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Blog Security What Is a Digital Certificate? Definition and Meaning 


May 17 2023


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What Is a Digital Certificate?

A digital certificate verifies the identity of individuals, organizations, or devices online. It contains identifiable information about the certificate holder, such as their name, public key, and the digital signature of a trusted third party, known as a Certificate Authority (CA). Digital certificates are widely used for secure communication, authentication, and data encryption over the internet.

Digital Certification Definition

In cryptography, a public key certificate, also known as a digital or identity certificate, is an electronic document used to verify the validity of a public key.

A digital certificate certifies that a public key belongs to some entity, such as a user. The digital certificate contains the name of the subject, the public key, the name of the certification authority, the policy for using the private key corresponding to the public key being certified, and other parameters certified by the signature of the certification authority. The public key certificate is used to identify the subject and specify the operations that the subject is allowed to perform using the private key corresponding to the public key authenticated by this certificate.

Digital Certificate

If the signature is valid and the software that validates it trusts the certificate issuer, then it can use this key to securely communicate with the subject of the certificate.

In email encryption, code signing, and electronic signatures, the subject of a certificate is usually an individual or organization. However, in Transport Layer Security (TLS), the subject of a certificate is usually a computer or other device, although TLS certificates can identify organizations or individuals in addition to their primary role in identifying devices.

How Are Digital Certificates Used?

Certificates are typically used like electronic passwords to exchange encrypted data over large networks. A public key cryptosystem solves the problem of exchanging secret keys between participants in a secure exchange, but does not solve the problem of trust in public keys.

Suppose that Alice, wishing to receive encrypted messages, generates a pair of keys, one of which – the public key – she publishes in some way. Anyone who wants to send her a confidential message can encrypt it with this key, and be sure that only she (since only she has the corresponding secret key) can read this message. However, the described scheme cannot prevent Eve from creating a pair of keys and publishing his public key, passing it off as Alice’s key. In this case, Eve will be able to decrypt and read at least that part of the messages intended for Alice that were mistakenly encrypted with his public key.

The idea of ​​a certificate is to have a third party that is trusted by the other two parties in the information exchange. It is assumed that there are few such third parties, and their public keys are known to everyone in some way, for example, stored in the operating system or published in logs. Thus, forgery of a third party’s public key is easily detected.

Digital Certificate Use

Who Can Issue a Digital Certificate?

CA certification authorities issue digital certificates. The CA is the main component of the entire Public Key Infrastructure (PKI).

Since the public key of the CA is publicly known, anyone can decrypt the digital signature of the certificate with it and calculate the hash, comparing which with the digital signature of the certificate allows you to verify the validity of the certificate.

By establishing a correspondence between the public key and information identifying the owner of the key, the digital certificate eliminates the possibility of replacing the public key or violating its identification in order to send signed data and receive encrypted data by an attacker.

Certification path validation is performed using the so-called chain of trust, where the signing of certificates is performed by the private keys of certificates higher in the chain. Thus, the digital signature of a certificate is considered correct only when not only it is correct, but also the digital signatures of all certificates are verified in this process. The certificate at the top of the certificate hierarchy is called the root certificate.

Digital Certificates vs. Digital Signatures

Digital Signatures

A digital certificate is issued by a trusted third party which proves the sender’s identity to the receiver and the receiver’s identity to the sender. In other words, it verifies the identity of the certificate holder. The CA issues an encrypted digital certificate containing the applicant’s public key and a variety of other identification information.

A digital signature allows you to confirm the authorship of an electronic document. The signature is associated with both the author and the document itself using cryptographic methods and cannot be forged using conventional copying.

The currently widely used digital signature technology is based on asymmetric public key encryption and relies on the following principles:

It is possible to generate a pair of very large numbers – a public key and a private key – so that, knowing the public key, it is impossible to calculate the private key in a reasonable amount of time. The key generation mechanism is strictly defined and is well known. Each public key has a corresponding private key.

There are strong encryption methods that allow you to encrypt a message with a private key so that it can only be decrypted with a public key. The encryption mechanism is well known.

If an electronic document can be decrypted using a public key, then you can be sure that it was encrypted using a unique private key.

The digital signature ensures that the certificate cannot be tampered with. It is the result of a cryptographic hash function of the certificate data, encrypted with the CA’s private key. The CA’s public key is publicly known, so anyone can decrypt the certificate’s digital signature with it, then calculate the hash themselves and compare if the hashes match. If the hashes match, then the digital certification process was valid and there is no doubt that the public key belongs to the one with whom we are going to establish a connection.


Digital Signature

Digital Certificate


Digital signature is an attachment to a digital document that ensures its authenticity and integrity

Digital certificate is a file that ensures holder’s identity and provides security


Hashed value of original message is encrypted with sender’s secret key to generate the digital signature

Issued and managed by CA (Certifying Authority). It involves: Key Generation, Registration, Verification, Creation.

Security Services

Authenticity of Sender, integrity of the document and non-repudiation

Security and authenticity of certificate holder


Digital Signature Standard (DSS)

X.509 Standard Format

What Are the Different Types of Digital Certificates?

For security purposes, the following types of certificates are used:

  1. Code signing certificates. This type of digital certificate is used to sign downloaded software or data. They are signed by the software developer/publisher. They are intended to make sure that the program or file is genuine and created according to the publisher’s claim. They are especially useful for publishers who distribute their products through third party sites. Code signing certificates also prove that the uploaded file has not been modified.
  2. Client certificates. Digital IDs or client certificates are used to identify a person to another user, a person to a device, or a system to another computer system. Emails are a common case where the sender signs the message with an electronic signature and the recipient confirms the signature. Digital certificate authenticationof the sender and recipient is carried out using client certificates. Client certificates can serve as two-factor authentication when a user wants to access a restricted database or access a payment portal gateway where they will be prompted to enter their credentials and undergo further verification.
  3. Transport Layer Security/Secure Socket Layer (TLS/SSL) certificates. The server has TLS/SSL certificates installed. Such certificates are designed to ensure that all communications between the client and the server are private and encrypted. The server may be a web server, an application server, a mail server, an LDAP server, or another type of server that requires authentication to deliver or receive encrypted data. A website address secured with a TLS/SSL digital certification will start with “https://” instead of “http://” where the “s means that internet protocol HTTP is “secured”.

Digital Certificate Benefits

Digital certificate benefits are used not only by banks and financial organizations, payment systems, and government agencies but also by online stores and individual entrepreneurs.

What are the benefits of using a certificate for a business? Since using digital certificates, the transmitted data can be encrypted. In addition, a full business authentication procedure is applied, which gives users some confidence that their personal data, such as phone numbers and bank cards, will not fall into the wrong hands.

For example, an SSL certificate guarantees the protection of all information that the site exchanges with the user’s browser. And that protecting your business. This is especially important for financial transactions, online transactions. Indirect benefits – increased trust in your business, increased sales, and protection of business information.

Ultimately, an SSL certificate helps build customer trust. If they know that their information is protected, they are more likely to want to do business with your company.

Digital Certificate Limitations

Like all digital security methods, digital certificates have their limitations. These include:

  1. Degree of protection. Digital certificates, like public key infrastructure, rely on CAs. In the event of a compromised CA or unauthorized access to a root certificate, the consequences could affect all clients for which that CA issued certificates.
  2. Computational complexities of public-key cryptography. Since digital certificates are based on asymmetric cryptography, its disadvantages are also inherited. The main limitation here is the time it takes to perform cryptographic calculations.
  3. Compatibility with other digital infrastructure components. To integrate digital certificates, it is necessary to configure the interaction between the existing IT systems of the organization.
  4. Certificate management. Certificates have an expiration date and can also be compromised. And this is not to mention the fact that the processes of issuing new certificates are also a daily routine. Therefore, when using digital certificates, it is clearly necessary to allocate additional resources for their maintenance.

Criticisms of Digital Certificates

On June 21, 2011, the Dutch company VASCO Data Security International recorded a DigiNotar hack. Fox-IT, which specializes in investigations in the field of information security, at the request of the competent authorities, conducted an investigation into this hack. In August 2011, a fake certificate for *.google.com appeared on the Internet, with the help of which unknown persons viewed the mail of Gmail users from Iran. Then the fact of compromising the servers of the Dutch certificate authority DigiNotar was discovered, as well as fake certificates from Yahoo, Mozilla, Tor, and other sites. DigiNotar soon filed for bankruptcy and ceased operations, and DigiNotar certificates were revoked everywhere.

Fox-IT published an investigation report in 2012. As it turned out, the attackers gained full control over all eight DigiNotar CA servers long before the intrusion was discovered. The Demilitarized Zone server was first hacked on June 17, 2011. Later this system was used as a file exchange point between external systems and DigiNotar’s internal servers.

The DigiNotar hack cast doubt on the long-term viability of the main X.509 digital certificate standard.

Applications for Digital Certificates

Digital certificates bind an entity, such as an individual, organization, or system, to a specific public/private key pair. Digital certificates can be thought of as electronic credentials that verify the identity of an individual user, system, or organization.

Websites use digital certificates to create protected HTTPS connection authenticating their validity. They are also used in e-commerce to protect sensitive, identification, and financial information, in online shopping, stock trading, banking, gaming and many other fields. Another common use for digital certificates is for safe email communication.

Different types of digital certificates are used for different purposes such as the following:

  • Internet Mail Multipurpose Extension (S/MIME) digital certificates for signing email messages.
  • SSL and IPSec digital security certificates for authenticating network connections.
  • Smart card digital certificates for logging into personal computers.


Digital certificates play a vital role in ensuring the security and authenticity of online communication, transactions, and data exchange. By leveraging cryptography and trusted third-party authorities, digital certificates provide a robust mechanism for verifying the identity of individuals, organizations, and devices online, thereby enhancing the overall trust and confidence in digital ecosystems. Helenix has unique experience in tailoring cryptographic solutions to the needs of enterprises. You can learn more about our competencies in the Custom Development section.


Digital certificate creation requires a few steps. You need to generate a public-private key pair, provide identity proof to a trusted public Certificate Authority (CA), and submit the request securely online.

An example of a digital certificate is the SSL/TLS certificate used by websites to secure online communication and transactions. Other examples include code signing certificates and email certificates.

Digital certificates are validated through a process called certificate validation, which involves checking the certificate chain, verifying the digital signature, and ensuring the certificate has not expired or been revoked.

You can secure your digital certificates by storing them in a secure location with restricted access, using strong passwords and multi-factor authentication, and regularly renewing or updating them as required by the CA.