail Summary
        Note: Annotating the Fusion Set to identify the protection(s) selected is optional only (not mandatory).

      5. Follow the instructions below to use the Fusion Set ID inside any standard mobile DevOps or CI/CD toolkit like Bitrise, App Center, Jenkins, Travis, Team City, Cirlce CI or other system:
        1. Build an API for the app – for instructions, see the tasks under Appdome API Reference Guide
        2. Look for sample APIs in Appdome’s GitHub Repository
    2. Building the Secure Certificate Pinning feature via Appdome Console

      To build the Secure Certificate Pinning protection by using Appdome Console, follow the instructions below.

      1. Where: Inside the Appdome Console, go to Build > Security Tab > Secure Communication section.
      2. When you select the Secure Certificate Pinning you'll notice that your Fusion Set you created in step 2.1.1 now bears the icon of the protection category that contains Secure Certificate Pinning

        Fusion Set applied Secure Certificate Pinning

        Figure 4: Fusion Set that displays the newly added Secure Certificate Pinning protection

      3. Extra Configuration with Secure Certificate Pinning:
        1. Enforce Certificate Roles

          Enforce network connections to verify 'basicConstraints' extension in the certificate chain.

        2. Enforce Strong RSA Signature

          Enforce server certificate signatures to use a Rivest-Shamir-Adleman (RSA) key with a length of at least 2048 bits.

        3. Enforce Strong ECC Signature

          Enforce server certificate signatures to use Elliptic-Curve Cryptography (ECC) key with a size of at least 256 bits.

        4. Enforce SHA256 Digest

          Enforce server certificate signatures to use at least a SHA256 certificate hashing algorithm.

      4. Click Build My App at the bottom of the Build Workflow (shown in Figure 3).
    Congratulations!  The Secure Certificate Pinning protection is now added to the mobile app

Using Appdome, there are no development or coding prerequisites to build secured Mobile Apps by using Secure Certificate Pinning. There is no SDK and no library to code or implement in the app and no gateway to deploy in your network. All protections are built into each app and the resulting app is self-defending and self-protecting.

Releasing and Publishing Mobile Apps with Secure Certificate Pinning

After successfully securing your app by using Appdome, there are several available options to complete your project, depending on your app lifecycle or workflow. These include:

If you have any questions, please send them our way at or via the chat window on the Appdome platform.

Thank you!

Thanks for visiting Appdome! Our mission is to secure every app on the planet by making mobile app security easy. We hope we’re living up to the mission with your project.

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