What is certificate pinning and how does it work?

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Imagine you are using your mobile banking app and have just completed a transaction. You want to keep that sensitive information safe, right?

This is where certificate binding comes into play. It is a security measure taken by application developers to ensure that your data is transmitted securely over the network.

But what is certificate pinning , and how exactly does it work? And are there any downsides you should be aware of? Let's take a closer look.

Table of contents

What is “certificate attachment”?
How does SSL Pinning work?
Benefits of SSL Pinning
SSL Pinning Issues
Alternatives to SSL Pinning
What is “certificate attachment”?
Certificate pinning is a security measure that associates a host with its expected digital certificate or public key . It includes techniques such as static or dynamic pinning, which allow the system to verify the host's identity.

Instead of relying solely on the standard system of checking mobile app development service whether a trusted CA signs the server's SSL certificate , certificate pinning hard-codes a specific certificate or its public key into the application. This ensures that the application will only accept that pre-approved certificate, reducing the risk of man-in-the-middle attacks , unauthorized server connections, and rogue CAs.

Techniques Used in SSL Pinning
Let's take a look at the techniques used in SSL Pinning, specifically Certificate and Public Key Pinning, so you can better understand how it works.




SSL Certificate Pinning : Embeds a specific SSL certificate directly into your application code, so that it will only trust and establish secure connections with the server if it presents that certificate. This approach improves security, but can create problems when renewing certificates.
Public Key Pinning : Focus on a more granular level by specifying and verifying only the public key extracted from the SSL certificate. This method provides more flexibility than certificate pinning, allowing you to more easily update certificates without changing your application code. If you only pin the public key, the rotated certificate typically retains the same public key.
Types of SSL Pinning
Both static and dynamic SSL pinning improve the security of communication between an app and a server. The difference lies in how iOS and Android app developers handle certificates. Static SSL pinning embeds the certificate into the app itself, while dynamic SSL pinning allows the app to renew the certificate over time.

Static SSL Pinning : The SSL certificate is hard-coded into the application itself. This method, while secure, does not allow certificates to be updated, which creates potential security issues. If the hard-coded certificate expires or is compromised, you will have to update the entire application to install a new SSL certificate. Therefore, static SSL pinning requires careful planning.
Dynamic SSL Pinning : This method offers a more flexible approach to certificate pinning, allowing them to be updated without requiring a complete rebuild of the application. Dynamic SSL Pinning retrieves the SSL certificate or public key at runtime and allows software applications to dynamically update the pinned certificates. It provides additional security by maintaining the integrity of the communication between the client and the server.