What Is Certificate Pinning? How does Certificate Pinning Work?

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What is Certificate Pinning

What Is Certificate Pinning?

Certificate pinning is a security measure where the client application checks against a copy known as the certificates the server is using.

On the other hand, this cross-platform server application can serve as a cert pinning client as it embeds the certificate issued to the server within the client application, and the client can then verify the validity of the certificate and ensure that it matches the one pinned down.

The purpose of this validation is to examine the most basic certificate attributes – expiration date and issuer – as well as compare the provided fingerprint to the one that is already stored in the client app.

The fingerprint is essentially an overly simplified structure of either the entire certificate or its public key. On the assumption that the matching fingerprints occur between the server and the client-side certificate, the data transmission is recognized as valid.

In the other case, a window of vulnerability is created where, in a Man-in-the-Middle attack, a third-party function can take place, or on the other hand, the connection will be rejected as a precautionary measure to prevent the transmission of such an attack.

Implementation of Certificate Pinning

Certificate pinning, which is a crucial security measure in client-server communication, can be executed through two primary methods: preloading or auto-pinning.

Preloading is a process that embeds the ticket for the verified certificate inside the application before the application is launched.

This adds another protective layer against possible hacking activities. This approach guarantees that the client app is furnished with a full set of certificates upon installation and commenced usage, which counters any potential risks at the initial stage.

On the other hand, with the automated pinning of certificates automatically, it offers a fresh way. With this method, the certificate is pinned dynamically during the initial call from the client to the server. However, the client application pushes it after retrieving it from the server during the initial transaction.

The pinning process helps achieve this robustness and adaptability because the client application may change its pinned certificate in case of the server’s reaction, and therefore, the SSL/TLS processes always make a secure connection possible in dynamic surroundings.

Because of the fact that preload and auto-pinning methods have both advantages and their consideration, the decision to apply them largely relies on application architecture, security requirements, and operational preferences.

Through the use of certificate pinning correctly, organizations can uphold the integrity of client-server trade and guard against different risks, including Man-in-the-Middle attacks.

How does Certificate Pinning Work?

Authentication of client-server communication by means of certificate pinning makes a strong proof of successful association with a particular SSL/TLS certificate and its public key.

The implementation of this requires having the server’s public key or its certificate embedded in the client application’s codebase or configuration. During the SSL/TLS handshake procedure, three stages are involved with the client being required to get the server certificate when it tries to set up a connection.

The client doesn’t check as before against the list of issued certificates by a trusted certificate authority (CA) – instead, it checks it against the embedded certificate data or its public key.

To escape the issue of storing the whole certificate or public key, a cryptographic fingerprint (a hash) of the certificate or its public key is calculated and stored in the client app.

During the handshake, the certificate that is being registered has its fingerprint and is compared with the stored one. If the print somehow matches, the connection is established that provides the normal communications.

In some cases, there is no match, and the attack is thus a potential security threat, such as a Man-in-the-Middle attack, the connection is rejected.

Generally, certificate pinning alleviates the threat of such spoofing attacks as certificate abuse consequently, the secure nature of client-server communication is promoted.

Pros of Certificate Pinning

Enhanced Security:

The use of a browser directly associating a unique SSL/TLS certificate or public key within a client-side application is one way of eliminating the risks of Man-in-the-Middle (MITM) attacks and unauthorized certificate substitutions.

This will protect clients’ information from interception, and the risk of it being altered or changed by unauthorized parties will become smaller.

Protection Against Compromised CAs:

The conventional approach towards the validation of certificates heavily depends on a record of authorities certified by trusted certificate authorities (CAs), which are vulnerable to misuse and may issue forged certificates.

Certificate pinning cuts down the dependency on CAs by explicitly mentioning the certificates or public keys that are trusted, thus minimizing the ill consequences of a breach of CSS on security.

Control Over Certificate Trust:

Through embedding certificates or public keys into the client application, the organizations gain a higher level of control against potentially unwanted certificates that their clients trust.

This makes possible more fine-grained oversight of certificates and audits of trust of the relationships, thus raising the overall security measures.

Improved Resilience:

It can be pinned firmly by an SSL/TLS certificate, which makes inter-server communication resilient and increases its availability, which is caused by certificates revoked or expired.

Indeed, since the application client is provided with certain certificates or public keys to be trusted, it would be less vulnerable to disruption caused by the certificate’s thorough rearrangement.

Compliance Requirements:

At times, the certificate pinning becomes a prerequisite while attempting to maintain compliance with regulations in certain industries or for further security and data protection like sensitive data.

Implementation of certificate pinning will also help meet the OWASP requirements listed among the top flaws in web applications.

Cons of Certificate Pinning

Maintenance Overhead:

Maintaining and updating the pinned certificates or public keys along with clients’ applications adds further burden on maintenance overhead.

Any acts of changing server certificates or public keys are to be followed by complementary updates of the client application, which may demand a lot of time and other resources.


Certificate pinning additionally brings complexity to the communication mechanism between a client and a server that is already defined by the client-server model, particularly where application server infrastructure or certificate changes are dynamic.

Certificate updates, expiration, and renewal involve multicomplex procedures and thus make deployment and maintenance difficult.

Potential for False Positives:

Inaccurate certificates pinning systems may include false positives.

These are valid server certificates which are rejected for the mismatches between pinned corresponding certificates and public keys. This prediction can result in a service outage or feature flaws for end users.

Single Point of Failure:

This type of certificate or public key pinning can introduce the risk of leakage or become infeasible, due to which trust relationships among all client applications using that trust may be disrupted.

Recommended: What is Cryptographic Failure? Real-life Examples, Prevention, Mitigation

Hence, it should be emphasized how one vulnerable point in the security architecture could eventually lead to a key management problem.

Limited Flexibility:

Certificate pinning is limited by the inconsistency of client-server communication protocols since the client application can only be connected to certain certificates or public keys.

This brings challenges in situations where servers need to be branded with new certificates, and applications need to talk to servers of different certificates.

Better Alternative for Certificate Pinning

The alternative for implementing the certificate pinning is a combined approach of Certificate Transparency (CT) logs interworking with dynamic certificate validation.

Certificate Transparency is one of the mechanisms that permits the supervising and auditing of SSL/TLS certificates that have been issued by the Certificate Authorities (CAs).

CT logs eliminate the need for fastening to specific certificates or keys, instead giving the overall function of tracing and neutralizing tampered or unauthorized certificates in real-time.

Dynamic certificate validation means that CRLs are constantly monitored by issuing and identifying all the newly issued certificates against a list of cp-certificate authorities or domain-based rules.

This method is based on CT logs which provide full transparency and visibility that are responsible for ensuring certificates’ authenticity besides the pinning functions.


As you’ve learned about certificate pinning and its role in ensuring secure client-server communication, now is the time to take proactive steps to enhance your organization’s security posture.

At Certera, we understand the critical importance of securing your digital assets and protecting sensitive data from evolving cybersecurity threats. Explore how Certera’s comprehensive security solutions can help you implement certificate pinning effectively and efficiently.

Janki Mehta

Janki Mehta

Janki Mehta is a passionate Cyber-Security Enthusiast who keenly monitors the latest developments in the Web/Cyber Security industry. She puts her knowledge into practice and helps web users by arming them with the necessary security measures to stay safe in the digital world.